401(k) Calculator

A 401k calculator runs a year-by-year compounding model. Every January, it adds your employee contribution, adds the employer match, applies your assumed annual return to the prior balance, and rolls the total forward. After 30 cycles, you get a projected ending balance. The math is the same future-value calculation you’d use for any investment, just layered on top of two contribution streams running simultaneously.

The inputs that move the projection the most are your contribution rate, your salary growth assumption, and your expected return. A 401k calculator that assumes you’ll always contribute the same flat dollar amount will lowball you. In real life, most people raise their deferral as their salary climbs, especially after they hit the 50+ catch-up threshold and unlock the extra $7,500, or the $11,250 super catch-up between ages 60 and 63. A calculator that lets you input a contribution as a percentage of salary will produce a more realistic picture than one that locks you into today’s dollar figure. We push clients toward percentage-based inputs every time we run the projection together.

The return assumption is where most people deceive themselves. A common default in a 401k calculator is 7% or 8%, drawn from the long-run S&P 500 average. That number includes reinvested dividends and ignores fees. If your plan’s expense ratios run 0.75% on the average fund (not unusual for older small-business plans), your real net return is closer to 6.25%. Over 30 years, that difference compounds into a six-figure gap. Run the calculator at 7%, then run it again at 5.5%, and look at the spread. That’s your fee-and-volatility margin of error, and it’s wider than most people are comfortable admitting.

Salary growth matters too. If you assume 3% annual raises and you’re contributing 10% of pay, your dollar contribution grows every year along with your salary. A 401k calculator that holds your salary flat undercounts the back end of the projection. The biggest dollar contributions you’ll ever make to a 401(k) are almost always in the last decade before retirement, when your salary is highest and you’re eligible for catch-ups. That’s also when bad market years hurt the most—sequence-of-returns risk doesn’t care about your average return. A 15% drawdown in your final working year erases a decade of careful contributions if the calculator wasn’t modeling that risk separately.

Some 401k calculators let you set a separate retirement-age return assumption to reflect a more conservative allocation as you approach 65. That’s closer to how target-date funds actually work. A glide path from 90% equities at age 35 to 50% equities at age 65 produces a lower terminal balance than a static 80/20 portfolio, but it also produces a much narrower range of outcomes. If you want the calculator to reflect that, you have to set the assumption manually—most defaults don’t do it for you. Monte Carlo simulators handle this properly; deterministic 401k calculators don’t.

Here’s the surprising part: contribution percentage matters more than return assumption, especially in the first 15 years. Going from 6% to 10% of salary contributed will outrun a half-point of extra return for most of your career. The single highest-impact input in any 401k calculator isn’t the market return—it’s the contribution rate. We’d rather see a client at 12% of pay assuming 6% returns than 6% of pay assuming 9% returns, even though the second projection looks bigger on paper. Reality has a way of punishing the second scenario and rewarding the first.

One last input most people forget: inflation. A projected balance of $2.5 million in 2056 dollars buys roughly $1.4 million of today’s purchasing power at 2.5% inflation. A 401k calculator that shows nominal dollars is fine for the math, but you have to translate it back into present-value terms before you decide whether you’re actually on track. The nominal number looks like a fortune. The real-dollar number looks like a comfortable retirement. Those are two very different feelings, even though they describe the same account.

One nuance the better 401k calculators handle: contributions don’t arrive in a January lump sum. They drip in over 24 or 26 pay periods. That dollar-cost-averaging effect smooths out volatility and slightly reduces sequence-of-returns risk in any given year. The terminal balance is roughly the same as the lump-sum assumption, but the path is less jagged. If your 401k calculator is averaging away that smoothing benefit, the projected range of outcomes is wider than your actual lived experience will be.

The market drawdown question deserves its own treatment. Historical S&P 500 returns include 2008 (-37%), 2002 (-22%), and 2022 (-18%) along with the boom years. A 401k calculator that quotes a 7% “average” smooths all of that into a flat line, but the actual path matters because you’re contributing and rebalancing along it. Two retirees with identical 30-year average returns can end with balances differing by 25% based on the order of returns alone. If you’re within 5 years of retirement and the calculator shows a single number, ask what the 10th and 90th percentile outcomes look like. The range is wider than the headline.

Bonuses and uneven income matter too. If you get a year-end bonus that’s 25% of base salary, and your plan defers from bonuses at the same rate as regular pay, your December contribution can be three or four times a normal month. A 401k calculator that models a steady monthly deposit will miss the lump-sum effect of bonus deferrals, especially the way they interact with the annual deferral cap. We’ve had clients hit the $23,500 limit in October because the December bonus took them over—the plan then refunded the excess, and the employer match got prorated. The calculator showed the full annual contribution. The actual deposit came up short.

We work through this kind of modeling with every retirement planning client—see our tax strategy consulting page or the full calculator hub for more tools. For the official rules behind the contribution limits the calculator should be using, see the IRS 401(k) Plan Overview.

A basic 401k calculator factors in the match percentage. Almost none of them factor in the vesting schedule, and that’s a real problem if you’re anywhere short of fully vested in your current employer’s match.

Start with the match itself. The most common employer match formula in the US is 50% of employee contributions up to 6% of salary—a 3% maximum employer contribution. A small but growing number of employers offer 100% match up to 4%, or even safe-harbor matches that hit 6% from the employer side. If you’re making $150,000 and contributing 10% of pay ($15,000), and your employer matches 50% up to 6% ($4,500), the 401k calculator should be adding $19,500 per year to your account, not $15,000. Plug the match number in correctly or the projection will be off by hundreds of thousands over a career.

Some employers also do a separate non-elective contribution—3% of pay deposited regardless of whether you contribute anything. Safe-harbor plans use this structure. If your plan has a 3% non-elective plus a 50%-up-to-6% match, you can earn 6% in total employer contributions on a 6% employee deferral. A 401k calculator that only asks for a single match percentage will miss the non-elective piece. Always check the Summary Plan Description and break out every employer contribution stream separately.

The total annual addition limit is also relevant if you’re a high earner with a generous match. In 2026, employee plus employer contributions cap at $70,000 (not counting age-based catch-ups, which sit on top). If you’re a partner at a small firm with a profit-sharing 401(k) and the employer contribution is 25% of compensation, you can hit that ceiling fast. A 401k calculator that lets you input separate employer and employee contributions will catch this; a calculator that just asks for a match percentage will quietly let you violate the limit on paper and produce a projection that overshoots reality by several thousand dollars per year.

Now the vesting piece. Federal law lets employers use one of two vesting schedules for matching contributions: a 3-year cliff (0% vested until year 3, then 100%) or a 6-year graded schedule (20% per year starting in year 2, fully vested at year 6). Safe-harbor matches must be immediately 100% vested, which is the only schedule that lets you ignore vesting entirely. Your own elective deferrals are always 100% yours from day one—the vesting rules only apply to employer money.

Almost no 401k calculator asks you about vesting. If you’re 18 months into a job with a 3-year cliff and you switch employers tomorrow, you walk away with zero of the employer match the calculator has been crediting to your balance. We’ve seen mid-career clients with three or four short-tenured jobs whose actual vested balance is 30-40% lower than what the projection assumed. The calculator was right about gross contributions. It was wrong about what was actually theirs to take with them on the way out the door.

The fix is to mentally discount the employer match in early years if you’re a likely job-changer. If you stay at jobs for an average of 3 years and your employer uses a 6-year graded schedule, you’re only locking in roughly 40% of the match before each move. Run the 401k calculator with the employer match reduced by 60% for the first decade of your career, then full match thereafter once you’ve settled into a longer-tenured role. The projection will look smaller, but it will be honest. We’d rather see an honest $1.8 million than a fictional $2.4 million.

One detail people miss: vesting credit usually accumulates based on plan-years, not calendar years. If you start work in November 2026, you might get a full year of vesting credit just for being employed through December 31. Read the plan’s Summary Plan Description before you make the call. Some plans use elapsed-time methods, some use 1,000-hour rules. The distinction can move a vesting date by months.

Forfeitures are another wrinkle. When an unvested employee leaves, their forfeited match goes back into the plan, where it’s either redistributed to remaining employees or used to offset future employer contributions. None of this shows up in your account, but it’s a reminder that the plan economics are zero-sum from the employer’s perspective. The vesting schedule isn’t generosity; it’s a retention tool. A 401k calculator that treats the match as guaranteed money ignores that retention math entirely.

The acceleration on certain events is worth knowing. Most plans accelerate vesting to 100% on death, disability, or attainment of normal retirement age (usually 65). If you’re 64 and contemplating an early retirement, sticking around to your 65th birthday in a plan with a 6-year graded schedule might be worth more than a year of salary. A 401k calculator can’t tell you that—you have to read the SPD and do the math by hand. Plan mergers and partial terminations (large layoffs) also trigger immediate full vesting under IRS rules. If your employer just announced a 25% workforce reduction, you may already be 100% vested whether you knew it or not.

Here’s the surprising part: the financial value of fully vesting before you leave is almost always larger than the salary bump from the next job. A client of ours was 4 months from a 3-year cliff worth $42,000. The recruiter wanted her to start in March. We told her to negotiate a May start date and an extra signing bonus to cover the gap. She did, and walked away with both. A 401k calculator can’t do that math for you, but it can show you what’s on the table—and that’s often the most important number a calculator produces. If you’re weighing a job change with significant unvested money, talk to us before you sign anything: new client inquiry or browse our helpful guides.

A 401k calculator shows different end balances for traditional vs. Roth because it’s comparing two different things: pre-tax money versus after-tax money. Side by side, the headline balance for a traditional account will almost always look bigger. After you account for the taxes you’ll eventually owe, the gap shrinks or disappears entirely.

Here’s the structure. Traditional 401(k) contributions come out of your paycheck before federal income tax. If you defer $23,500 and you’re in the 32% federal bracket, you reduce your current-year federal tax bill by $7,520. State tax savings stack on top of that—another $1,400 or so in New York City for a high earner. That $23,500 grows tax-deferred. When you withdraw it in retirement, the entire withdrawal is taxed as ordinary income. The IRS gets paid eventually, just at retirement-bracket rates instead of working-years rates.

Roth 401(k) contributions come out after tax. The same $23,500 deferral costs you the full $23,500 in spendable income today (because you already paid the $7,520 of federal tax on it). That money grows tax-free. Qualified withdrawals in retirement—after age 59½ and with the account at least 5 years old—come out entirely tax-free, both contributions and growth. There’s no required minimum distribution from a Roth 401(k) once you roll it into a Roth IRA at retirement, which extends the tax-free compounding indefinitely.

A naive 401k calculator just shows the gross balance. If you contribute $23,500 a year for 30 years at 7%, you end up at roughly $2.4 million in either bucket. The traditional projection then ignores that you owe taxes on every dollar of withdrawal. The Roth projection accurately shows that what you see is what you keep. Good 401k calculators offer a toggle to show after-tax-equivalent balances, which is the only fair comparison. Without that toggle, the calculator is misleading you about the actual size of your retirement.

The real question isn’t which account ends up bigger. It’s whether your marginal tax rate today is higher or lower than what your effective tax rate will be in retirement. If you’re a high earner in your peak years (think 32% or 35% federal bracket plus 6-13% state), traditional is usually the better call—you’re likely to be in a lower bracket pulling income in retirement, even if rates rise modestly. If you’re early career, in the 12% or 22% bracket, Roth is often better because you’re locking in today’s low rate against a probable future where you’ll be earning more and taxed harder.

The 2026 SECURE 2.0 rule changes the math for high earners in a way most 401k calculators haven’t caught up with yet. Starting in 2026, if your prior-year wages from the same employer exceeded $145,000, any catch-up contributions you make (the $7,500 standard catch-up at age 50+ or the $11,250 super catch-up at ages 60-63) must be Roth contributions. You can’t choose. That means a $145K+ earner doing the full $35,000 contribution at age 55 has $23,500 going traditional (pre-tax) and $11,500 forced into Roth. The 401k calculator needs to model both buckets separately—and most of them don’t.

Surprising point: the case for Roth gets stronger the higher your retirement balance gets. Once you’re looking at a $5 million traditional balance, the required minimum distributions starting at age 73 push you into the same brackets you were trying to escape. RMDs don’t apply to Roth 401(k)s for the original owner once you roll them to a Roth IRA, which means a Roth dollar in retirement can sit untouched indefinitely. For the HNW saver, that flexibility is often worth more than the brief tax savings of choosing traditional. We’ve had clients in their late 60s wishing they’d done more Roth in their 40s for exactly this reason.

The estate-planning angle pushes the same direction. A Roth 401(k) or Roth IRA inherited by a non-spouse beneficiary still has to be distributed within 10 years under SECURE Act rules, but every dollar comes out tax-free. A traditional 401(k) inherited the same way generates 10 years of ordinary-income tax for the beneficiary, who is probably in their own peak earning years. For wealthy households planning a generational transfer, Roth accounts are simply worth more after the second death.

State income tax also tilts the math. New York City taxes high earners at roughly 13% combined state and local. Florida and Texas tax retirees at zero. If you’re a NYC professional planning to retire to Florida, your effective state tax rate is going to drop from 13% to 0% the day you change residency. That alone is a strong argument for traditional contributions during your NYC working years, because you’ll deduct against 13% state tax now and pull dollars out at 0% state tax later. The 401k calculator doesn’t know your relocation plans. You do.

The other complicating factor is in-plan Roth conversions and the mega backdoor strategy. If your plan allows after-tax (non-Roth, non-traditional) contributions up to the $70,000 total limit and allows in-service conversions or in-plan Roth rollovers, you can stuff an additional $35,000-$40,000 a year into Roth treatment beyond the elective deferral cap. Almost no 401k calculator models this. We do it manually for our high-net-worth clients who have access to a plan that allows it.

The breakeven analysis on traditional vs. Roth is sensitive to two assumptions: your current marginal rate and your retirement marginal rate. If you think rates will be the same in retirement as today, the two accounts produce mathematically identical after-tax wealth, assuming the same investments. The actual deciding factor is then everything outside the math—RMD avoidance, state-of-residence change, estate planning, tax-bracket optionality. A 401k calculator that only compares end balances misses the entire reason most planners now lean Roth for high earners despite the higher current-year cost.

For most people, the right split is some of both. Hold the traditional for current-year deduction value, hold the Roth for tax diversification in retirement. Aim for a balance that gives you enough pre-tax money to fill the standard deduction and lower brackets in retirement, and enough Roth money to handle the years where you need a big withdrawal without spiking your bracket. See our tax strategy guides for the full conversation.

Some can, most can’t. A 401k calculator built before SECURE 2.0 took full effect is almost certainly running on 2024 or 2025 numbers, and the 2026 changes are big enough that the answer comes out wrong. Here’s what the calculator needs to know to be accurate this year, and why it matters for the projection it spits out.

The 2026 elective deferral limit is $23,500. That’s the same as 2025 (the IRS held the limit flat after the 2024 bump from $23,000). The standard catch-up contribution for employees age 50 and over is $7,500, bringing the total to $31,000 for that group. So far, this is just incremental inflation adjustment and most 401k calculators handle it correctly if they’ve been updated since fall 2024.

What’s new for 2026 is the super catch-up. SECURE 2.0 created a higher catch-up tier for employees aged 60, 61, 62, and 63. For those four years, the catch-up jumps from $7,500 to $11,250. That puts the total deferral ceiling for a 61-year-old at $34,750 ($23,500 base + $11,250 super catch-up). The moment you turn 64, you drop back to the standard $7,500 catch-up. A 401k calculator that doesn’t model this four-year window will undercount what you can defer between ages 60 and 63—potentially by $15,000 over the four years. For a HNW saver hitting their peak earning years right at retirement, that’s real money that compounds over the remaining decade or two of growth.

The total annual addition limit (employee deferrals + employer match + profit sharing + after-tax) for 2026 is $70,000, not counting catch-ups. With catch-ups added, the cap goes to $77,500 for age 50+ and $81,250 for age 60-63. This matters most for owner-employees with profit-sharing 401(k)s and for anyone using the mega backdoor Roth strategy. If you’re a sole proprietor with a Solo 401(k) doing the maximum employee deferral plus the maximum employer profit-sharing contribution, that ceiling is the binding constraint on how much you can put away each year.

Then there’s the SECURE 2.0 Roth catch-up requirement, which is the change that’s tripped up the most plans. Starting in 2026, if you earned more than $145,000 in prior-year wages from the same employer that sponsors your 401(k), any catch-up contributions you make—both the $7,500 standard and the $11,250 super catch-up—must go into a Roth account. You don’t get to choose pre-tax. The base $23,500 elective deferral can still be traditional or Roth at your option, but the catch-up dollars are Roth-mandatory for high earners. The wage threshold uses prior-year wages from that specific employer, so a person who switches jobs mid-year may not trigger the rule until the year after.

A 401k calculator that doesn’t know about the Roth catch-up rule will either let you assume all catch-up contributions are pre-tax (overstating current-year tax savings) or won’t differentiate the tax treatment at all. For a $145K+ earner at age 55, that’s a $7,500-per-year pre-tax deduction the calculator is showing that doesn’t actually exist. Over 10 years, that’s $24,000 of phantom current-year tax savings at the 32% bracket. We’ve had clients adjust their withholding based on a bad calculator output and then owe at filing time because the rule changed under them.

The wage definition is worth a closer look because it’s caused confusion. The $145,000 threshold is based on Social Security wages reported on the W-2 in box 3 from the same employer that sponsors the 401(k). Self-employment income doesn’t count toward the threshold, and wages from different employers aren’t aggregated. A consultant who works for two companies and earns $100,000 at each one is not subject to the Roth catch-up rule even though total compensation is $200,000. The same person earning $200,000 at one job is. The single-employer test creates planning opportunities for people with multiple income sources.

Inflation adjustments are baked into the law going forward. The $145,000 high-earner threshold for the Roth catch-up rule is indexed to inflation in $5,000 increments. The deferral limits adjust in $500 increments. The total annual addition limit adjusts in $1,000 increments. A 401k calculator that quotes a hard 2026 number for a 2035 projection is using stale data for two-thirds of the projection. The better tools index the limits forward at an assumed inflation rate so the projection stays internally consistent.

Surprising point: if your employer’s plan doesn’t offer a Roth option at all, the SECURE 2.0 rule means high earners can’t make any catch-up contributions in that plan. Either the plan adds a Roth feature or the catch-up dollars disappear. Most plans have scrambled to add Roth provisions to avoid losing high-earner catch-ups entirely. If yours hasn’t, that’s a question for HR. We’ve had clients where the answer drove a job change—an extra $7,500 a year of catch-up at age 55, compounding to 65, is worth roughly $120,000 in additional retirement wealth.

The other 2026 wrinkles worth modeling in a 401k calculator: automatic enrollment is now required for new 401(k) plans (existing plans grandfathered), and emergency savings accounts can be linked to 401(k)s at the employer’s option, with limited withdrawals before age 59½ without penalty. Neither directly changes the contribution math, but both can change how much actually lands in the deferral bucket month to month.

The SECURE 2.0 student-loan match provision is another one worth knowing about. Starting in 2024, employers can treat qualified student-loan payments as if they were 401(k) contributions for purposes of the employer match. A younger employee paying $500/month on student loans can get the full employer match without contributing a dime of payroll into the 401(k). A 401k calculator that lets you input the student-loan match amount as a separate stream will catch this; most don’t. If you’re early career with significant loan debt, ask your plan administrator whether the feature is offered.

For the official numbers, see the IRS announcement on 2025 retirement plan limits (the 2026 figures track closely) and the broader IRS 401(k) Plan Overview. If you want a calculator that handles the super catch-up and the Roth catch-up requirement together, you’ll likely have to build a spreadsheet or work with a planner. We do this kind of modeling for clients in our tax services.

A 401k calculator is the right tool to start the rollover conversation, but it’s rarely the only tool you need. The decision is partly numerical and partly about features and protections that don’t show up in a balance projection.

Run the 401k calculator first to confirm what you actually have. Pull your most recent statement, separate the elective deferral balance from the employer match balance, and check the vesting status on the match. If you have unvested employer contributions, leaving them in the plan until you vest is the obvious move—an IRA can’t accept money that isn’t yours yet. Sometimes the right answer is to delay the rollover for 6-18 months to fully vest, then move everything. We’ve had clients hold off six months on a rollover and pick up another $30,000 of vested match they would have walked away from.

Now compare costs. A 401k calculator that lets you adjust the expense ratio will show you the long-run cost difference. The average 401(k) expense ratio at large employers is around 0.30-0.50% all-in. At small employers with old plans, it can run 1.0% or higher. A typical Vanguard or Fidelity rollover IRA invested in index funds runs 0.03-0.10%. Over 25 years on a $400,000 balance, the difference between a 0.75% plan and a 0.05% IRA is roughly $90,000 in cumulative fees. That number alone makes a strong case for rolling out of an expensive plan after you separate from service.

Run the 401k calculator twice: once with your plan’s current expense ratio and contribution stopped (since you can’t contribute to a former employer’s 401(k)), once with the IRA expense ratio. The starting balance is identical; only the drag changes. The gap at retirement is what the rollover is buying you in lower fees. If the gap is tiny—say, you’re in a Fidelity plan with institutional share classes running 0.04%—the fee case for rolling out evaporates. Check before you assume.

But fees aren’t the whole story. There are at least four reasons to leave money in a 401(k) instead of rolling it. First, the rule of 55: if you separate from service in the calendar year you turn 55 or later, you can take penalty-free withdrawals from that specific 401(k) without the 10% early-withdrawal penalty. Roll it to an IRA and that benefit disappears—you’re back to the standard 59½ rule. For someone planning early retirement, this matters a lot. We’ve had clients lose access to penalty-free withdrawals they didn’t realize they had by rolling at age 56.

Second, creditor protection. 401(k) balances have federal ERISA protection from creditors and lawsuit judgments. Rollover IRAs get state-law protection, which varies. New York protects IRAs reasonably well; some states don’t. If you have any reason to worry about future liability (high-income physician, real estate investor, anyone with personal guarantees on business debt), the ERISA shield is worth keeping. A 401k calculator won’t show this as a number, but a $1.5 million lawsuit judgment hitting an IRA in the wrong state can wipe out everything the calculator projected.

Third, the backdoor Roth IRA strategy. If you ever want to do backdoor Roth conversions, having pre-tax money in an IRA triggers the pro-rata rule and partially taxes every conversion. Pre-tax money sitting in a 401(k) doesn’t count toward the pro-rata calculation. We routinely tell high earners to leave their 401(k) balance in the plan specifically to keep the backdoor Roth pathway clean. Run our Roth IRA calculator alongside the 401k calculator to see what’s at stake. A $7,000 annual backdoor Roth, compounded for 25 years at 6%, lands at about $390,000 of tax-free money. That’s the prize you protect by leaving your traditional 401(k) alone.

Fourth, in-plan Roth conversions and stable value funds. Some plans offer features you can’t replicate in an IRA, like stable value funds (a guaranteed-rate option that often pays 3-4% with no principal risk) or institutional-share-class funds you can’t access retail. If your old plan has either, the rollover math gets more interesting. A 401k calculator that treats all dollars as equivalent misses the value of plan-specific features that can’t be transported.

Loan provisions are another piece. A 401(k) typically lets you borrow up to 50% of your vested balance (capped at $50,000) and pay yourself back over five years. IRAs don’t allow loans of any kind. If you ever anticipate needing access to a portion of your retirement balance without triggering taxes and penalties, the 401(k) loan feature is worth keeping. We don’t recommend treating retirement money as a piggy bank, but for a one-time bridge during a job transition or a real estate transaction, it can be a useful tool that disappears the moment you roll to an IRA.

Surprising point: rolling a 401(k) into a new employer’s 401(k) is often a better move than rolling it to an IRA. Most people skip this option because it requires paperwork and the new plan has to accept rollovers (most do). But it preserves ERISA protection, keeps pre-tax money out of your IRA for backdoor purposes, and consolidates your accounts. The 401k calculator shows you the balance growth; the rollover strategy is about preserving optionality you can’t buy back later.

The timing of the rollover also matters for tax reasons most people don’t think about. If you do a direct trustee-to-trustee rollover, there’s no withholding and no risk. If you take a distribution and try to roll it within 60 days, your former employer is required to withhold 20% for federal taxes. To complete a tax-free rollover, you have to come up with that 20% from outside money and deposit the full original balance into the IRA within the window. People botch this every year and end up with a taxable distribution they didn’t intend. Always do trustee-to-trustee.

One last thing the calculator won’t catch: if your 401(k) holds employer stock with significant appreciation, you may qualify for net unrealized appreciation (NUA) treatment, which lets you pay long-term capital gains rates on the appreciation instead of ordinary income rates. Once you roll the stock into an IRA, NUA is gone forever. This is one of the most expensive mistakes people make at retirement. If you have employer stock in your 401(k), talk to us before you initiate a rollover: new client inquiry.