401(k) Calculator

What does a 401(k) calculator work out?

A 401(k) calculator projects what your account could be worth at retirement from four things: the balance you have now, the share of each paycheck you contribute, the employer match your plan adds on top, and an assumed annual return.

It compounds all three sources year by year, applies the match rule your plan states, and checks each year's contribution against the IRS limit for your age, so you can see how much of the final balance is your money, your employer's, and growth.

At the defaults — age 30, a $70,000 salary, a $10,000 balance, 6% contributed, a 50%-of-6% match and 7% a year — the balance at 65 is $1,060,615: $10,000 starting balance, $147,000 of your contributions, $73,500 of employer match and $830,115 of growth. The chart stacks those four slices by age so the proportions are visible, not just the total.

How does a 401(k) employer match work?

The most common 401(k) match is "50% of the first 6% of salary." On a $70,000 salary, contributing 6% ($4,200 a year) triggers a $2,100 employer match — a 50% instant return on those dollars before any market gains. Contribute only 3% and you capture half the match: $1,050 of compensation a year stays with your employer.

Over 35 years at a 7% return that unclaimed $1,050 a year compounds to about $157,600 of balance (at the defaults, 3% instead of 6% ends at $587,838 instead of $1,060,615). The match line in this calculator makes that cost visible. The match is applied to the matched share of pay, not to the contribution: a 10% contribution on a 50%-of-6% plan still earns a match on 6% of salary.

Match dollars follow your plan's vesting schedule, which this calculator does not model. Some plans vest immediately; others use cliff or graded schedules that phase in ownership over two to six years. Your Summary Plan Description has the rule.

What are the 401(k) contribution limits for 2026?

The Internal Revenue Service sets the limits each year under §415(d) of the tax code. For 2026 (IRS Notice 2025-67) the elective deferral limit is $24,500. From the year you turn 50 you may add an $8,000 catch-up, for $32,500 in total; at ages 60 through 63 the SECURE 2.0 §109 catch-up is $11,250, for $35,750.

The calculator reads these limits from its dataset and labels the year. They apply to your own deferrals only — employer match dollars do not count against them. The combined limit for everything going into your account (your deferrals plus all employer contributions) is $72,000 for 2026 under §415(c), and compensation above $360,000 cannot be counted in a plan formula under §401(a)(17). Most employees are nowhere near either ceiling.

When a projection year's contribution exceeds the limit for the age you reach that year, a note appears beside the fields. It does not cap the estimate — your plan administrator stops deferrals at the statutory limit — and it holds the 2026 limit flat for every future year because the IRS indexes it annually by amounts that cannot be known in advance.

Should I use a traditional or a Roth 401(k)?

Traditional 401(k) contributions reduce your taxable income now and are taxed on withdrawal. Roth 401(k) contributions are after-tax, so qualified withdrawals in retirement are tax-free. The deferral limit is the same for both and is shared between them; a Roth dollar costs more today because it is paid after tax.

Which is better depends on whether your marginal rate now is higher or lower than your rate in retirement — a question this calculator cannot answer because it does not see your tax picture. This page models the nominal balance only; the IRA calculator on this site runs the equal-after-tax-cost comparison, and the Roth conversion calculator models the tax on moving money across.

How much will my 401(k) be worth in 20 years?

The return assumption is the biggest driver. At the defaults the balance at 65 is $1,060,615 at 7%; at 5% it is $653,786 and at 9% it is $1,775,071 — a two-point change in the rate moves the answer by roughly $400,000 each way, which is why the scenario strip shows all three.

Starting the same inputs at age 45 instead of 30 gives $313,874 after 20 years; at 55 it gives $110,966 after 10.

Fees compound against you the same way returns compound for you. A 1% annual fee on the default inputs cuts the balance at 65 from $1,060,615 to $829,208 — $231,407 less, not the $10,600 a one-year 1% charge would suggest. Enter your plan's expense ratio under Advanced to see its full long-run cost.

Enter a return as a nominal figure if you want nominal output; set an inflation rate under Advanced to see the same balance in today's dollars (at 3% inflation the default $1,060,615 is worth $376,925 today). A diversified US equity portfolio has returned roughly 10% a year nominal before fees over long periods and a blended portfolio is often assumed at 6–7%; neither is guaranteed and the calculator's result is a scenario, not a forecast.

What does this 401(k) estimate leave out?

This calculator uses a constant salary growth rate, a constant return and a constant contribution percentage for the whole accumulation period. Real careers have gaps, job changes, salary jumps and market cycles that one compound-growth formula cannot capture. Contributions are credited at the end of each month, so a lump sum paid in January would grow slightly more than shown.

It does not model withdrawals before retirement, required minimum distributions, Social Security, pension income, the tax on distributions, the §415(c) combined limit or the vesting of the match.

This calculator gives an estimate under the assumptions you enter — the return, salary growth and contribution figures are yours, and the IRS figures are the published ones for the year shown. It is not financial, tax or investment advice and not a prediction; markets, the law and your circumstances will differ. Your plan administrator holds your actual figures.