401(k) Calculator
Salary, contribution, and the employer match — see what compounding turns it into by retirement.
How this is calculated
FV = B(1+r)ⁿ + (C + M) × ((1+r)ⁿ − 1) ÷ r where r = return ÷ 12, n = years × 12, C = your monthly deposit, M = employer match
Worked example: $25,000 balance, $70,000 salary, 6% contribution, 6% match, 7% return, 30 years. You put in $350/month, your employer adds another $350 — $8,400 a year, half of it free. Over 30 years that grows to roughly $1.05 million: about $126,000 of your money, $126,000 of employer match, and the rest — the vast majority — pure compounding.
The one rule that matters most
Always contribute at least enough to get the full employer match — it's an instant 100% return no investment can beat. Skipping it leaves guaranteed money on the table every payday. After that, time does the heavy lifting: start ten years earlier and the growth portion more than doubles.
The honest caveats
This projects a steady return; real markets swing. The balance shown is pre-tax — a traditional 401(k) is taxed on withdrawal, so treat part of the final number as deferred tax. Contribution limits apply (the IRS caps annual 401(k) deferrals), and fees quietly reduce real-world growth. Use it to see the shape, not to predict a cent.
Frequently asked questions
How does the employer match work here?
Most US employers match your contribution up to a share of your salary — commonly “100% up to 6%.” This calculator adds an employer deposit equal to your contribution rate, capped at the “employer match” percentage you set. If you contribute 6% and the match caps at 6%, the employer adds another 6% of salary — free money that compounds alongside your own.
What return should I assume?
The long-run US stock market has averaged roughly 7% a year after inflation (about 10% before it). 7% is a sensible planning default, but it is not a promise — markets fall as well as rise. Use a lower number if you want a conservative projection, and remember the result is in today-ish dollars only if you treat the rate as real (after inflation).
Is this a traditional or Roth 401(k)?
The growth math is identical. The difference is tax: a traditional 401(k) is taxed when you withdraw in retirement, a Roth is taxed now and withdrawn tax-free. This tool shows the pre-tax balance either way — for a traditional account, remember a chunk of the final number is the taxman’s.
Is anything I type sent anywhere?
No. Salary, balance and every number are computed entirely in your browser and never uploaded. The page works offline once loaded.