401(k) Calculator
Contributing $500 a month to a 401(k) with a $20,000 balance, a 50% employer match up to 6% of a $90,000 salary, and a 7% annual return grows to about $1,046,800 in 30 years. Of that, $180,000 is your own contributions, $81,000 is the employer match and $765,800 is pure growth.
The employer match is the only guaranteed 50% return in personal finance. This calculator shows exactly what skipping it costs.
The match is salary you have already earned. On a $90,000 salary with a 50% match up to 6%, contributing $450 a month pulls in $225 of employer money every month. Contributing only $150 instead leaves $150 a month of free money — $54,000 over a 30-year career, before growth.
Calculator
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How This Calculator Works
The balance compounds monthly at your expected return. Every month adds your contribution plus the employer match, which pays matchPct of each dollar you defer, up to capPct of salary.
A 50% match up to 6% of salary therefore pays $0.50 per dollar deferred, on at most $450 of deferral at a $90,000 salary. Contribute more than the cap and the extra still grows — but earns no match.
FV = B(1+r)n + C·((1+r)n − 1)/r + Match·((1+r)n − 1)/r — r = return/12, n = months
Worked example
Using the defaults — $20,000 saved, $500 a month deferred, $90,000 salary, 50% match up to 6%, 7% return, 30 years:
The 6% cap on a $90,000 salary is $450 a month. Your $500 deferral is $50 more than the cap, so the match pays 50% of $450 = $225 a month, or $81,000 over 30 years.
Your contributions ($180,000) plus match ($81,000) total $261,000. The balance reaches about $1,046,800 — compounding supplies the remaining $765,800, three quarters of the final number.
Cut the contribution to $150 and the balance falls to about $436,800 — $610,000 less at retirement in exchange for $350 a month of take-home pay today.
The calculator compounds monthly and holds the return, salary and match policy constant. Real plans also have vesting schedules, fund fees, and contribution limits that change most years.
The same plan across horizons
Time in the market dominates every other input. The last decade contributes more than the first two combined.
| Years | Balance | Your contributions | Employer match | Growth |
|---|---|---|---|---|
| 10 | $165,680 | $60,000 | $27,000 | $58,680 |
| 20 | $458,447 | $120,000 | $54,000 | $264,447 |
| 30 | $1,046,809 | $180,000 | $81,000 | $765,809 |
| 40 | $2,229,218 | $240,000 | $108,000 | $1,861,218 |
Between year 30 and year 40 the balance more than doubles while contributions rise by only a third. This is the argument for starting early that no sales pitch improves on.
Common mistakes with this calculation
- Contributing below the match cap. Every dollar under the cap forfeits the match permanently. At a 50% match, contributing $300 instead of the full $450 cap on a $90,000 salary hands back $75 a month — roughly $27,000 over 30 years before growth.
- Cashing out when changing jobs. A $50,000 balance cashed out early loses years of compounding plus taxes and the 10% early-withdrawal penalty. Rolling it into an IRA or the new plan preserves the trajectory.
- Ignoring fees. A 1% annual fee versus 0.1% on the same contributions is roughly $170,000 of difference over 30 years on this plan. Fees are the one input you control directly.
- Assuming the match vests immediately. Many plans vest employer money over three to six years. Leaving early forfeits the unvested part regardless of what the calculator shows.
When this calculator does not apply
- Taxes are not modelled: a traditional 401(k) defers income tax to withdrawal, while a Roth 401(k) taxes contributions now. The balance is pre-tax in the traditional case.
- The expected return is held constant. Real returns vary, and the sequence of returns near retirement changes the outcome.
- The model does not include salary growth, catch-up contributions after age 50, or changes to IRS contribution limits.
- Withdrawal rules, required minimum distributions and early-withdrawal penalties are outside the projection.
- Inflation is not subtracted. $1,046,800 in 30 years at 2.5% inflation spends like about $500,000 today.
Frequently Asked Questions
How much should I contribute to my 401(k)?
At minimum, the full employer match, because it is an instant 50% return on that slice. Beyond the match, a common target is 15% of gross salary across all retirement accounts, counting the match.
Is the employer match really free money?
It is compensation you earn by working, paid only if you defer your own money. Unlike a market return it is guaranteed by the plan terms, which is why capturing it fully is the first financial priority for most earners.
What happens to my 401(k) when I change jobs?
You can leave it, roll it into your new employer plan, roll it into an IRA, or cash out. Cashing out triggers income tax plus a 10% penalty before age 55 in most cases, and forfeits unvested employer money.
Traditional or Roth 401(k)?
Traditional cuts your taxable income now and taxes withdrawals later; Roth taxes contributions now and lets withdrawals grow tax-free. If your tax rate at withdrawal will be higher than today, Roth usually wins; if lower, traditional usually wins.
Sources & Methodology
This calculator uses standard financial formulas. See our methodology page for the full derivation.
- 401(k) plan contribution limits Internal Revenue Service
- 401(k) Plans U.S. Department of Labor
- Retirement Tools Consumer Financial Protection Bureau
Last reviewed .
Key takeaways
- $500 a month with a full match and 7% return reaches about $1,046,800 in 30 years.
- The employer match contributes $81,000 of that — and grows to far more once invested.
- Growth supplies roughly three quarters of the final balance; contributions only a quarter.
- Never leave match money on the table: it is a guaranteed 50% return.
- Fees of 1% versus 0.1% can swing the outcome by six figures.