401k Calculator

Project your 401k at retirement from monthly contributions, employer match, raises and compound growth. See projected balance, principal and growth.

All calculations happen locally in your browser. Nothing leaves your device.

Balance at retirement
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Total principal
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Total growth
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Future value of contributions
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How It Works

Compound growth is the engine behind a 401k. Each month your balance earns interest at your chosen annual return divided by 12, and then your contribution and your employer's match are added. Because the interest itself becomes part of the balance and earns interest again, the curve bends upward — small early differences in balance snowball into large gaps by retirement.

Compound growth
Your balance grows as balance × (1 + monthly rate) every month. Starting $50,000 at a 7% annual return roughly doubles every 10 years, and adding monthly contributions on top more than triples the eventual amount versus letting the starting balance grow alone.
Employer match
The match is free money: the tool applies your match percentage to each monthly contribution, capped at 5% of your monthly salary (for a 5% match, $25 per $500 contributed, up to 5% of pay). Capturing the full match is the single highest-return move you can make — you earn a guaranteed 100% return on those dollars before any market growth.
Rising salary
Your salary increases by the annual raise each year, and the match cap (a percentage of pay) rises with it. This keeps the projection realistic as your income — and typically your contributions — grow over the years to retirement.

Frequently Asked Questions

How does the 401k balance grow over time?

The tool grows your account month by month. Each month your balance earns interest (your chosen annual return ÷ 12) and then your monthly contribution and your employer's match are added. Because earnings are added to the balance and earn interest in later months, the growth compounds — the later your money lands, the less time it has to compound, which is why starting early dominates.

How does the employer match work?

Most employers match a percentage of what you contribute, up to a cap. For example a 5% match means your employer adds $0.05 for every dollar you put in, typically capped at 5% of your salary. This tool applies your match percentage to your monthly contribution and caps the monthly match at 5% of your monthly salary. The match is free money — you should always contribute at least enough to capture it fully.

What return should I assume?

A common long-run assumption is about 6–8% before inflation, based on historical stock-market averages. Use a higher number only if you are comfortable with more risk; use a lower one if your mix is conservative or you want a conservative estimate. The result is very sensitive to this figure over 30+ years, so treat the output as a projection, not a promise.

Why does the tool account for annual raises?

Your salary grows each year, and the employer match is tied to your salary (the cap is a percentage of pay). Raising your salary also usually means raising your contributions, so the monthly match can increase over time. The tool grows your salary by your annual raise percentage and recomputes the match each year so the projection reflects a realistic, growing income.

Is this accurate?

It is a projection, not a forecast. Actual returns depend on market performance, and fees, taxes, contribution limits and plan rules all affect the real outcome. The numbers here assume a constant return, fixed contributions and no fees, so use them for planning and comparison rather than as a precise target.