About this tool
Pension / 401k Contribution Calculator is a free, in-browser tool that projects a workplace retirement pot from your salary, your contribution percentage, and your employer's matching policy, with salary growth and investment returns compounding year by year. Nothing leaves your browser.
Each year the employer adds match% of whatever you contribute, but only up to the match cap (a percentage of salary) — the standard "100% match up to 5%" structure. The balance grows by the annual return, contributions are added, and your salary rises by the growth rate for the next year. If you contribute below the cap, the tool highlights the free match money you are leaving on the table in the first year.
Use it to see the long-run cost of not maxing your match, or to project your pot at retirement under different return assumptions.
Frequently asked questions
How does the employer match work here?
Employer contribution = salary × min(your %, match cap %) × match rate. With a 100% match rate and 5% cap, contributing 5% doubles your money; contributing 8% still only earns a 5% match; contributing 3% wastes 2% of salary in free match.
What does 'match left on the table' mean?
If your contribution percentage is below the cap, it shows the first-year employer money you forfeit: salary × (cap − your %) × match rate. Raising your contribution to at least the cap is usually the highest-return move in personal finance.
What are the timing conventions?
The projection is annual: the opening balance grows by the return for the year, then the year's employee and employer contributions are added, then salary is increased by the growth rate. Contributions therefore start compounding from the following year — a deliberately conservative convention.
Is my salary information safe?
Yes. The whole projection runs client-side in your browser; no salary or balance data is transmitted anywhere.
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