How it works
How the 401(k) projection works
Each year your salary grows, your contribution and employer match are added month by month, and the whole balance compounds at your expected return until you retire.
Assumptions and formulas
Employee contribution = salary × contribution % (capped at the 2026 limit for your age that year)Employer match = match rate × the smaller of (your contribution, match cap % × salary)Monthly rate = (1 + annual return)^(1/12) − 1; each month: balance = balance × (1 + monthly rate) + (employee + employer) ÷ 12Balance in today's dollars = nominal balance ÷ (1 + inflation)^yearsConvention: contributions are made evenly each month at month end, salary increases once a year, and the annual limit is checked each year using your age that year. The age-60-to-63 "super catch-up" of $11,250 replaces the regular $8,000 catch-up. Limits are held at 2026 values for all future years, although the IRS normally raises them with inflation, so the projection is conservative on that point.
2026 limits used: employee deferral $24,500; catch-up $8,000 (age 50+); $11,250 (ages 60 to 63); plan compensation cap $360,000; total employee plus employer limit $72,000 (employer money is trimmed if the total would exceed it).
Tax treatment: traditional 401(k) contributions are made before income tax and grow tax-deferred, so you owe ordinary income tax on withdrawals. Roth 401(k) contributions are made after tax and qualified withdrawals are tax-free. This calculator shows the pre-tax balance; it does not subtract the tax you will owe on withdrawals, fees, or required minimum distributions.
Returns are not guaranteed. Past stock-market averages are not a forecast; try several return rates, for example 4%, 6% and 8%.