401(k) Calculator
This 401(k) calculator projects how large your workplace retirement account could grow by the time you retire, combining your own salary-deferral contributions, your employer match, and compounding investment returns. It models contributions monthly and grows your existing balance plus every new dollar at your expected rate, so you can see the split between what you put in, what your employer adds, and what market growth contributes. Adjusting the contribution percentage or match limit instantly reveals how much each lever changes the final nest egg.
Formula
FV = B·(1+i)^N + (C+E)·((1+i)^N − 1) / i
- B
- Current 401(k) balance
- C
- Monthly employee contribution = salary × contribution% ÷ 12
- E
- Monthly employer match = salary × min(contribution%, limit%) × match% ÷ 12
- i
- Monthly return = annual return ÷ 12 ÷ 100
- N
- Number of months = (retirement age − current age) × 12
How it works
- Enter your current age and planned retirement age; the difference sets the number of years your money compounds. Add your annual salary and the percentage of it you contribute to the plan.
- Set the employer match: the match percentage (e.g. 50%) and the match limit (the maximum share of salary the employer will match). The tool matches the smaller of your contribution rate and that limit.
- Choose an expected annual return. Contributions are spread across 12 months and grown at the monthly rate, and the result card breaks the balance at retirement into your contributions, employer contributions, and investment growth.
Worked example
Age 30 retiring at 65, $80,000 salary, contributing 10%, employer matches 50% up to 6% of salary, 7% expected return, $20,000 starting balance.
- Years to retirement = 65 − 30 = 35, so N = 420 months; monthly rate i = 7 ÷ 12 ÷ 100 ≈ 0.005833.
- Annual employee contribution = 80,000 × 10% = $8,000 → $666.67/mo. Matchable rate = min(10%, 6%) = 6%, so employer adds 80,000 × 6% × 50% = $2,400/yr → $200/mo.
- Grow the $20,000 balance and the combined $866.67 monthly deposits at 0.5833%/mo for 420 months.
Balance at retirement ≈ $1,791,037, made up of $280,000 of your contributions, $84,000 of employer match, and about $1,407,037 of investment growth.
Frequently asked questions
- How does the employer match limit work here?
- The match applies only to the portion of your salary up to the limit. If you contribute 10% but the employer matches 50% only up to 6%, the match is calculated on 6% of salary, not 10%, because that is the lower of your rate and the cap.
- Does this calculator apply IRS contribution limits?
- No. It uses the contribution percentage you enter without capping it at the annual IRS elective-deferral limit. If your percentage times your salary exceeds the legal limit, reduce the percentage so the projection stays realistic.
- Is the investment growth figure guaranteed?
- No. The expected return is a fixed assumption applied every month, but real 401(k) returns vary year to year and can be negative. Treat the projection as a planning estimate, not a promise of future value.
- Are taxes and fees included in the result?
- No. The balance shown is pre-tax for a traditional 401(k) and ignores fund expense ratios and administrative fees. Withdrawals in retirement are taxed as ordinary income, which this tool does not deduct.