401k Calculator
Estimate your 401k balance at retirement.
Input
Result
What is a 401k Calculator?
A 401k Calculator projects how much your retirement savings could grow over time. Enter your current balance, monthly contributions, expected annual return, and years until retirement to see your estimated future balance.
How to calculate 401k growth manually (the formula)
The future value of a 401k with regular contributions is calculated using the compound interest formula: FV = PV × (1 + r)t + PMT × [ (1 + r)t – 1 ] / r where PV is the current balance, PMT is the annual contribution, r is the annual return rate, and t is the number of years until retirement.
Example calculation
If you are 30 with $25,000 saved, contribute $500 per month ($6,000 per year), and earn a 7% annual return: after 35 years you would have about $1,127,000. You would have contributed $210,000 of your own money, and the remaining $917,000 would be investment growth.
Common mistakes
- Not contributing enough to get the full employer match — The employer match is free money. If your employer matches 50% up to 6%, contribute at least 6% to get the full match.
- Being too conservative or too aggressive — Young investors can afford more risk with higher potential returns. Near retirement, shift to more conservative allocations to protect savings.
- Cashing out when changing jobs — Cashing out triggers taxes and penalties. Rollover your 401k to an IRA or your new employer's plan instead.
- Ignoring fees — High expense ratios eat into returns over time. Even a 1% fee difference can cost tens of thousands over decades.
- Not increasing contributions over time — As your income grows, increase your contribution percentage. Many plans offer automatic annual escalation.
Frequently asked questions
How does a 401k calculator work?
A 401k calculator projects your retirement savings by taking your current balance, monthly contributions, expected annual return, and years until retirement. It uses compound growth math to estimate your future balance.
How much should I contribute to my 401k?
A common rule of thumb is to contribute at least enough to get the full employer match, which is free money. Many financial advisors suggest saving 10–15% of your income including the employer match.
What is a good annual return for a 401k?
Historically, the S&P 500 has averaged about 7–10% annual returns before inflation. A conservative estimate for planning purposes is 5–7% after inflation and fees.
When can I withdraw from my 401k without penalty?
You can withdraw penalty-free starting at age 59½. Withdrawals before that age typically incur a 10% early withdrawal penalty plus income tax on the amount withdrawn.
Is this calculator free to use?
Yes, completely free with no sign-up required. Use it as many times as you like.