401k Calculator: See How Much Your 401(k) Will Grow
This 401k calculator projects how much your 401(k) will be worth when you retire. Enter your current balance, monthly contributions, expected return, and the years until retirement. The calculator above then shows your savings at retirement and how much comes from growth versus your own deposits. Use it to test how small changes today shape your future nest egg.
How it's calculated
The 401k calculator grows your current balance and monthly contributions forward to your retirement age. It assumes a fixed annual return that compounds each year. You enter your starting balance, monthly contribution (including any employer match), expected yearly return, and target retirement age.
The tool then splits your final balance into two parts: the money you put in and the investment growth on top. This split reveals the power of compounding. Real markets rise and fall, so treat the result as a planning estimate, not a guarantee. To plan beyond your workplace plan, see the retirement savings calculator.
A worked example
Say you are 30 years old with $20,000 already in your 401(k). You contribute $800 per month, including your employer match, and expect a 7% annual return until you retire at 65. The calculator projects $1,540,606 in savings at retirement. Your $20,000 starting balance plus $336,000 in contributions over 35 years make up the money you put in, while investment growth adds $1,184,606. Using the 4% rule, that balance could provide about $5,135 per month in your first year of retirement.
Common mistakes to avoid
- Skipping the full employer match. The match is free money and an instant return on your contribution. Always contribute enough to capture every matching dollar your employer offers.
- Forgetting to include the employer match in your monthly contribution figure. The calculator expects your total monthly deposit, so add your share plus your employer's.
- Setting an unrealistic return rate. A fixed 7% is a common long-term stock estimate, but higher numbers can badly overstate your balance.
- Waiting too long to start. Starting at 30 instead of 40 gives your money an extra decade to compound, which often doubles the final result.
- Ignoring the 2026 contribution limit. You can defer up to $24,500 in 2026, plus an $8,000 catch-up if you are age 50 or older.
Frequently asked questions
What does a 401k calculator do?
A 401k calculator projects how much your 401(k) will grow by retirement. You enter your balance, monthly contributions, expected return, and retirement age. It then estimates your final savings and shows how much comes from growth versus your own deposits.
How much can I contribute to a 401(k) in 2026?
You can contribute up to $24,500 to your 401(k) in 2026. If you are age 50 or older, you can add an $8,000 catch-up contribution, for a total of $32,500. These limits apply to your own deferrals, not employer matching.
Does the calculator include my employer match?
Yes, if you include the match in your monthly contribution. Enter your total monthly deposit, combining your own contribution and your employer's match. The employer match is essentially free money, so contribute enough to earn the full amount offered.
How much does an employer match add over a career?
The impact is substantial. On a $50,000 salary with a 3% employer match, your employer contributes $1,500 per year. At a 7% annual return over 30 years, that $1,500 annual match alone grows to approximately $141,700 — without you contributing a single extra dollar. The match is also an instant 100% return on the dollars that trigger it, which is why always contributing enough to capture the full match is the highest-priority step in retirement planning. To model the combined effect of your contributions and the match, include both amounts in the monthly contribution field above, then compare the full projection in the retirement savings calculator.
What return rate should I use?
Many planners use a fixed 7% annual return as a long-term stock market estimate. The calculator assumes this rate stays the same every year. Real returns vary, so treat the projection as an estimate and try a few different rates.
What if I withdraw from my 401(k) early?
Withdrawing before age 59½ usually costs a 10% penalty plus income tax, and it erases future growth. Estimate the damage first with our 401k early withdrawal calculator before cashing out.