401(k) retirement calculator
Project how much you could have at retirement with a monthly contribution, annual return and the years you have left.
Your inputs are processed in your browserProjection details
The simulation assumes contributions at the end of each month and monthly compounding.
Savings projection
Growth on contributions
Annual breakdown
| Year | Contributions | Growth | Ending balance |
|---|
How the projection works
The calculator adds your contribution at the end of each month and applies the monthly return to the accumulated balance. This lets you see how much comes from your own savings and how much comes from simulated investment growth.
The formula uses an annuity with monthly contributions: ending balance = monthly contribution × (((1 + r)^n − 1) / r), where r is the monthly return and n is the number of months. At 0% return, the result is simply all contributions.
What the result means
Total contributed adds every monthly contribution. Investment growth is the estimated part produced by the assumed return. The annual breakdown shows how the balance changes over time.
Try different contribution, return and term scenarios to compare the effect of starting earlier or saving more each month.
Assumptions and source
This page models a 401(k)-style account with a zero starting balance, contributions at the end of each month and a constant return. It does not calculate legal limits, employer matching, taxes, fees or inflation.
For current plan rules, see the IRS information about 401(k) plans. Reviewed on August 5, 2026.
Frequently asked questions
What does this 401(k) retirement calculator calculate?
It projects how much you could have at retirement from your monthly contribution, assumed annual return and years until retirement.
What annual return should I enter?
Enter an average rate you want to use as an assumption, such as 7%. It is not a guarantee of future returns.
Does it include taxes or employer contributions?
No. It only simulates your monthly contributions and a constant return; it does not include taxes, fees, inflation or employer contributions.
Are my details sent to a server?
The calculation runs in your browser, and the details you enter are not sent to the tool's server.