401k Growth Projection Calculator
A 401k builds wealth through two engines: the contributions you and your employer add each year, and the compound growth that accumulates on the whole balance over time. This calculator projects your future 401k balance by growing your current balance at the assumed return and adding the future value of each year's combined contributions. Enter your current balance, your annual contribution, your employer match, an expected annual return, and the number of years to retirement, and the tool returns the projected balance and the total you will have contributed. The model uses end-of-year contributions and a fixed annual return, the standard textbook approach, so it is transparent and reproducible rather than a guess. All inputs are editable so you can test different savings rates, return assumptions and time horizons and see how powerfully small changes compound over decades. This is a projection, not a guarantee: real returns vary from year to year, and the IRS sets annual contribution limits that may cap what you can add. Use it to understand the trajectory of your savings and the impact of starting early. Every figure here is computed deterministically from the formula shown in full below, with a worked example that reconciles exactly to the calculator so you can follow each step.
A 401k projection grows the balance and the contributions: future value = balance times (1+r)^n plus the future value of yearly contributions. A $20,000 balance with $9,000 a year (contribution plus match) at 7% for 30 years projects to $1,002,392.18.
401k Growth Projection formula
FV = B x (1 + r)^n + C x [ ((1 + r)^n - 1) / r ]
B = current balance, C = annual contribution plus employer match
r = annual return as a decimal, n = number of years
The second term is the future value of an ordinary annuity
The current balance compounds on its own, while each year's combined contribution is grown to retirement and summed using the future-value-of-an-annuity factor.
Worked example
Project a 20,000 balance with 6,000 of annual contributions plus a 3,000 employer match (9,000 total) at 7% for 30 years.
- Growth factor: 1.07^30 = 7.612255
- Balance growth: 20,000 x 7.612255 = 152,245.10
- Annuity factor: (7.612255 - 1) / 0.07 = 94.460785
- Contributions grown: 9,000 x 94.460785 = 850,147.07
- Projected balance: 152,245.10 + 850,147.07 = 1,002,392.18
These are the calculator's default inputs, so the result above matches the widget exactly.
401k Growth Projection Calculator: frequently asked questions
How does 401k growth compound?
Each year your balance earns a return, and that return is added to the balance so it earns its own return the next year. New contributions join the pool and compound too, which is why starting early has an outsized effect.
Should I include the employer match?
Yes. An employer match is part of your total annual contribution and compounds just like your own. This calculator adds the match to your contribution before projecting growth, which is why it is a separate input.
What return should I assume?
Long-run returns vary by asset mix and are never guaranteed. Many people model a moderate figure such as 6% or 7% for a diversified portfolio, then test lower and higher rates to see the range of outcomes.
Are there contribution limits?
Yes. The IRS sets an annual elective deferral limit for 401k contributions, with a catch-up amount for those age 50 and over. Employer matches have separate combined limits. Check the current IRS figures.
What is the 401k growth formula?
Future value equals the current balance times (1 plus return) to the power of years, plus the combined annual contribution times the future-value-of-an-annuity factor. With the defaults, the projection is 1,002,392.18.
Official sources
- US retirement and benefits guidance: US Social Security Administration (SSA). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.