How much will your 401(k) be worth?
Modest contributions today can compound into a surprisingly large nest egg over a career. Here's what actually drives the final number — and why when you start matters more than almost anything else.
Reviewed by Robert · Updated June 2026
The three ingredients
- Your contributions — what you put in each month, ideally a steady percentage of your salary.
- Your employer's match — many employers match a portion of your contributions (e.g., 50% up to 6% of salary). This is effectively free money.
- Time and compound growth — your balance earns returns, and those returns earn returns. Over decades, this is the heavy lifter.
Don't leave the match on the table
If your employer matches contributions, contribute at least enough to capture the full match. A 50% match is an instant 50% return on that money — better than virtually any investment. Skipping it is leaving guaranteed money behind.
Why starting early wins
Because of compounding, a large share of your eventual balance comes from growth, not contributions — and growth needs time. A dollar invested in your 20s has decades to multiply; the same dollar invested in your 40s has far fewer. Starting even a few years earlier, or delaying a few years, can swing the final number dramatically.
Turning a nest egg into income: the 4% rule
A common rule of thumb estimates you can withdraw about 4% of your balance in the first year of retirement (adjusting for inflation thereafter) with a reasonable chance of not running out. So a $1,000,000 balance suggests roughly $40,000 of first-year income. It's a starting point, not a guarantee — actual outcomes depend on markets, spending, and longevity.
CapitalCalcs provides educational estimates, not financial advice. Investment returns vary and are not guaranteed. See how we calculate for the formulas and assumptions behind these tools.