401(k) Calculator

What is 401(k) calculator?

A 401(k) calculator projects how a workplace 401(k) retirement account grows over time. A 401(k) lets you contribute pre-tax dollars straight from your paycheck, often with an employer match that is effectively free money (a common match is 50% of contributions up to 6% of pay), and the balance compounds tax-deferred until withdrawal in retirement. This calculator applies the standard compound-growth formula to your starting balance, monthly contribution, assumed return, and years to grow, so you can see the long-term payoff of starting early and contributing consistently. Use it to estimate whether you are on track, to see how maxing out contributions versus the minimum changes the final balance, or to model the impact of an employer match. Run the same inputs at 5%, 7%, and 9% to bracket conservative versus optimistic markets, and try 20 versus 30 years to see how time in the market dominates timing. The numbers run in your browser.

How to use this calculator

1. Enter your initial investment.
2. Enter your monthly contribution.
3. Enter your estimated annual return.
4. Enter your years to grow.
5. Click the "Calculate" button.
6. View your result instantly — the main result is displayed prominently at the top with a detailed breakdown below it.

When to use this calculator

• Projecting decades of 401(k) tax-deferred growth before retirement
• Estimating how an employer match lifts the final balance
• Comparing maxing out contributions versus a default 6% deferral
• Bracketing conservative 5% versus optimistic 9% return scenarios
• Seeing how starting 10 years earlier changes the ending balance