401(k) Calculator (US)

What is a 401(k)?

A 401(k) is a US employer-sponsored retirement account. You contribute pre-tax dollars (Traditional) or after-tax (Roth), reducing your current tax burden, and the money grows tax-deferred until withdrawal.

Always capture the full employer match

If your employer matches 50% of your contribution up to 6% of salary, contribute at least 6% — that match is literally free money (a 50% instant return). Failing to capture it is one of the most common financial mistakes.

2025 contribution limits

• $23,000 standard limit (under 50)
• +$7,500 catch-up if 50 or older
• $69,000 total combined (employee + employer) limit

Roth vs Traditional

This calculator estimates raw account growth without distinguishing Roth/Traditional. For after-tax purposes: Traditional is taxed at withdrawal at your future bracket; Roth is paid up-front so the future balance is tax-free.

Important caveats

• Returns are nominal — subtract ~3% for real (inflation-adjusted) returns
• Doesn't model fees, which compound just like returns (negatively)
• Contribution limit may bind: cap your contribution % so total stays under $23k