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Formula & explanation
401K Calculator uses the following calculation:
This is a simplified model intended for planning and education. Real-world offers from lenders, institutions, or tax authorities may include additional fees, rules, or adjustments not reflected here.
Frequently asked questions
How much employer match am I leaving on the table?
If you contribute less than your plan's match cap, you're forfeiting free money — try to contribute at least enough to capture the full match.
What's the 2025 IRS 401(k) contribution limit?
Employee contributions are capped by the IRS each year (check current limits); employer contributions are separate and don't count against your personal cap.
Should I choose traditional or Roth 401(k)?
Traditional contributions reduce taxable income now with tax due at withdrawal; Roth contributions are taxed now but grow tax-free — the better choice depends on your expected tax rate in retirement.