401(k) Contribution Impact Calculator
See how changing your 401(k) contribution affects take-home pay and projected retirement balance.
Includes employer match and 20-year growth view.
How 401(k) Contributions Work A 401(k) is a pre-tax retirement account offered by employers. Contributions reduce your taxable income, so you pay less in federal income tax today. Your money then grows tax-deferred until retirement.
The Tax Advantage If you earn $75,000 and contribute 10% ($7,500), your taxable income becomes $67,500. At a 22% marginal rate, you save $1,650 in federal taxes. Your take-home only drops by $7,500 - $1,650 = $5,850, not the full $7,500.
Employer Match — Free Money If your employer matches 50% of your contributions up to 6% of salary:
- Contribute 6% ($4,500) → employer adds $2,250 per year
- That is a 50% instant return on your contribution
- Always contribute at least enough to capture the full employer match
Future Value Formula (Annual Contributions) FV = Annual Contribution × ((1 + r)^n - 1) / r Where r = annual return rate, n = years to retirement
2024 Contribution Limits Employee limit: $23,000 ($30,500 if age 50+) Total combined limit (with employer match): $69,000
Key Insight Starting at 25 vs. 35 with the same monthly contribution typically results in more than double the final balance — due to compound growth over 10 extra years.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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