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401k Contribution Calculator

This free 401k contribution calculator shows what a 401k contribution really costs you each paycheck. Enter your salary, contribution percentage, employer match, pay frequency, and tax rate, and it works out the amount taken from each paycheck, the match your employer adds, your total annual contribution, and — most importantly — how much your take-home pay actually drops once the tax saving is counted. It is about the paycheck impact, not the retirement balance: for a projection of what your account could grow to, see the 401k calculator.

How it works

A 401k contribution calculator answers a different question from a 401k balance calculator. A balance calculator projects what your account could be worth at retirement; this one shows what a contribution costs you right now, paycheck by paycheck. That matters because the number on your pay stub is not the number that leaves your pocket: pre-tax 401k contributions lower your taxable income, so part of every contribution comes back to you as tax saved.

Start with your annual salary and the percentage you contribute. A 6% contribution on a $75,000 salary is $4,500 a year. Divide that by the number of paychecks — 26 if you are paid biweekly, 52 weekly, 12 monthly — and you get the contribution taken out of each paycheck. That is the gross amount going into your 401k, before any tax effect.

Next comes the employer match. Many employers match a percentage of what you put in, up to a cap expressed as a percentage of your salary. A 50% match means the employer adds 50 cents for every dollar you contribute, and a 3% cap means the match stops at 3% of your salary. In the example above, 50% of $4,500 is $2,250, and 3% of $75,000 is also $2,250, so the full match is paid. If your contribution were larger, the cap would limit the match instead. The match is free money: it costs you nothing and goes straight into your account.

Finally, the tax saving. Traditional 401k contributions are pre-tax, so they reduce the income your federal tax is calculated on. If your marginal tax rate is 22%, every $100 you contribute saves $22 in tax, so your take-home pay only falls by $78. That is why raising your contribution often feels smaller than the number suggests. Note that this calculator uses only the federal marginal rate you enter; state tax, Social Security, and Medicare are not included, so treat the take-home figure as an estimate.

Two rules of thumb are worth keeping in mind. First, contribute at least enough to get the full employer match — turning down matched money is turning down a guaranteed, immediate return. Second, a common target is 15% of pay in total, counting your contribution plus the match, though the right number depends on your age, your other savings, and when you want to retire. Use the calculator to test a higher percentage and see the real paycheck cost before you change your election.

Worked example

Alex earns $75,000 a year, contributes 6% of salary, is paid biweekly, gets a 50% employer match capped at 3% of salary, and is in the 22% marginal tax bracket.

Step 1: Annual contribution — $75,000 × 6% = $4,500 per year.
Step 2: Per-paycheck contribution — $4,500 ÷ 26 = $173.08 per paycheck.
Step 3: Employer match — 50% × $4,500 = $2,250; the cap is 3% × $75,000 = $2,250, so the full $2,250 match is paid.
Step 4: Total annual contribution — $4,500 + $2,250 = $6,750 per year.
Step 5: Tax saved per paycheck — $173.08 × 22% = $38.08.
Step 6: Take-home reduction — $173.08 − $38.08 = $135.00 per paycheck.

Alex puts $173.08 per paycheck into the 401k, but take-home pay only drops by $135.00, while $6,750 a year in total goes into the account. Enter the same numbers in the calculator above and you will get exactly the same result.

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