How this works
A US paycheck has more moving parts than the headline tax rate suggests. Five layers, all stacking on the same gross. **Pre-tax deductions** — 401(k) contributions and most health-insurance premiums — come off gross before any tax is calculated, lowering both federal taxable income and (for health, but not 401(k)) the FICA wage base. **Federal income tax** runs the 2024 IRS brackets after the standard deduction ($14,600 single / $29,200 joint). **FICA** is two pieces: 6.2 % Social Security on wages up to $168,600 (the SS wage base, indexed each year) and 1.45 % Medicare on every dollar of wages, plus an additional 0.9 % Medicare on wages above $200,000. **State income tax** is a wild card — zero in seven states (Texas, Florida, Washington, Nevada, South Dakota, Wyoming, Alaska), up to 13.3 % top marginal in California, with most states somewhere in 4 – 7 % flat-ish averages. The widget asks for a single flat rate; punch in your state's marginal or average depending on what you want to model.
The per-paycheck figure depends on how often you're paid. Biweekly (every two weeks, 26 paychecks/year) is the most common arrangement for salaried W-2 employees in the US. Semimonthly (twice a month, 24 paychecks/year) is the second most common. Monthly (12/year) is rarer but still seen, especially in government and academia. The calculator just divides the annual figure by 26 / 24 / 12 — in practice your employer's payroll may smooth slightly differently across the year (e.g. holding back the additional Medicare on a single paycheck rather than spreading it), so a single-paycheck reality may differ by a few dollars from this average.
What this doesn't model: 401(k) catch-up contributions for over-50s ($7,500 extra in 2024), HSA / FSA / dependent-care FSA pre-tax pulls, supplemental insurance, garnishments, local / city income taxes (NYC adds 3 – 4 %, San Francisco has additional payroll levies), Roth 401(k) vs. traditional 401(k) differences, and the special rules for employees whose primary residence is in a state different from their work state.
The formula
401(k) and health are subtracted pre-tax from federal taxable wages. Only health is subtracted from the FICA wage base — traditional 401(k) is fully FICA-taxable on the way in (and fully income-taxable on the way out at retirement; that's the trade-off). State tax modelled here is a single flat rate against federal-taxable wages — which works for the seven income-tax-free states and reasonably well for flat-tax states like Pennsylvania (3.07 %), Illinois (4.95 %), Indiana (3.15 %). Bracket-based states like California or New York will be approximate.
Example calculation
- Single, $75,000 salary, 6 % 401(k), $2,400/yr health, 5 % state, biweekly.
- Pre-tax: $4,500 401(k) + $2,400 health = $6,900. Fed-taxable wages $68,100, FICA wages $72,600.
- Fed tax ≈ $6,164, SS $4,501, Medicare $1,053, state $3,405. Net ≈ $53,477/yr ≈ $4,456/mo ≈ $2,057/biweekly. Effective rate 28.7 %.
Frequently asked questions
Why is my actual paycheck different from this number?
Three main reasons. (1) Withholding ≠ tax liability — your employer withholds based on your W-4 (filing status, dependents, additional withholding requests), not the actual tax owed. The annual reconciliation in April either refunds the over-withholding or charges the under. (2) Locality taxes — NYC, Philadelphia, San Francisco and several others add city or local income taxes the calculator doesn't model. (3) Smoothing — Social Security stops at the wage cap mid-year for high earners, so paychecks late in the year get bigger; the calculator divides evenly. For a real-life paycheck check the digits exactly on your pay stub against the deductions list shown here.
Should I max out my 401(k)?
Mathematically: contribute at least enough to capture your employer's full match — that's a 100 % instant return on the matched portion, with no equivalent elsewhere. Beyond the match, traditional 401(k) is a bet that your retirement marginal rate will be lower than your current marginal rate; for most workers in the 22 %+ bracket this holds, so maxing out makes sense if cash flow allows. Roth 401(k) (if your employer offers it) flips that — you pay tax now and withdraw tax-free, better if you expect rates to rise or your retirement income to be high. The 2024 employee limit is $23,000 ($30,500 with the over-50 catch-up). The widget treats the contribution as traditional — switch to Roth in the calculation by setting the 401(k) field to 0 and treating your contribution as part of take-home you choose to invest.
Does this handle bonuses correctly?
Only as part of your annual salary input. Federal tax on bonuses uses one of two methods at the employer's discretion: the percentage method (22 % flat federal withholding on supplemental wages up to $1M, 37 % above) or the aggregate method (lumped into your normal paycheck and withheld at your regular rate). The flat 22 % method often over-withholds for sub-$80k workers and under-withholds for higher earners; the aggregate method tracks better but is annoying for the payroll system. Either way, the annual reconciliation in April smooths it out — the calculator's annual figure is what you'd see across the full year, just paid in lumpy chunks throughout. For just-the-bonus estimation, treat the bonus as additional salary and re-run with a higher gross.