What percentage of my paycheck goes to taxes?

For most Americans earning $40K–$120K, total tax withholding is 25–35% of gross pay. This includes: federal income tax (12–22%), FICA (7.65% — 6.2% Social Security + 1.45% Medicare), and state income tax (0–13% depending on state). Pre-tax deductions like 401(k) reduce taxable income and lower your effective rate.

How does a 401(k) contribution affect take-home pay?

Contributing to a 401(k) reduces your taxable income, so federal and state taxes are calculated on a smaller amount. Example: $75,000 salary with 6% 401(k) = $4,500/yr contribution, but your taxable income drops to $70,500. At a 22% marginal rate, you save $990 in federal taxes. Your take-home pay only drops by ~$3,510 despite saving $4,500.