The gap between your salary and your actual take-home pay is one of the most jarring discoveries of adult life. You accept a job at $70,000 and then your first paycheck arrives and it is noticeably less than $70,000 divided by 24. Where did the rest go?
Understanding paycheck deductions is not optional financial knowledge. It determines what you can actually afford.
The anatomy of a paycheck
Your gross pay is divided by your pay periods. If you are paid biweekly (26 times per year), a $70,000 salary gives you $2,692.31 per pay period before any deductions. Then the subtractions begin.
Federal income tax is calculated based on your W-4 filing status and the tax bracket system. For a single filer in 2025 with no additional adjustments, biweekly federal withholding on $2,692 is approximately $306.
State income tax varies dramatically. California takes about 6-9.3% in most brackets. Texas takes 0%. New York City adds a city tax on top of the state tax. This single variable can mean a difference of $200+ per paycheck.
Social Security (FICA) takes 6.2% of your gross pay up to the annual wage base ($168,600 in 2025). On $2,692, that is $166.92.
Medicare takes 1.45% with no cap. On $2,692, that is $39.04. If you earn over $200,000, an additional 0.9% Medicare surtax kicks in.
Pre-tax deductions include your 401k contributions, health insurance premiums, HSA contributions, and FSA contributions. These reduce your taxable income, which is why they are called "pre-tax." If your health insurance premium is $150 per pay period and you contribute 6% to your 401k ($161.54), those $311.54 come off before taxes are calculated.
Running the numbers on $70,000
Here is a realistic breakdown for a single filer in a state with 5% income tax, biweekly pay, contributing 6% to 401k with $150 health insurance:
| Line item | Amount |
|---|---|
| Gross pay | $2,692.31 |
| 401k (6%) | -$161.54 |
| Health insurance | -$150.00 |
| Taxable gross | $2,380.77 |
| Federal tax | -$247.00 |
| State tax (5%) | -$119.04 |
| Social Security | -$166.92 |
| Medicare | -$39.04 |
| Net pay | $1,808.77 |
Your $70,000 salary becomes roughly $47,028 per year in take-home pay. That is 67.2% of your gross. The other 32.8% went to taxes, retirement, and insurance.
Why pay frequency matters
The same $70,000 salary produces different per-paycheck amounts depending on frequency:
- Weekly (52 pay periods): $1,346.15 gross
- Biweekly (26 pay periods): $2,692.31 gross
- Semi-monthly (24 pay periods): $2,916.67 gross
- Monthly (12 pay periods): $5,833.33 gross
Biweekly and semi-monthly are not the same thing, and this trips people up constantly. Biweekly means every two weeks (26 paychecks), semi-monthly means twice per month on fixed dates like the 1st and 15th (24 paychecks). Biweekly gives you two "extra" paychecks per year, which is why some months you get three paychecks instead of two.
W-4 adjustments that change everything
The W-4 form determines your federal withholding. If you are over-withheld (getting large tax refunds), you are essentially giving the government an interest-free loan. If you are under-withheld, you owe at tax time and might face penalties.
The key adjustments are on lines 3 and 4 of the W-4. Line 3 lets you claim tax credits (like the child tax credit) to reduce withholding. Line 4(a) adds other income, 4(b) claims deductions beyond the standard deduction, and 4(c) requests extra withholding.
Getting these right means your paychecks are larger throughout the year instead of waiting for a refund.
The tool that does the math
Every paycheck calculation involves interdependent variables: filing status, state, deductions, pre-tax contributions, pay frequency. Changing one affects the others. I built an ADP-style paycheck calculator that models all of these simultaneously so you can see exactly what your take-home pay will be before accepting a job offer or adjusting your deductions.
I'm Michael Lip. I build free developer tools at zovo.one. 500+ tools, all private, all free.
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