How the estimate is built
Each line is one step from gross pay to take-home pay. Social Security and Medicare use the 2026 values from IRS Publication 15 [1]: 6.2% up to a $184,500.00 wage base, 1.45% with no limit, and 0.9% more on wages above $200,000.00. Income tax is the percent you enter, applied to your pay after pre-tax deductions.
Take-home = gross − pre-tax deductions − Social Security − Medicare − Additional Medicare − income tax − post-tax deductions
Social Security = 6.2% × the part of Social Security wages still below the wage base. Medicare = 1.45% × Medicare wages. Additional Medicare = 0.9% × the part of year-to-date Medicare wages above $200,000. Income tax = percent × (gross − all pre-tax deductions).
Amounts are shown to the cent. Nothing is rounded along the way, so a total can differ by a cent from the sum of the rounded lines. Not modelled: employer taxes, local taxes, garnishments, the employer’s 401(k) match and tax credits.
Example: a typical biweekly check
$78,000.00 a year, paid every two weeks, $100.00 in cafeteria-plan premiums, $150.00 to a 401(k), 10% federal and 4% state withholding, $25.00 post-tax.
- Gross: $78,000.00 ÷ 26 = $3,000.00
- Social Security and Medicare wages: $3,000.00 − $100.00 = $2,900.00 (the 401(k) does not reduce them)
- Social Security: 6.2% × $2,900.00 = $179.80; Medicare: 1.45% × $2,900.00 = $42.05
- Income-tax wages: $3,000.00 − $100.00 − $150.00 = $2,750.00; federal 10% = $275.00; state 4% = $110.00
- Deductions: $100.00 + $150.00 + $179.80 + $42.05 + $275.00 + $110.00 + $25.00 = $881.85
- Take-home: $3,000.00 − $881.85 = $2,118.15
Example: crossing the Social Security wage base
$260,000.00 a year paid every two weeks ($10,000.00 a check), with $180,000.00 already earned this year.
- Room left under the wage base: $184,500.00 − $180,000.00 = $4,500.00
- Social Security: 6.2% × $4,500.00 = $279.00; the other $5,500.00 of this check pays none
- Medicare: 1.45% × $10,000.00 = $145.00
Example: crossing $200,000
The same check with $195,000.00 earned so far. The wage base is already behind it, so Social Security is $0.00.
- Medicare: 1.45% × $10,000.00 = $145.00
- Year-to-date after this check: $195,000.00 + $10,000.00 = $205,000.00, which is $5,000.00 over $200,000.00
- Additional Medicare Tax: 0.9% × $5,000.00 = $45.00
Questions
What are Social Security and Medicare tax?
For 2026 the employee share is 6.2% for Social Security and 1.45% for Medicare [1]. Together they are often called FICA. Your employer pays a matching share on top, which is not taken from your pay.
What is the Social Security wage base?
What is Additional Medicare Tax?
Which pre-tax deductions reduce Social Security and Medicare wages?
It depends on the kind. The IRS says benefits under a cafeteria plan (such as many health premiums) may be excluded from Social Security and Medicare wages, while 401(k) deferrals are exempt from income tax withholding but still taxable for Social Security and Medicare [1]. That is why there are two pre-tax boxes. Ask your payroll department which applies to each deduction.
Why do I enter income tax as a percent?
Federal withholding depends on your Form W-4, your filing status, how often you are paid and tax tables that change, and state and local rules differ. Rather than guess, the calculator uses the percent you give it. The IRS Tax Withholding Estimator is the tool for working out the right amount [3]. A rough percent is the federal withholding on a recent pay stub divided by that stub’s taxable wages.
Why will my real paycheck differ?
Payroll systems round each line to the cent, may include taxes or deductions not modelled here (local taxes, garnishments, employer-specific items) and may withhold on bonuses differently. Treat the result as an estimate and rely on your pay stub.