Payroll Tax Withholding (Simplified)
Federal income tax (Pub 15-T percentage method), employee FICA, Additional Medicare.
Example
You enter
- Gross wages this period (USD) 1500
- Pay frequency biweekly
- Filing status single
- Tax year 2025
You get
- Annual gross 39000
- Federal income tax this period $101.60
- Fed income tax annual 2641.5
- Social Security this period $93
- Medicare this period $21.75
- Total employee deduction $216.35
Checked against published worked examples from: IRS Pub 15-T percentage method (single, biweekly, 2025).
Details, formula, and sources
ScopeSingle-filer brackets bundled.
Formula or tableAnnualize gross. Apply Pub 15-T percentage-method bracket: fed_annual = base + (annual_gross - prev) * rate. Divide by pay periods. FICA: SS = min(gross, wage_base - ytd) * 0.062. Medicare = gross * 0.0145. Additional Medicare = 0.9% above the threshold.
Source and editionIRS Publication 15-T, 2024, 2025 and 2026 Worksheet 1A standard schedules bundled (selected by tax year; other years read 2025). Single-filer only.
Free accessFree at irs.gov/publications/p15t.
What governsEstimate only. Tax law changes. Confirm with the current IRS publication or a licensed CPA before filing.
API field namesgross_per_period, pay_frequency, filing_status, tax_year, annual_gross, fed_income_tax_period, fed_income_tax_annual, ss_tax_period, medicare_period, total_employee_period
- Filer type single, 2020-or-later Form W-4 with no Step 2-4 entriesPub 15-T Worksheet 1A
- Standard deduction line 1g $8,600 folded into the bracket starts ($6,400 + $8,600 = $15,000 for 2025)Pub 15-T 2025 Worksheet 1A