THE NUMORIX GUIDE
How to use the Paycheck Calculator (Detailed)
Last reviewed September 14, 2026
What this calculator does
The detailed engine treats salary as annual, divides it by 52, 26, 24, or 12 for the selected frequency, and calculates annual federal tax from separate simplified single or married brackets.
Formula and method
The detailed engine treats salary as annual, divides it by 52, 26, 24, or 12 for the selected frequency, and calculates annual federal tax from separate simplified single or married brackets. It adds salary x entered stateTaxRate, Social Security capped at $168,600, and Medicare at 1.45%, then divides the annual deductions by the pay-period count before subtracting them from gross pay.
Variables and inputs
Enter annual salary, weekly/biweekly/semimonthly/monthly frequency, single or married filing status, and a state tax rate percent. The UI also stores a CA state label, but it does not render that field and the engine's state argument is not used in the calculation.
Worked example
With $75,000 annual salary, biweekly pay, single filing, and a 9.3% entered state rate, gross pay is $2,884.62. The engine returns about $444.37 federal, $268.27 state, $178.85 Social Security, and $41.83 Medicare per period, leaving net pay of about $1,951.31 and an effective rate displayed as 32.4%.
How to interpret the result
The breakdown makes the route's annual-tax-to-pay-period conversion visible. Filing status changes the hardcoded federal bracket path, while the state rate is a direct user input; neither result represents an employer's exact withholding table.
Common mistakes to avoid
Enter annual salary rather than a single paycheck amount. Use `semimonthly` as the route's frequency concept rather than assuming 24 monthly checks means the same dates as biweekly pay. Enter 9.3 for 9.3%, not 0.093.
Assumptions and limitations
The 2025 federal brackets are simplified and the model omits standard deductions, credits, local taxes, additional Medicare tax, benefits, retirement, garnishments, bonuses, and withholding-form elections. The state name argument is ignored, and a zero or invalid frequency falls back to 26 periods in the engine.