Payroll Tax Calculator

Social Security (6.2%) and Medicare (1.45%) are flat statutory rates set by federal law and published by the IRS (Tax Topic 751) that apply the same way to every employee's wages (subject to the Social Security wage base, which this calculator does not model), so they're hardcoded. Federal and state income tax withholding, on the other hand, depends on filing status, allowances, deductions, and each state's own bracket structure, so there's no single correct rate to hardcode -- you enter your own effective rate instead.

No. Social Security tax only applies up to an annual wage base limit set each year, and by law it stops being withheld once your year-to-date earnings cross that threshold. This calculator applies the flat 6.2% rate to whatever gross pay figure you enter with no cap, so for very high pay periods or high annual earners past the wage base, its Social Security estimate will run higher than what actually gets withheld later in the year.

The Additional Medicare Tax is an extra 0.9% withheld on wages above a threshold for high earners, on top of the standard 1.45% Medicare rate. This calculator only applies the flat 1.45% rate regardless of income level, so it does not add that surtax -- for high earners above the threshold, actual Medicare withholding will be somewhat higher than this calculator's Medicare figure.

Since federal tax is a direct percentage of gross pay, each additional percentage point of federal rate reduces Net Pay by exactly 1% of Gross Pay. At this calculator's $5,000 default Gross Pay, moving the Federal Tax Rate up by 3 points (for example from 22% to 25%) reduces Net Pay by $150 for that pay period -- Federal Tax and Total Taxes both rise by that same $150, since Federal Tax is the output driving the change. State Tax, Social Security, and Medicare are unaffected, since none of them depend on the federal rate.