How We Calculate: Sources and Assumptions

Tax-year 2026 figures. Reviewed October 2026.

This page lists the numbers and assumptions behind each calculator, so you can check them against the original sources.

Sources

Federal income tax: 2026 brackets after the standard deduction ($16,100 single, $32,200 married filing jointly, $24,150 head of household), on pay after any pre-tax 401(k).
Social Security: 6.2% of wages up to $184,500. Medicare: 1.45% of all wages, plus 0.9% on wages above $200,000 (single or head of household) or $250,000 (married filing jointly).
State income tax: an approximate flat rate for the state you choose, applied to pay after pre-tax 401(k). States have different brackets and deductions, so this is an estimate. Enter your own rate for a closer figure. Local taxes and state payroll taxes (such as disability insurance) are not included.
Assumes one job, no tax credits, no extra W-4 withholding, and no pre-tax benefits other than a 401(k). Annual tax is divided across your paychecks, so it estimates your tax, not the exact amount a payroll system withholds.

Federal withholding at the flat 22% supplemental rate (37% on supplemental pay above $1 million in a year). Employers can also use the aggregate method, which gives a different amount.
Social Security, Medicare and additional Medicare are applied to the bonus on top of your salary, respecting the wage base and thresholds.
"Federal tax your bonus really adds" is the difference between the bracket tax on salary plus bonus and on salary alone, after the standard deduction.

2026 limits: $24,500 employee deferral, plus $8,000 catch-up at 50 and over, or $11,250 at ages 60 to 63. Pay counted for contributions is capped at $360,000.
Assumes a traditional (pre-tax) 401(k). Tax saved is the drop in federal bracket tax, plus your state estimate.
The projection adds contributions and match at the end of each year at a steady return, with no raises and no inflation adjustment.

Overtime: hours over your threshold (40 a week by default) paid at the multiplier you choose. State daily overtime rules are not modeled.
PTO: yearly PTO hours divided across pay periods, plus carry-over, minus hours used, limited by an optional cap.
FMLA: the three federal eligibility tests (12 months, 1,250 hours, 50 employees within 75 miles, or a public agency or school). It does not check whether your reason for leave qualifies.
Salary conversion: hourly pay = annual pay divided by hours per week times weeks per year.

We update the figures every year when new limits are published, and fix errors when we find them. Spotted something? Contact us.