How we calculate

Paycheck calculators

1. Gross pay

Salary mode divides annual salary by the number of pay periods (52 weekly, 26 bi-weekly, 24 semi-monthly, 12 monthly). Hourly mode multiplies rate × regular hours, adds overtime hours at 1.5× the rate, and annualises at 52 weeks.

2. Pre-tax deductions

Traditional 401(k) and 403(b) contributions reduce wages subject to federal income tax and, in every state except Pennsylvania and New Jersey, state income tax. They do not reduce Social Security or Medicare wages. Section 125 items (employer health premiums, HSA and FSA contributions) reduce federal, state and FICA wages.

3. Federal income tax withholding

We implement Worksheet 1A of IRS Publication 15-T (2026), the percentage method for automated payroll systems, for a Form W-4 from 2020 or later:

adjusted annual wage = annual taxable wages + W-4 4(a) other income
                      − W-4 4(b) deductions − (Step 2 box checked ? 0 : $8,600, or $12,900 if married filing jointly)
tentative withholding = STANDARD or STEP-2-CHECKBOX schedule applied to the adjusted annual wage
annual withholding    = max(0, tentative − W-4 Step 3 credits)
per-paycheck          = annual withholding ÷ pay periods + W-4 4(c) extra withholding

The published schedules equal the ordinary 2026 brackets shifted by the standard deduction ($16,100 single, $32,200 joint, $24,150 head of household) less the built-in amount above; the checkbox schedule halves the bracket widths. Our test suite checks the engine against the first rows of every published 2026 table (for example $0–$7,500 at 0%, then 10% to $19,900 and 12% to $57,900 for single filers). Married filing separately uses the single schedule for withholding, exactly as the IRS tables do.

4. Social Security and Medicare (FICA)

Social Security = 6.2% × min(FICA wages, $184,500)
Medicare        = 1.45% × FICA wages + 0.9% × max(0, FICA wages − $200,000)

The 2026 wage base is $184,500 (SSA). Because the calculator assumes even pay through the year, it caps Social Security per period at the wage base divided by pay periods; a real payroll stops withholding once your year-to-date wages pass the base. The 0.9% Additional Medicare Tax is withheld above $200,000 regardless of filing status (IRS Topic 751).

5. State income tax

State tax is an annualised estimate, not a reproduction of each state's employer withholding tables:

state taxable income = annual state wages − standard deduction − personal exemptions (self, spouse if joint, dependents)
state tax            = bracket schedule(state taxable income) − any deduction or exemption credits

Rates, brackets, standard deductions and exemptions for all 50 states and DC come from the Tax Foundation's State Individual Income Tax Rates and Brackets, 2026 (as of January 1, 2026), cross-referenced to each state revenue department's withholding page linked on the state's calculator. Married filing separately and head of household use the single schedule. Simplifications are stated on each state page: for example, Alabama's and Oregon's deduction for federal tax paid, Connecticut's and New York's benefit recapture, and Arkansas's low-income table are not modeled. Utah's taxpayer credit and Kentucky's non-doubled standard deduction are.

6. Local income tax

Where a state has local income taxes, the calculator offers a rate field. Maryland and Indiana require one (every county levies a tax); New York, Ohio, Pennsylvania, Michigan, Kentucky, Missouri, Alabama, Delaware, Oregon and Colorado offer it as optional. The rate is applied to state wages (after Section 125 items); actual local bases vary.

7. State payroll programs

Employee-paid programs are included as separate lines where the 2026 rate is verified: California, Colorado, Connecticut, Massachusetts, New Jersey, New York, Oregon, Rhode Island, Washington. Each line's rate, wage base and source are in the state's data file and listed under Sources on its page. Programs whose 2026 rate we could not verify are named on the page but not deducted.

8. Rounding

All math is done in floating-point dollars and rounded to the cent only for display. Employers round differently (some to the dollar per period), so expect small differences.

Tax-year calculators

The federal income tax calculators estimate the tax on Form 1040 for ordinary income:

taxable income = income − pre-tax contributions − max(standard deduction, itemized deductions)
tax before credits = bracket schedule(taxable income)
Child Tax Credit   = $2,200 per qualifying child + $500 per other dependent,
                     reduced by $50 per $1,000 of income above $200,000 ($400,000 joint)
income tax         = max(0, tax before credits − Child Tax Credit)

Long-term capital gains rates, the alternative minimum tax, refundable credits and above-the-line deductions other than the ones you enter are out of scope, and the page says so.

Money calculators

Each finance calculator states its formula on its own page. Compound growth uses the standard future-value formulas with the compounding frequency you pick; loan payments use the amortisation formula; payoff calculators simulate month by month so extra payments are handled exactly. None of them apply tax unless the page says so.

What we do not do

• We do not store what you type. Calculations run in your browser; nothing is sent to a server.
• We do not give tax advice. The numbers are estimates for planning; your payroll department, tax software or a professional has the final word.
• We do not silently change numbers. Every data file carries the date it was verified and the sources used, and the date appears at the bottom of each page.

Update schedule

Federal figures are updated when the IRS publishes the next year's Revenue Procedure (usually October) and Publication 15-T (December). State figures are refreshed in January and whenever a state enacts a mid-year change. The current data set was verified on September 3, 2026.