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Payroll Tax Calculator 2026: Federal, State, and FICA Rates Explained

What every payroll tax calculator has to get right in 2026: federal brackets, Social Security and Medicare rates, and state withholding basics.

7 min readUpdated 2026-09-22
Calculator resting on a stack of tax forms and financial documents

A payroll tax calculator turns gross pay into net pay by applying every withholding an employer is required to take out of a paycheck. The federal side is set once a year by the IRS; the state side varies enormously. A calculator that gets either wrong shows up in a mismatched Form 941 and, eventually, a notice.

This guide explains what the calculator is doing under the hood so you can sanity-check any tool you use, including the one built into Swift Paybooks.

FICA: Social Security and Medicare

FICA is the flat-rate side of payroll tax. Every employee pays 6.2 percent for Social Security and 1.45 percent for Medicare, matched dollar for dollar by the employer, for a combined 15.3 percent split evenly. Social Security stops at the annual wage base; Medicare does not.

High earners pay an additional 0.9 percent Medicare surtax on wages above the IRS threshold, withheld from the employee side only.

Federal Income Tax Withholding

Federal income tax withholding is not a flat rate. It is calculated from the employee's W-4 (filing status, dependents, other income, deductions, extra withholding) applied against the IRS Percentage Method tables for the year.

The 2020 W-4 redesign removed allowances entirely; a calculator that still asks for "number of allowances" is running on an out-of-date model. A correct calculator asks for filing status, whether the employee checked the multiple-jobs box, and any dollar amounts from steps 3 and 4 of the W-4.

State Income Tax Withholding

State withholding varies from "none" to "complex progressive with local surcharges". A calculator has to know:

  • The state (or states) the employee is working in
  • The state (or states) the employee is a resident of
  • The state's current withholding tables and standard deduction
  • Any local taxes that piggyback on state withholding (New York City, Ohio municipal taxes, and others)

State Unemployment Insurance (SUI)

SUI is an employer-side tax paid on a state-set wage base at a rate the state assigns based on your history. New employers get a "new employer rate" for the first few years; established employers get an "experience rate" that reflects past claims.

A calculator that treats SUI as a fixed rate for every business will be wrong for anyone who has been in business more than a couple of years.

Federal Unemployment (FUTA)

FUTA is 6.0 percent on the first $7,000 of every employee's wages, reduced to 0.6 percent for employers who pay their state unemployment on time. Miss a state deposit and the reduction can be clawed back, at which point the effective FUTA rate multiplies.

What to Sanity Check on Any Calculator

A quick way to sanity check any payroll tax calculator: run a $10,000 monthly gross-pay scenario for a single filer in a state with income tax, and read what falls out. Social Security should be $620. Medicare should be $145. Federal withholding should sit in the low four figures for a standard single filer with no adjustments. If any of those are off, the calculator is not applying the 2026 tables correctly.

Key Takeaways

  • FICA is 15.3 percent total, split evenly between employee and employer, with Social Security capped at the annual wage base.
  • Federal income tax withholding is driven by the redesigned W-4, not by allowances.
  • State withholding and SUI rates vary widely and cannot be treated as flat numbers.
  • A correct calculator uses the current-year IRS tables and the employee's specific W-4 fields, not the older allowance model.

Frequently Asked Questions

Do employers pay their half of Social Security separately?

The employer share is not withheld from the employee; it is an additional tax the employer deposits alongside the employee share. Both halves are reported together on Form 941.

Does every state have income tax withholding?

No. Nine states have no state income tax on wages: Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, and Wyoming. Every other state does, and each has its own tables.

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Payroll Tax Calculator 2026: Federal, State & FICA | Swift Paybooks