Employee FICA has two core components
For 2026, the employee Social Security rate is 6.2% and the employee Medicare rate is 1.45% on covered wages. Employers generally pay matching amounts for the ordinary Social Security and Medicare taxes. These taxes are calculated separately from federal income-tax withholding.
That separation matters because a W-4 change can alter federal withholding without changing ordinary Social Security or Medicare tax. Likewise, a deduction may reduce federal taxable wages but remain subject to FICA.
The Social Security wage base makes year-to-date wages important
Social Security tax applies only up to the annual wage base. For 2026, the wage base is $184,500. Once covered Social Security wages for the year reach that amount, additional covered wages are no longer subject to the employee 6.2% Social Security tax for that year.
If an employee enters the year with $183,500 of Social Security wages and receives another $3,000 of otherwise covered wages, only $1,000 remains below the 2026 wage base. A paycheck calculator that ignores year-to-date wages would overstate Social Security withholding in that situation.
Medicare has no wage base
Ordinary Medicare tax does not stop at the Social Security wage base. Covered Medicare wages continue to be subject to the 1.45% employee tax. In addition, employers must begin withholding the 0.9% Additional Medicare Tax when wages paid to an employee exceed $200,000 during the calendar year, regardless of the employee's filing status.
The employee's final Additional Medicare Tax liability on the tax return can depend on filing status and combined wages, but the employer withholding trigger is based on wages the employer pays over $200,000. That is why year-to-date Medicare wages are a useful input for paycheck estimation.
Why your FICA wages may differ from gross pay
Some benefit deductions can reduce Social Security and Medicare wages, while others do not. A traditional 401(k) contribution commonly reduces federal income-tax wages but not FICA wages. Certain qualifying cafeteria-plan benefits can reduce FICA wages. Payroll records and the plan's actual tax treatment control; a public calculator can only apply the classification selected by the user.
When reconciling a pay stub, compare the Social Security wage and Medicare wage lines—not just gross pay—to the tax amounts. That will usually explain why multiplying gross pay by the headline rate does not always reproduce the payroll result.
Official references
These sources are provided so you can verify the rules or concepts summarized above. PayCalc uses primary government sources where they are available.