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Methodology

US FICA Tax Calculator methodology

Estimate bounded employee FICA for one 2026 US wage payment without implying income-tax or take-home-pay accuracy. Scope: United States, 2026 calendar year. Official source: Internal Revenue Service Publication 15 (2026), reviewed 27 July 2026.
Duc Nguyen X.By Duc Nguyen X.· Founder, Wage101Last reviewed: View update historyMethodology

Educational only: Work and pay decision support, not tax, legal, financial or career advice.

Privacy: Calculations run locally; Wage101 does not receive your work or pay inputs.

Update policy: Reviewed when formulas or official dependencies change.

Scope: US work and pay planning using your own assumptions.

1. Formulas and units

Total employee FICA
totalEmployeeFica = socialSecurityTax + medicareTax + additionalMedicareTax

Where

totalEmployeeFica
Total employee FICA (USD/payment)Source: Calculated output
socialSecurityTax
Employee Social Security (USD/payment)Source: Calculated output
medicareTax
Employee Medicare (USD/payment)Source: Calculated output
additionalMedicareTax
Additional Medicare withheld (USD/payment)Source: Calculated output
Social Security
socialSecurityTax = min(grossWages, max(0, 184500 − priorSocialSecurityWages)) × 0.062

Where

grossWages
Gross wages in this payment (USD/payment)Source: User assumption
socialSecurityTax
Employee Social Security (USD/payment)Source: Calculated output
Medicare
medicareTax = grossWages × 0.0145

Where

grossWages
Gross wages in this payment (USD/payment)Source: User assumption
medicareTax
Employee Medicare (USD/payment)Source: Calculated output
Additional Medicare withholding
additionalMedicareTax = newlyCrossedEmployerThresholdWages × 0.009

Where

additionalMedicareTax
Additional Medicare withheld (USD/payment)Source: Calculated output
FICA wages
ficaWages = grossWages

Where

grossWages
Gross wages in this payment (USD/payment)Source: User assumption
ficaWages
FICA wage basis (USD/payment)Source: Calculated output
Federal income-tax wage basis before other adjustments
federalIncomeTaxWagesBeforeOtherAdjustments = grossWages − pretax401kContribution

Where

grossWages
Gross wages in this payment (USD/payment)Source: User assumption
pretax401kContribution
Pretax 401(k) contribution in this payment (USD/payment)Source: User assumption
federalIncomeTaxWagesBeforeOtherAdjustments
Federal income-tax wage basis before other adjustments (USD/payment)Source: Calculated output

Money inputs and outputs use USD. Pay, time, benefits and work-related costs use the units stated beside each input.

2. Worked example

Input assumptions

Calculate one $5,000 payment after $50,000 of prior Social Security and Medicare wages.

Calculation and outputs

Example

Calculate one $5,000 payment after $50,000 of prior Social Security and Medicare wages.

Total employee FICA
382.50 currency units
Employee Social Security
310.00 currency units
Employee Medicare
72.50 currency units
Additional Medicare withheld
0.00 currency units
FICA wage basis
5,000.00 currency units
Federal income-tax wage basis before other adjustments
4,500.00 currency units

Employee Social Security, Medicare and Additional Medicare withholding remain separate.

Interpretation

Use this only as bounded employee FICA withholding, not complete tax or take-home pay.

3. Validation and boundary checks

  • All wage and contribution amounts are finite and non-negative.
  • Pretax 401(k) contribution cannot exceed gross wages.
  • The Social Security wage base is applied using prior year-to-date wages.

4. Assumptions and source classification

  • The employer wage bases entered immediately precede this payment.
  • All entered gross wages are employee FICA wages.
  • The official 2026 constants are fixed and are not editable assumptions.

Official dependencies used by this calculator are captured in the Wage101 evidence register and version-acknowledged in this page history. User-entered work and pay assumptions remain separate from those official inputs.

5. Limitations

  • Federal, state and local income-tax withholding and final tax liability are excluded.
  • Additional Medicare uses the employer withholding threshold, not filing-status liability.
  • Employer taxes, benefits, exemptions, corrections and full take-home pay are excluded.

This is educational decision support, not personalised tax, legal, financial or career advice. Check how the rules that apply in United States treat your work and pay circumstances, and seek qualified advice where appropriate.

6. Update and evidence policy

Registered family-level suites test formula invariants and example reconciliation; the release ledger records that coverage without claiming a separate oracle for every line of public copy. Registered official sources block dependent public workflows when their evidence or version acknowledgement is unavailable or invalid. Work and pay inputs remain user-supplied because they vary by person, job and contract.

Change history

  1. : Initial public release of the US FICA Tax planner and methodology.

Related reading

Use these practical guides to interpret the decision and its assumptions.

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