Free Self-Employment Tax Calculator — Quarterly Schedule & Safe Harbor

Last updated: April 17, 2026

MoneyMath's self-employment tax calculator estimates 2026 Social Security and Medicare self-employment tax, quarterly payment amounts, deduction impact, and safe-harbor planning.

Free to useRuns in your browserSource-backed assumptions

Free self-employment tax calculator with quarterly payment schedule. See exact dates and amounts, first-year freelancer shock (W-2 vs 1099), deduction impact, and safe harbor rule to avoid penalties.

Use the Self-Employment Tax Calculator to compare realistic scenarios before making a money, health, or planning decision.

Adjust the inputs and review the result breakdown so you can see which assumptions matter most.

How to use this calculator

Step 1Enter your starting information. Add the core inputs requested by the Self-Employment Tax Calculator, such as amounts, dates, rates, income, weight, or other scenario details.
Step 2Review the calculated result. Read the headline answer first, then scan the supporting breakdown, chart, or comparison table.
Step 3Compare another scenario. Change one input at a time to understand what drives the result and which option is most realistic.

Formula, Sources & Assumptions

Formula

Self-employment tax applies Social Security and Medicare rates to 92.35% of net self-employment earnings, subject to the Social Security wage base.

Assumptions

Self-employment tax uses the 2026 Social Security wage base.
Quarterly payments are estimated by dividing annual tax into four payments.
Penalty rates change quarterly and are not calculated as a precise penalty schedule.

Sources

SSA 2026 Social Security changesOASDI wage base and FICA context.
IRS estimated taxesEstimated tax rules and payment timing.
IRS 2026 tax inflation adjustmentsFederal brackets, standard deduction, and indexed tax items.