How to use the self-employment tax calculator
- Enter your net profit from Schedule C (income after expenses).
- Enter the Social Security wage base (2026: $176,100) — only earnings up to it are taxed for Social Security.
- Answer whether the 0.9 percent Additional Medicare surtax applies to you.
- Read the total SE tax and the deduction you take on your 1040.
Worked example
A sole proprietor with $60,000 net profit has an SE base of $55,410 (92.35%). Social Security is $6,871 (12.4% of the base, under the cap), Medicare is $1,607 (2.9%), for a total SE tax of $8,478. The deduction is $4,239 — one half of the SE tax.
The math
Base = Net profit x 92.35%
Social Security = 12.4% x min(Base, wage base)
Medicare = 2.9% x Base + 0.9% x (Base over $200,000)
Deduction = SE tax / 2
The 92.35 percent base exists because the employer half of the tax is itself deductible, so Congress lets you skip that portion when figuring the tax. The 50 percent deduction then removes the employer half from your taxable income. This estimate uses the single-filer Additional Medicare threshold of $200,000; married filers using joint returns hit it at $250,000.