How self-employment tax is calculated
Self-employment tax covers Social Security and Medicare. It is 15.3% of 92.35% of your net profit: 12.4% for Social Security, up to the 2026 wage base of $184,500, and 2.9% for Medicare with no cap.
You also owe income tax on your profit. This estimate applies your top federal bracket and your state rate to your profit after deducting half of the self-employment tax.
What this estimate leaves out
It does not include the standard deduction, the qualified business income deduction, credits, the extra 0.9% Medicare tax on high earners, or wages from a job that already count toward the Social Security wage base. Treat it as a savings target, not a tax return.
The formulas behind it
Every result cell is a plain spreadsheet formula, so you can check the math or rebuild it yourself.
| Cell | Result | Formula |
|---|---|---|
| B8 | Net profit | =B2-B3 |
| B9 | Earnings subject to SE tax | =B8*92.35% |
| B10 | Self-employment tax | =MIN(B9,184500)*12.4%+B9*2.9% |
| B11 | Income tax (estimate) | =(B8-B10/2)*(B4%+B5%) |
| B12 | Set aside this year | =B10+B11 |
| B13 | Each quarterly payment | =B12/4 |
| B14 | Share of income to save | =B12/B2 |
Sources
Rates checked September 2026. Platforms change fees from time to time.