Estimate your US self-employment tax (the 15.3% Social Security + Medicare on net earnings), your effective rate, and the half you can deduct. 2026 figures.
When you work for an employer in the US, you and the employer split the Social Security and Medicare taxes — you each pay 7.65%, and you mostly never see the employer's half. When you're self-employed, you are the employer, so you pay both halves yourself: that's self-employment (SE) tax, a combined 15.3% made up of 12.4% Social Security and 2.9% Medicare. It's separate from, and in addition to, federal and state income tax — which is why so many first-year freelancers are shocked at tax time.
The math has three steps:
1. Taxable base = net self-employment income × 0.9235. The 0.9235 factor (1 − 7.65%) removes the employer-equivalent portion from the base, so you're not taxed on the part an employee wouldn't be.
2. Social Security = 12.4% × base, up to the annual Social Security wage limit (about $184,500 for 2026). Earnings above that limit are not subject to the 12.4% portion.
3. Medicare = 2.9% × the entire base — there is no cap on the Medicare portion.
Add steps 2 and 3 for your total SE tax. Example: on $80,000 of net income, the base is $80,000 × 0.9235 = $73,880; Social Security is 12.4% = $9,161; Medicare is 2.9% = $2,143; total SE tax ≈ $11,304, an effective rate of about 14.1% of net income (slightly below 15.3% because of the 0.9235 factor).
There's a meaningful offset: you can deduct one-half of your SE tax from your gross income when calculating your income tax. It's an above-the-line deduction, so you get it whether or not you itemize. It does not reduce the SE tax itself — you still owe the full amount — but it lowers the income on which your income tax is figured. In the example above, that's about $5,652 shaved off your taxable income.
High earners owe an extra 0.9% Medicare surtax on earnings above a threshold — $200,000 for single filers, $250,000 for married filing jointly. It sits on top of the 2.9% Medicare portion and is not reduced by the 0.9235 factor. This calculator estimates the base 15.3% SE tax; if your earnings are above the threshold, add the 0.9% on the excess separately. Most self-employed people below those incomes won't need to.
SE tax is only one layer. On top of it you'll owe federal income tax (and usually state income tax) on your profit. A rough planning habit many freelancers use: set aside 25–35% of net income for taxes overall — SE tax plus income tax — though your real number depends on your bracket and state. Because no employer withholds for you, the IRS expects quarterly estimated payments; underpaying through the year can trigger penalties. Estimate early so the bill isn't a surprise.
SE tax is charged on net income, so every legitimate business expense you deduct reduces both your income tax and your SE tax. Track them carefully. Retirement contributions (SEP-IRA, Solo 401(k)) and, for some, electing S-corporation status can change the picture at higher incomes — but those are decisions to make with a tax professional, not a calculator. Use this tool to size the liability; use a CPA to optimize it.
Net income × 0.9235 = base; 12.4% Social Security on the base up to the wage limit + 2.9% Medicare on all of it = 15.3% combined up to the cap.
It removes the employer-equivalent 7.65% from the base, mirroring how employees aren't taxed on the employer's share.
Yes — you deduct one-half from gross income for income-tax purposes (above-the-line). It lowers income tax, not the SE tax itself.
An extra 0.9% on earnings above $200k single / $250k MFJ, on top of the 2.9%. Add it separately if you're above the threshold.