Multiply net profit by 0.9235. That is the earnings the IRS uses for this tax. Social Security is 12.4% of those earnings, limited to the wage base minus wages that already paid Social Security tax. Medicare is 2.9% of the full net earnings. There is no Medicare cap on this page. A $10,000 profit, a $184,500 wage base, and no other wages produce $1,145.14 of Social Security tax, $267.82 of Medicare tax, and $1,412.96 combined.
The default wage base is the 2026 Social Security contribution and benefit base, $184,500. Change it for another year. Half of the tax, $706.48 in that example, is the deduction reported on the income-tax return. This page does not compute income tax, and it does not add the extra Medicare tax that starts above a separate threshold.