How freelance take-home pay is estimated
Profit = revenue − business expenses. From profit the calculator subtracts retirement contributions (treated as tax-deductible), social or self-employment contributions, and income tax on the remaining taxable income. Use your average (effective) income tax rate for a quick estimate, or your marginal rate to be conservative.
Defaults reflect a US-style setup (15.3% SE tax, half deductible). In the UK, Germany, India or elsewhere, replace the rates with your local contribution and income tax rates. US freelancers can get an exact SE tax figure from the self-employment tax calculator.