Free tool
Four questions. One number. Free.
Your result is an estimate based on the answers you enter. It is not filed anywhere.
Method
The estimate uses expected net self-employment profit: client revenue minus ordinary business expenses. That is the useful starting point for Schedule C income and self-employment tax, rather than the larger number that passed through your bank account.
The regular federal calculation generally applies the combined 15.3% Social Security and Medicare rate to 92.35% of net self-employment earnings. The Social Security portion has an annual ceiling, and higher earnings can trigger additional Medicare tax, so the tool adjusts rather than multiplying every dollar by one flat rate. IRS explanation.
The calculator subtracts the applicable standard deduction before applying progressive federal brackets. It also models the deduction for the employer-equivalent half of self-employment tax and an estimated qualified business income deduction of up to 20% when the answers indicate it may apply. Filing status, other household income and deduction limits can materially change the result.
State treatment is simplified into a practical reserve estimate based on the state selected. Some states have no individual income tax; others use brackets, flat rates, local taxes or separate business charges. Treat this part as a planning buffer, not a substitute for the state return instructions.
Questions
The standard rate combines 12.4% for Social Security and 2.9% for Medicare. Under the regular method, it generally applies to 92.35% of net self-employment earnings. Annual Social Security limits and additional Medicare tax rules can change the final amount.
The tool uses a state estimate rather than pretending every state works the same way. Your actual amount can differ because states use different rates, deductions, credits, local taxes and business-level charges.
The result gives an annual reserve and a quarterly planning amount. It does not determine your exact payment schedule, prior-year safe-harbor amount or how much withholding from another job may already cover.
Use expected net business profit after ordinary business expenses, not gross client payments. Keep a little extra in the reserve when your expense estimate is still mostly optimism with a spreadsheet attached.