How self-employment tax is calculated
Self-employment tax is the Social Security and Medicare tax for people who work for themselves. The ordinary calculation starts with business net profit—not gross revenue—and applies the Schedule SE adjustment before separate Social Security and Medicare portions are calculated.
The widely stated 15.3% combined rate is 12.4% Social Security plus 2.9% Medicare. It is not applied directly to gross business income, and the Social Security component may be reduced by covered employee wages.
What the 92.35% adjustment means
After deductible business expenses determine positive net profit, the ordinary Schedule SE calculation multiplies that profit by 92.35%. The result is net earnings from self-employment for this calculation.
Do not subtract 7.65% or half of self-employment tax before using the calculator. For zero or a business loss, this limited calculation keeps the result unchanged and estimates no self-employment tax; it does not decide whether a loss is deductible.
Social Security and Medicare portions
The Social Security portion applies a 12.4% rate only to taxable net earnings that fit inside the remaining annual wage base. The ordinary Medicare portion applies 2.9% to all taxable net earnings and has no ordinary wage cap.
Additional Medicare Tax at 0.9% is a separate calculation involving filing-status thresholds and combined wages, compensation, and self-employment income. It is not included in this estimate.
How the 2026 Social Security wage base works
The 2026 Social Security contribution and benefit base is $184,500. Covered wages and self-employment earnings share this combined annual limit for the Social Security portion.
Once covered wages and eligible self-employment earnings use the full base, further self-employment earnings are not subject to the ordinary 12.4% Social Security portion. Medicare can continue because it does not use this cap.
How W-2 wages affect self-employment tax
Social Security wages and tips generally reported in W-2 boxes 3 and 7 use the wage base before self-employment earnings. Other already determined covered amounts may also matter. Do not substitute Medicare wages from box 5.
The entered covered wages determine only the base remaining for the Social Security portion. TaxArith does not recalculate tax on those wages, and the wages do not reduce the 2.9% Medicare portion of self-employment tax.
The $400 net earnings threshold
The ordinary $400 threshold applies after positive net profit is multiplied by 92.35%. It is not a $400 business-profit threshold; a profit of $400 produces only $369.40 of adjusted net earnings in this calculation.
TaxArith compares the unrounded adjusted result with exactly $400. Church employee income and other special situations can follow rules outside this calculator.
The deductible portion of self-employment tax
The calculator shows 50% of estimated self-employment tax as the potential employer-equivalent adjustment to income. That amount can affect a separate federal income tax calculation.
The adjustment does not reduce self-employment tax itself, is not a tax credit, and does not directly create a refund. This tool does not calculate the actual income-tax savings from the adjustment.
Self-employment tax versus federal income tax
Self-employment tax funds Social Security and Medicare and is calculated separately from ordinary federal income tax. The same business profit can affect both calculations, but their rates, deductions, thresholds, and credits are different.
This result is therefore not a final tax bill or take-home pay. Use a separate income-tax calculation and include other applicable federal, state, and local obligations.
How estimated tax payments relate to self-employment tax
Estimated payments are payments against tax liability. They may help cover self-employment tax and income tax, but making or entering a payment does not reduce the underlying calculated liability.
This calculator does not determine quarterly installments, safe-harbor amounts, due dates, underpayment penalties, or interest. Those payment-planning questions require a broader tax estimate.
What this calculator does not include
TaxArith does not determine deductible business expenses or prepare Schedule C, Schedule SE, or Form 1040. It excludes Additional Medicare Tax, federal income tax, QBI, health-insurance and retirement deductions, state and local tax, payroll withholding, unemployment taxes, penalties, and interest.
Farm and nonfarm optional methods, church employee and minister rules, exemptions, multiple businesses, spouse combinations, basis and passive-loss limitations, S corporation compensation, Forms 4137 and 8919 calculations, and railroad retirement calculations are also outside scope. An actual filed result may differ.
Official 2026 tax data and update status
Self-employment tax data verified for tax year 2026 on August 11, 2026. The $184,500 Social Security wage base and applicable rates are confirmed by the IRS 2026 Form 1040-ES and draft Schedule SE. The available 2026 Schedule SE was published by the IRS as a draft and is not for filing.
Final forms, instructions, or a change in law can alter filing details. TaxArith uses static published data and does not make runtime requests to the IRS.