Calculator
Enter your numbers, then calculate. Rates and caps are editable for different years or assumptions.
Example data table
| Scenario | Net profit | Other wages | Estimated total tax |
|---|---|---|---|
| Side business, no wages | $30,000 | $0 | Varies by rates and caps |
| Consulting plus salary | $60,000 | $120,000 | Often lower Social Security portion |
| Higher profit, cap reached | $180,000 | $0 | Social Security capped; Medicare continues |
Use the calculator above to compute exact values for your inputs.
Formula used
This calculator follows a common structure:
- Net earnings:
net_earnings = net_profit × net_earnings_factor - Remaining wage base:
remaining = max(0, wage_base − other_wages) - Social Security taxable:
ss_taxable = min(net_earnings, remaining) - Social Security tax:
ss_tax = ss_taxable × ss_rate - Medicare tax:
med_tax = net_earnings × medicare_rate - Additional Medicare tax:
addl_tax = max(0, net_earnings + other_wages − threshold) × addl_rate - Total:
total = ss_tax + med_tax + addl_tax
Since rates and caps vary by year and region, the “Advanced assumptions” section lets you set the numbers you need.
How to use this calculator
- Pick an input method: net profit, or gross minus expenses.
- Enter business numbers for the same time period.
- Add any other wages to model wage-base interactions.
- Open advanced assumptions to adjust rates and caps.
- Click Calculate to view results above the form.
- Use CSV/PDF buttons to save or share your estimate.
For planning, run multiple scenarios and compare the totals.
Understand what “net earnings” represents
Self-employment tax is typically based on net earnings, not gross receipts. Net earnings start with your net profit, then apply an adjustment factor to approximate the portion treated as earnings for Social Security and Medicare calculations. This step matters because it reduces the base before any rates are applied, which can change planning for quarterly payments and cash reserves. Accurate net profit inputs should exclude personal expenses and reflect ordinary necessary business costs. Keeping clean records makes the estimate more reliable and reduces surprises when completing annual returns or reconciling payments during final filing season.
Model Social Security caps and wage interactions
The Social Security portion is capped by an annual wage base. If you also earn wages from employment, those wages can consume part of the cap, leaving less room for self-employment earnings to be taxed at the Social Security rate. The calculator subtracts other wages from the wage base to estimate remaining capacity, then taxes only the smaller of net earnings or remaining capacity.
Estimate Medicare and additional Medicare exposure
Unlike Social Security, Medicare tax generally applies to all net earnings. Higher combined income may also trigger an additional Medicare component above a threshold that depends on filing status. By entering other wages and selecting a filing status, you can see when the additional component activates and how much of your earnings falls into that higher band.
Use the half-tax deduction for income-tax planning
Many taxpayers can treat half of the self-employment tax as an adjustment when estimating taxable income. This does not reduce the self-employment tax itself, but it can lower income tax in a separate step. The calculator shows an optional half-tax estimate so you can coordinate withholding, estimated payments, and savings targets more realistically.
Run scenarios to support pricing and budgeting decisions
Because rates and caps can change by year, the assumptions section is editable, letting you update the wage base and rates without rebuilding the page. Try multiple profit levels, add expected wages, and compare effective tax rates across scenarios. The CSV and PDF exports help you share estimates with a partner or advisor and document your planning rationale.
FAQs
What is the difference between net profit and net earnings?
Net profit is your business profit after expenses. Net earnings apply an adjustment factor to estimate the portion treated as earnings for these payroll-style taxes, so the taxable base is usually lower than net profit.
How do other wages affect the Social Security portion?
W-2 wages can use up part of the annual wage base. The calculator reduces the remaining base by your wages, so self-employment earnings above that remaining amount are not taxed again for Social Security.
Why can Medicare tax continue when Social Security stops?
The Social Security component has an annual cap. Medicare generally applies to all net earnings without that cap, and an additional Medicare rate can apply above a filing-status threshold.
Does the half-tax deduction reduce what I owe here?
No. It is an income-tax adjustment estimate shown for planning. It can reduce taxable income on a separate calculation, but it does not change the self-employment tax computed on this page.
Can I use this for a different year or country?
Use it as a model. Update the wage base, rates, and thresholds in the assumptions section to match your rules. For non-US systems, confirm whether an adjustment factor or cap works differently.
How should I use results for quarterly planning?
Run a conservative scenario and divide the annual total into four payments as a starting point. Then adjust for seasonal income, withholding from wages, and prior payments to avoid overpaying or underpaying.