Self-Employment Tax Calculator
Estimate Social Security and Medicare tax on self-employment income.
How to Use
Enter your net self-employment income (revenue minus business expenses), the calculator applies the standard US self-employment tax formula: 92.35% of that income is subject to a combined 15.3% rate, split into a 12.4% Social Security portion (capped at the wage base you enter) and an uncapped 2.9% Medicare portion. The Deductible Half result shows how much of that total tax can be deducted against income tax separately, a detail easy to overlook but genuinely useful once tax filing season arrives.
Why Self-Employed Workers Pay a Different Tax Than Employees
A traditional employee has Social Security and Medicare split evenly between themselves and their employer, 7.65% withheld from the paycheck, with the employer separately paying a matching 7.65% on top. When you're self-employed, there's no employer to cover that other half, so the self-employment tax formula requires paying both halves yourself, the full 15.3% combined rate (12.4% Social Security + 2.9% Medicare). This is exactly why self-employment tax often feels disproportionately large compared to what a salaried friend sees withheld from their own paycheck, it genuinely is close to double, because you're covering both sides of the same underlying contribution.
Worked Example: Net Income of ₹1,000,000
Using this tool's own defaults, net self-employment income of 1,000,000 and a wage base of 1,400,000. First, only 92.35% of net income counts toward the tax, 1,000,000 × 0.9235 = 923,500. The Social Security portion applies 12.4% to whichever is smaller, that 923,500 figure or the wage base, since 923,500 sits below the 1,400,000 cap, the full amount applies: 923,500 × 12.4% = 114,514. The Medicare portion applies its uncapped 2.9% to the same 923,500 figure regardless of the wage base: 923,500 × 2.9% = 26,781.50. Total self-employment tax comes to 114,514 + 26,781.50 = 141,295.50, and the deductible half for income tax purposes is exactly half that, 70,647.75.
What Happens Once Income Exceeds the Wage Base
The wage base cap only limits the Social Security portion, not Medicare. If net earnings after the 92.35% adjustment exceed the wage base you've entered, the Social Security calculation stops growing at that cap, min(net earnings, wage base) × 12.4%, income above it owes no additional Social Security tax. Medicare, by contrast, keeps applying its 2.9% to every dollar of adjusted net earnings with no ceiling at all. This produces a subtle effect worth understanding: as income rises well past the wage base, the effective combined rate on each additional dollar of income drops from 15.3% down toward just 2.9%, since only the uncapped Medicare portion keeps growing.
Common Mistakes When Estimating Self-Employment Tax
The most frequent mistake is applying the 15.3% rate to gross revenue instead of net income after business expenses, which significantly overstates the tax owed, always deduct legitimate business expenses first. A second mistake is forgetting the 92.35% adjustment entirely and applying 15.3% directly to the full net income figure, overstating the result by roughly 7.65%. A third is using a stale or guessed wage base figure instead of checking the actual current-year IRS number, since this cap changes annually and materially affects the result for anyone with net earnings near or above it.
Planning for the Bill: Why Quarterly Estimates Matter
Because self-employment income typically has no automatic withholding the way a salaried paycheck does, the full self-employment tax liability (along with income tax) usually needs to be paid proactively through estimated quarterly payments rather than arriving as one lump surprise at filing time. Running this calculator periodically through the year, as actual net income becomes clearer, rather than only once at year end, makes it much easier to set aside the right amount for each quarterly payment and avoid underpayment penalties that can apply when too little is paid throughout the year relative to the eventual total liability.
Frequently Asked Questions
Why is only 92.35% of my income taxed?
The US self-employment tax formula applies the 15.3% rate to 92.35% of net earnings rather than the full amount, as a rough equivalent to how an employer's share of payroll tax isn't counted as taxable income for a traditional employee.
What is the Social Security wage base, and why is it editable?
It's the maximum amount of earnings subject to the 12.4% Social Security portion each year, income above that cap only owes the 2.9% Medicare portion. This figure is adjusted annually by the IRS, so it's left editable, enter the current year's figure for an accurate result.
What is the "deductible half" shown in the results?
The IRS allows self-employed taxpayers to deduct half of their self-employment tax when calculating adjusted gross income for regular income tax purposes, this mirrors how an employer's half of payroll tax is never counted as an employee's taxable income in the first place. This deduction reduces income tax owed, it does not reduce the self-employment tax itself, which is calculated in full on the net earnings figure.
Is self-employment tax the same as income tax?
No, they're separate taxes calculated independently and owed in addition to each other. Self-employment tax specifically covers the Social Security and Medicare contributions that an employer and employee would normally split between them, income tax is calculated separately using ordinary tax brackets on your total taxable income from all sources. A self-employed person typically owes both, this calculator only estimates the self-employment tax portion.
Do I owe self-employment tax on every dollar I earn from freelance or side work?
Self-employment tax applies to net self-employment earnings, that is, revenue minus legitimate business expenses, not gross revenue. In the US, self-employment tax generally only applies once net self-employment earnings for the year exceed a small minimum threshold (commonly $400), below that threshold it typically doesn't apply at all, though normal income tax rules may still require reporting the income.
Why does only the Social Security portion have a wage base cap, but not Medicare?
This mirrors the design of the underlying benefit programs. Social Security benefits are calculated with a cap on the earnings that count toward them, so the corresponding tax is capped too, income above the wage base doesn't earn additional Social Security benefit credit, so it isn't taxed for that purpose. Medicare, by contrast, applies uncapped to all net earnings, which is why the 2.9% Medicare portion in this calculator is never limited by the wage base field, only the 12.4% Social Security portion is.