Most tax calculators on the internet are black boxes. You type in a number, a result appears, and you're expected to trust it. Some get the math wrong in ways that cost people money — applying SE tax to the wrong base, forgetting the half-SE deduction, or using last year's brackets.
IndieCalc takes the opposite approach. This page documents every step of our calculation, the exact sources we use, the assumptions we make, and the limitations we're upfront about. If you find an error, tell us.
The Calculation Pipeline
When you enter your income and hit calculate, IndieCalc runs seven steps in sequence. Each step feeds into the next. Here's the full pipeline, with the formulas:
Social Security tax is 12.4% of your SE taxable base, but only up to the wage base ($184,500 for 2026, per the SSA). Every dollar of SE base above $184,500 is exempt from Social Security tax.
Medicare tax is 2.9% on all SE taxable earnings, with no cap. An additional 0.9% Medicare surtax kicks in on earnings above $200,000 (single) or $250,000 (joint).
Medicare = SE base × 0.029
Additional Medicare = max(0, SE base - threshold) × 0.009
Total SE tax = Social Security + Medicare + Additional Medicare
AGI = Net income - Half-SE deduction - other above-the-line deductions
The Qualified Business Income deduction (made permanent by the OBBBA) lets most freelancers deduct 20% of their net business income from their taxable income. We calculate it as 20% of the SE taxable base.
The OBBBA also introduced a $400 minimum QBI deduction for anyone with at least $2,000 in qualifying business income. Phase-outs for specified service trades begin at $191,950 (single) / $383,900 (joint) — we note this but do not model the full phase-out, since it requires information about your specific trade that a calculator can't reliably capture.
Federal tax = sum of (income in each bracket × bracket rate)
A Complete Worked Example
To show every step in action, here's the full calculation for a single freelancer earning $100,000 in net self-employment income, living in Georgia, with QBI enabled and no children:
| Net self-employment income | $100,000 |
| Step 1: SE taxable base ($100K × 92.35%) | $92,350 |
| Step 2: Social Security ($92,350 × 12.4%) | $11,451 |
| Step 2: Medicare ($92,350 × 2.9%) | $2,678 |
| Step 2: Total SE tax | $14,130 |
| Step 3: Half-SE deduction | ($7,065) |
| Step 4: QBI deduction ($92,350 × 20%) | ($18,470) |
| Step 5: Standard deduction | ($16,100) |
| Step 5: Federal taxable income | $58,365 |
| Step 5: Federal income tax (brackets) | $7,617 |
| Step 7: Georgia state tax (5.19% flat, $12K deduction) | $4,574 |
| Total tax (SE + federal + state) | $26,321 |
| Take-home pay | $73,679 |
Effective total rate: 26.3%. Quarterly estimated payment: $6,580.
Our Data Sources
Every number in IndieCalc traces back to an official or authoritative source. We don't use AI-generated estimates, crowdsourced data, or "approximately" figures. Here's what we use and where it comes from:
| Data Point | Source |
|---|---|
| Federal brackets | Tax Foundation — 2026 Federal Tax Brackets, cross-referenced with IRS Revenue Procedure |
| Standard deductions | IRS Revenue Procedure for Tax Year 2026 |
| SE tax rate | IRS Self-Employment Tax Center: 15.3% (12.4% SS + 2.9% Medicare) on 92.35% of net earnings |
| SS wage base | Social Security Administration: $184,500 for 2026 |
| QBI deduction | IRC §199A, as amended by OBBBA: 20% of QBI, $400 minimum, permanent |
| Child Tax Credit | IRS — Child Tax Credit: $2,200/child per OBBBA |
| Senior deduction | OBBBA §[TBD]: $6,000 for taxpayers 65+, phases out at $75K/$150K |
| State brackets | Tax Foundation — 2026 State Rates, cross-referenced with individual state revenue department publications |
| SALT cap | OBBBA: $40,400 for 2026, through 2029 |
We update data annually when the IRS, SSA, and state agencies publish new figures, typically between October and January. The current data is for the 2026 tax year. We'll add 2027 data when the IRS publishes it (expected October 2026).
What We Don't Model
No calculator can replace a tax professional, and we're deliberate about what we include vs. omit. Here's what IndieCalc does not currently account for:
- Itemized deductions. We use the standard deduction. If you itemize (mortgage interest, charitable contributions, medical expenses), your federal tax may be lower than what we show.
- QBI phase-outs for specified service trades. We note the threshold but don't reduce the QBI deduction above it, since determining eligibility requires details about your specific business type.
- Local/city income taxes. NYC, Philadelphia, Ohio municipalities, and Maryland counties all levy local income taxes that can add 1%–4% to your bill. We note these in the state descriptions but don't calculate them.
- Alternative Minimum Tax (AMT). Unlikely to affect most freelancers at typical income levels, but relevant for high earners with specific deduction patterns.
- Multi-state income. If you earn income in multiple states, apportionment rules apply. We calculate for a single state of residence.
- State-specific credits. Many states offer credits (earned income, property tax, dependent care) that reduce your state tax below what we calculate.
In every case where our estimate diverges from reality, it will tend to overestimate your tax, not underestimate it. We consider this the safer direction for planning purposes.
Privacy by Design: Your Data Stays in Your Browser
IndieCalc runs entirely in your browser. When you enter your income and click calculate, the math happens on your device using JavaScript. No data is sent to any server.
- No income data is transmitted, stored, or logged
- No cookies are set for tracking purposes
- No third-party analytics scripts are loaded
- No account creation is required
You can verify this yourself: open your browser's developer tools, switch to the Network tab, and run a calculation. You'll see zero outgoing requests. The entire calculation engine is in two files (tax-data.js and calculator.js) that load once when the page opens and run locally from then on.
One exception: if you click "Open in Gmail" or "Open in Outlook.com" from the email-report dropdown, your tax estimate is included in the compose URL and sent to that service so it can pre-fill the message. The "Default mail app" and "Copy to clipboard" options stay entirely on your device.
For the full details, see our privacy policy.
Why We Built This
Most tax calculators are lead generation tools. They give you a number, then ask for your email, then sell your contact information to accountants and financial advisors. The calculators themselves are often afterthoughts — a reason to get you on the page, not a tool built to be useful.
IndieCalc started as a spreadsheet one of us built to understand our own freelance taxes. We kept improving it — adding states, accounting for the OBBBA changes, handling edge cases like the SS wage cap and Additional Medicare — until it outgrew the spreadsheet. We turned it into a website because every other self-employment tax calculator we found was either inaccurate, outdated, or trying to sell us something.
The goal is simple: give freelancers a tool that's accurate, transparent, private, and free. If we get the math wrong, let us know and we'll fix it.
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