Methodology & sources

Exactly how our calculators work, which figures they use and where those figures come from.

Updated October 19, 2026 · Tax year 2026 · Figures last verified 2026-10-19

What the calculators estimate

Each tool estimates US federal tax on self-employment income, plus an optional flat state tax you enter yourself. The delivery and rideshare tools also estimate profit after vehicle costs. Everything runs in your browser using the JavaScript on the page, and no input is sent anywhere.

Figures used for tax year 2026

Standard deduction	$16,100 single · $32,200 married filing jointly · $24,150 head of household
Top of each federal bracket (single)	10% to $12,400 · 12% to $50,400 · 22% to $105,700 · 24% to $201,775 · 32% to $256,225 · 35% to $640,600 · 37% above
Self-employment tax	15.3% on 92.35% of net profit (12.4% Social Security + 2.9% Medicare)
Social Security wage base	$184,500
Additional Medicare tax	0.9% above $200,000 single / $250,000 joint
Business mileage rate	72.5¢ (Jan–Jun 2026) · 76¢ (from July 1, 2026)
Qualified tips deduction	Up to $25,000, phased out above $150,000 / $300,000 income
Home office (simplified)	$5 per sq ft, up to 300 sq ft

The calculation, step by step

1. Net profit = income − business expenses (including the mileage deduction for drivers)

2. Self-employment tax = 12.4% × min(0.9235 × profit, wage base − W-2 wages) + 2.9% × 0.9235 × profit (+ 0.9% above the threshold)

3. Adjusted gross income = profit + W-2 wages − half of self-employment tax

4. Taxable income = AGI − standard deduction − qualified tips deduction − QBI deduction

5. QBI deduction = the smaller of 20% of (profit − half of SE tax) and 20% of taxable income before QBI

6. Federal income tax = progressive brackets applied to taxable income

7. Tax attributable to this income = total tax with the income − total tax without it

Step 7 matters if you also have a regular job. Your employer already withholds on your wages, so the estimate counts only the extra tax your side income causes. Quarterly payments are that amount divided by four.

Driver profit model

Cash profit = earnings − gas (miles ÷ mpg × price) − other car costs (miles × your rate) − other expenses. Take-home = cash profit − estimated tax. For tax purposes the calculator uses the IRS standard mileage deduction instead of your actual car costs, because you cannot deduct both for the same vehicle. The weekly figures are scaled to the number of weeks you enter to estimate a full year.

What the calculators do not include

Tax credits such as the child tax credit or earned income credit.
Itemized deductions, retirement contributions, health insurance deductions and other adjustments.
The alternative minimum tax, capital gains and investment income.
QBI deduction limits that apply at higher incomes (we show a warning when they may matter).
State and local taxes beyond a flat rate you enter.
Tax-reporting forms and filing requirements. A tax professional can advise on your return.

How we keep figures current

All yearly values sit in one configuration block in the calculator code and are checked against the sources below when the IRS and SSA publish new numbers. Mid-year changes, such as the IRS raising the 2026 mileage rate from 72.5 to 76 cents on July 1, are reflected as soon as we verify them. If you spot an error, tell us at hello@gigprofitmath.com.