Business profit
Annual gross receipts equal the weekly amount multiplied by modeled workweeks. Documented business mileage is split by the effective IRS rate period, then combined with other eligible business-expense assumptions.
The arithmetic can show a business loss, while self-employment tax and current-year QBI are floored at zero. Loss limitations, carryovers, vehicle elections, mixed-use allocation, depreciation, and basis require return-level analysis beyond this tool.
- Annual receipts = weekly receipts × workweeks
- Mileage deduction = first-half miles × $0.725 + second-half miles × $0.76
- Modeled Schedule C profit = receipts − mileage deduction − other business expenses
Self-employment taxes
The model multiplies business profit by 92.35%. The Social Security portion uses the 2026 wage base remaining after user-entered W-2 Social Security wages, while regular Medicare has no wage cap.
Additional Medicare tax is calculated separately because it is not included in the deductible one-half of regular self-employment tax. This matters for mixed W-2 and self-employment income.
Federal income tax and QBI
The simplified federal model combines user-entered other ordinary income with adjusted business income, applies the chosen filing status and basic 2026 standard deduction, and runs the remainder through progressive brackets.
The estimate assumes the taxpayer is under 65, not blind, and not another taxpayer’s dependent. QBI is limited by qualified business income and taxable income before the deduction; complicated phase-ins, capital gains, specified-service businesses, retirement deductions, health insurance, and tip coordination may require Form 8995 or 8995-A.
State planning amount
State results are deliberately approximate. States without a broad individual wage income tax use 0% in this layer; most others use a neutral 4.5% planning rate and the District of Columbia uses 6%.
This is not a reproduction of state brackets, local income tax, credits, franchise tax, paid-leave programs, or special self-employment rules. The assumption is displayed and can be treated as a cash cushion, not a filing result.
Fuel defaults and privacy
Fuel defaults come from EIA regular-gas retail data. Only nine selected states have direct weekly state series; other states use a named PADD regional proxy and are labeled as such. A monthly value is used only as a fallback at the same geographic level.
The EIA key runs only in a server-side update job. The deployed site receives a static, validated JSON snapshot without a key. Calculator inputs remain in the browser and expire from local storage after seven days.
Verification and known limits
Pure calculation engines are covered by boundary and regression tests. The generated site is checked for routes, canonical tags, metadata, structured data, accessible controls, mobile viewports, and secret leakage.
The site does not calculate credits, alternative minimum tax, net investment income tax, local tax, withholding reconciliation, underpayment penalties, every QBI phase-in, or a complete state return. Results are rounded for display while calculations retain cents.
Primary sources
- IRS 2026 inflation adjustments (Rev. Proc. 2025-32)
- SSA 2026 contribution and benefit base
- IRS Topic 554: Self-employment tax
- IRS Publication 463: car expenses and mileage records
- IRS Announcement 2026-11: midyear mileage rate
- IRS 2026 Form 1040-ES
- EIA gasoline and diesel fuel update methodology
- Public Law 119-21: QBI deduction and active-business minimum
By the GigTakeHome Editorial Team · Content last reviewed: August 13, 2026. Report an error.