Transparency
Overview
Every calculation on this site runs through a single engine (src/lib/tax/engine.ts) that
reads all rates and thresholds from a single data file (src/data/or-2026.json). No rate is
hard-coded into any page or component. That means the numbers are internally consistent across all 20+
pages, and updating a rate in one place updates the entire site.
The input model
The calculator accepts gross income — as an annual salary or a per-period salary — plus filing status, the number of withholding allowances, and a region (outside Portland, the Metro district, or Multnomah County). From gross it derives the taxable base for each tax layer.
The five layers and their bases
The engine computes five layers in a fixed order, each on its correct base:
- Federal income tax — computed on taxable income = gross − standard deduction ($16,100 single / $32,200 married filing jointly / $24,150 head of household), using the progressive 2026 federal brackets.
- FICA — Social Security at 6.2% up to the $184,500 wage base, plus Medicare at 1.45% with no cap. An extra 0.9% Medicare surtax applies to wages above $200,000 for single filers ($250,000 married).
- Oregon income tax — the four brackets (4.75%, 6.75%, 8.75%, 9.9%) applied to the Oregon base wage = gross − the federal tax subtraction (up to $8,750, phased out above $125,000 single / $250,000 married) − the Oregon standard deduction ($2,910 single / $5,820 married), then a $263-per-allowance credit.
- State payroll taxes — the Statewide Transit Tax at 0.1% of gross (no cap) plus Paid Leave Oregon at 0.6% of gross up to a $184,500 cap.
- Local taxes — for Metro-region workers, the 1% SHS tax on wages above $125,000 single / $250,000 married, capped at $250,000 of wages; for Multnomah County residents, the PFA at 1.5% above $125,000 and 3% above $250,000, with no cap.
This is the order real Oregon withholding follows, and it is why the calculator’s per-check figures line up with actual stubs within a few dollars.
Bonus income
Bonus and supplemental pay uses Oregon’s flat 8% supplemental withholding rate on the bonus, plus the standard FICA, state, payroll and local rates on the same bonus. The federal side uses the flat 22% supplemental method most employers use.
Self-employment income
Self-employment income uses the SE tax rate of 15.3% applied to 92.35% of net profit, with half of the SE tax deducted as an adjustment to income. Federal income tax is computed on profit minus the SE tax deduction and the standard deduction; Oregon tax uses the same base as wage income.
Overtime
Hourly overtime is computed at 1.5× the regular rate for hours over 40 in a workweek, per the federal Fair Labor Standards Act, and is taxed through the same five layers as regular wages.
2026 figures in the data file
The following figures are used for the 2026 tax year and live in src/data/or-2026.json:
federal standard deductions and brackets; the $184,500 Social Security wage base and $200,000 Medicare
surtax threshold; Oregon’s brackets, standard deductions ($2,910 / $5,820), allowance credit ($263) and
federal tax subtraction (max $8,750, phased out by $1,750 steps above $125,000 / $250,000); the 0.1%
transit tax, 0.6% Paid Leave rate with its $184,500 cap; and the Metro SHS and Multnomah PFA rates and
thresholds.
Known simplifications
The calculator is an estimate, not a tax filing. It does not model itemized deductions, tax credits, dependents beyond allowances, capital gains, the $35 Arts Tax, or the Workers Benefit Fund assessment. Withholding tables round per period, so a real stub may differ from the annual model by a few dollars. It is not affiliated with the State of Oregon, the IRS, or any local government.
Primary sources
Every figure is tied to a primary source:
- Oregon brackets, standard deductions, allowance credit and federal tax subtraction: Oregon Department of Revenue, 2026 Withholding Instructions and OR-W-4, oregon.gov/dor.
- Federal brackets, standard deduction and 22% supplemental rate: IRS Rev. Proc. 2025-32 and IRS Publication 15 (Circular E).
- Social Security wage base ($184,500) and Medicare surtax: Social Security Administration, 2026 wage base announcement.
- Statewide Transit Tax and Paid Leave Oregon: Oregon Employment Department, 2026 payroll tax guidance.
- Metro SHS and Multnomah PFA rates: Metro and Multnomah County ordinances, verified 2026.
All figures were verified on 2026-08-05 and are re-checked when the site’s data file is updated.