PayCalc — what's left of your US paycheck
Bilingual calculator for all 50 states. Works out federal, FICA and state tax with the 2026 tables, and has its own page per state.
"How much of my paycheck is left after taxes" is one of the most repeated — and least well answered — searches on the US web. PayCalc answers it per state, in two languages.
The problem
Search demand is huge and granular: people look up their net pay by state, by pay frequency, and by filing status. A single page won't rank for that; it needs programmatic surface plus a calculation engine that is correct, not approximate.
The approach
- A pure, testable tax engine in
src/lib/tax.ts: federal brackets, FICA, state tax, and the child tax credit, over data intax2026.ts. - Programmatic SEO: dynamic
[state]routes generate one page per state viagenerateStaticParams, plus per-state and per-city comparisons and FAQs. - Bilingual EN/ES through a
[lang]segment andAccept-Languagenegotiation inproxy.ts. - Data UX: donut breakdown, US map, comparison bars, and a take-home table — all client-side over the same engine.
// One engine, one typed result — the UI only formats it
export function calculateTakeHome(input: CalcInputs): CalcResult;The result
All 50 states covered with indexable pages, JSON-LD for rich results, sitemap.ts + robots.ts, and Sentry + Vercel Analytics for production observability. The calculation is deterministic and isolated, so it can be tested without rendering the UI.