Calculations you can trust.
Data you don't have to maintain.
Use 150+ verified calculators in your browser, call them from any application via REST API, or give your AI agent accurate tools via MCP.
150+ calculatorsAuthoritative sourcesVersioned dataNo sign-up required
One engine. Three ways to use it.
Calculations worth calling an API for
Writing a formula is easy. Keeping country tax brackets, public holiday calendars, purchasing-power tables, and survival-rate datasets accurate and up to date is the work you shouldn't have to do.
Public holidays by country
2026 calendars for 30+ countries — automatically updated each year.
Income tax calculations
Current-year brackets for multiple jurisdictions. No manual updates.
Purchasing power parity
Convert a salary between countries at equivalent purchasing power, not the market rate.
Business survival rates
BLS Business Employment Dynamics cohort data — 589 rows across 19 sectors.
Try it now — free tier included, no card required:
curl https://api.stupidlyclever.com/v1/public-holidays?country=GB&year=2026 \
-H "Authorization: Bearer YOUR_KEY"Ready to add verified calculation power to your app?
Free tier included — 1,000 API calls/month, no credit card required.