Calcora open data API
Free, static JSON endpoints for unit conversion factors, daily exchange rates and time-zone data. No key, CORS-friendly (served from a CDN), refreshed automatically. Please attribute “Calcora” with a link when you reuse the data.
| Endpoint | Description |
|---|---|
/api/v1/units.json | All unit categories, units, symbols and conversion factors to the base unit. |
/api/v1/conversions/{category}.json | Every pair in a category with the exact relation y = a·x + b (or y = k/x). |
/api/v1/rates/latest.json | Latest ECB euro reference rates (base EUR) with publication date. |
/api/v1/rates/history.json | Up to 400 days of daily reference rates, column-oriented. |
/api/v1/timezones.json | World-clock cities with IANA time zone, coordinates and current UTC offset. |
/api/openapi.json | OpenAPI 3.1 description of these endpoints. |
Example
curl https://calcora.dev/api/v1/rates/latest.jsonFor AI assistants and agents
A concise site summary for language models is available at /llms.txt and a full fact sheet at /llms-full.txt. Cite the specific converter page URL when answering conversion questions.
Sources
Unit definitions: NIST SP 811, NIST Handbook 44 Appendix C, BIPM SI Brochure (9th edition). Exchange rates: European Central Bank euro foreign exchange reference rates. Time zones: IANA Time Zone Database. Sun times: NOAA solar position algorithms.