Physics Constants API

Free static API for all 355 CODATA 2022 fundamental physical constants — values, uncertainties, units. No auth, no rate limit, no cost. Just JSON.

Read the docs Try the explorer Source on GitHub

Try it

Request:

curl https://constants.oriz.in/constants/speed-of-light-in-vacuum.json

Response:

{
  "slug": "speed-of-light-in-vacuum",
  "name": "speed of light in vacuum",
  "value": 299792458,
  "value_string": "299 792 458",
  "uncertainty": null,
  "uncertainty_string": "exact",
  "unit": "m s^-1",
  "exact": true,
  "category": "universal",
  "source": "CODATA 2022 (NIST)",
  "source_url": "https://physics.nist.gov/cuu/Constants/"
}

How to use

via constants.oriz.in

Cloudflare Pages, custom domain, free TLS. Recommended for browser apps.

https://constants.oriz.in/constants/planck-constant.json

via jsDelivr

Pinned to a git ref. Recommended for production code that wants reproducibility.

https://cdn.jsdelivr.net/gh/oriz-org/constants-api@main/constants/planck-constant.json

Stats

Constants: 355
Categories: 6
Dataset: CODATA 2022
Code license: MIT
Cost: ₹0/mo

Why use this

· Static JSON files — no API key, no rate limit, no quota.
· Served from Cloudflare Pages and jsDelivr edge caches.
· CODATA 2022 official values — pinned to a git ref for reproducible builds.
· Single GitHub source of truth — fork it, audit it, send a PR.

API reference → CODATA source (NIST) →