JSON API

Free, fast, CORS-enabled JSON API for unit conversions. No key required for basic GETs. All responses are edge-cached for 24 hours and use NIST-exact factors where defined.

Endpoints

GET /api/v1/convert — single conversion
GET /api/v1/table — reference table
GET /api/v1/units — unit catalog
GET /api/v1/formula — formula data for a pair

/api/v1/convert

GET https://convertnavi.com/api/v1/convert?value=10&from=kg&to=lb

Parameters:

value (number, required) — input value
from (slug or alias, required) — source unit
to (slug or alias, required) — target unit
precision (0-12, optional) — decimal digits
ingredient (slug, optional) — for volume↔mass cooking conversions
locale (BCP-47 tag, optional) — for `formatted` string formatting

Sample response:

{
  "ok": true,
  "from": {
    "slug": "kilogram",
    "name": "Kilogram",
    "symbol": "kg",
    "system": "SI"
  },
  "to": {
    "slug": "pound",
    "name": "Pound",
    "symbol": "lb",
    "system": "imperial"
  },
  "input": 10,
  "output": 22.046226218487757,
  "formatted": "22.0462",
  "exact": true,
  "source": "NIST: 1 lb = 0.45359237 kg exact.",
  "lastValidatedAt": "2026-06-14T15:53:07.581Z"
}

/api/v1/table

GET https://convertnavi.com/api/v1/table?from=celsius&to=fahrenheit&values=0,25,100
GET https://convertnavi.com/api/v1/table?from=kg&to=lb&range=0-100&step=10&format=csv

Sample response:

{
  "ok": true,
  "from": "celsius",
  "to": "fahrenheit",
  "rows": [
    {
      "input": 0,
      "output": 32,
      "formatted": "32"
    },
    {
      "input": 25,
      "output": 77,
      "formatted": "77"
    },
    {
      "input": 100,
      "output": 212,
      "formatted": "212"
    }
  ]
}

/api/v1/units

GET https://convertnavi.com/api/v1/units
GET https://convertnavi.com/api/v1/units?category=pressure

Returns a list of all available units with slug, name, symbol, aliases, category, system and source.

Rate limits & terms

Basic use is free and unauthenticated. We aggressively cache at the edge — please add a polite User-Agent so we can reach you if your traffic looks unusual. For production volume, contact us about pinned SLA & higher rate limits.