API Documentation

Convert a value from one unit to another.

Query Parameters

Parameter	Type	Description
category	string	Category slug (e.g., length, temperature)
from	string	Source unit symbol (e.g., km, C)
to	string	Target unit symbol (e.g., mi, F)
value	number	The numeric value to convert

Example

curl "https://units.30twelve.org/api/v1/convert?category=length&from=km&to=mi&value=5"

Response

{
  "from": { "value": 5.0, "unit": "km", "name": "Kilometer" },
  "to": { "value": 3.106856, "unit": "mi", "name": "Mile" },
  "base_value": 5000.0,
  "base_unit": "m",
  "base_unit_name": "Meter",
  "formula": "km × 0.621371",
  "definition_version": "2026-02-09",
  "sources": ["BIPM SI Brochure (9th ed.)"]
}

Convert arrays of values or submit a list of conversion requests.

Example

curl -X POST "https://units.30twelve.org/api/v1/convert-batch" \\
  -H "Content-Type: application/json" \\
  -d '{"category":"length","from":"m","to":"ft","values":[1,2,3]}'

List all available converter categories grouped by section.

Example

curl "https://units.30twelve.org/api/v1/categories"

List all units available for a specific category.

Example

curl "https://units.30twelve.org/api/v1/categories/temperature/units"

Response

{
  "category": "temperature",
  "name": "Temperature",
  "units": [
    { "name": "Celsius", "symbol": "C" },
    { "name": "Fahrenheit", "symbol": "F" },
    { "name": "Kelvin", "symbol": "K" },
    { "name": "Rankine", "symbol": "R" }
  ]
}