Unit Converter API

About the Unit Converter API

A unit conversion API that replaces hand-maintained conversion tables in your code. It covers 185 units across 23 measures, so the everyday conversions are one call each: liters to gallons, miles per hour to kilometers per hour, Celsius to Fahrenheit, megabytes to gigabytes, psi to bar, pounds to kilograms, and kilowatt-hours to joules. Beyond length, area, mass, volume and temperature it handles time, speed, pace, pressure, digital storage, parts per million, frequency, angles, illuminance, volume flow rate and electrical units from volts and amperes to watts and kilowatt-hours. Results are rounded to 2 decimal places. On paid plans, precision returns up to 10 decimal places, so very small results no longer round to zero, and conversions=true returns the same value in every unit of its measure in one call, such as a mass in micrograms through metric tons.

What people use it for

Measurement Converters

Convert measurements such as weight, length, area, temperature, and more by using the Unit Converter API. Use the API to convert units between different systems

Unit Standardization

Standardize units across different systems by using the Unit Converter API. Convert units to a common standard for consistency and compatibility

Unit Calculation

Perform unit calculations by using the Unit Converter API to convert units in mathematical operations. Use the API to simplify unit conversions in calculations

Without writing code

The Unit Converter widget from WidgetSpark converts from your desktop.

Ways to call it

One endpoint, many ways in — REST with JSON, XML, YAML and CSV, plus GraphQL and an MCP interface for AI agents.

JSON

Default REST response

XML

Markup format

YAML

Human-readable

CSV

Tabular export

Beta

GraphQL

Query language

New

MCP

For AI agents

Request parameters — GET /v1/unitconverter

Sent in the query string. Premium parameters are accepted on every plan but only take effect on plans that include them. Anything not listed here is dropped rather than passed through.

Required

Optional

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curl "https://api.apiverve.com/v1/unitconverter?value=100&from=lb&to=kg&precision=4&conversions=true" \
  -H "x-api-key: YOUR_API_KEY"

Authentication

Send your key in the x-api-key header. That is the only auth step — no token exchange, and no per-endpoint scope to configure.

Response — GET /v1/unitconverter

Every APIVerve endpoint returns the same three top-level keys, so one response handler covers your whole integration: status, error and data. Only data changes shape.

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{
  "status": "ok",
  "error": null,
  "data": {
    "result": {
      "result": 45.36,
      "from": "100 lb",
      "to": "kg"
    },
    "unitDefinitions": {
      "from": {
        "abbr": "lb",
        "measure": "mass",
        "system": "imperial",
        "singular": "Pound",
        "plural": "Pounds"
      },
      "to": {
        "abbr": "kg",
        "measure": "mass",
        "system": "metric",
        "singular": "Kilogram",
        "plural": "Kilograms"
      }
    },
    "conversions": {
      "mcg": 45359200000,
      "mg": 45359200,
      "g": 45359.2,
      "kg": 45.36,
      "mt": 0.05,
      "oz": 1600,
      "lb": 100,
      "t": 0.05
    }
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Response headers

Every response carries your balance, so your own code always knows where it stands without polling anything. All four are exposed to browsers through CORS.

Errors

Read the HTTP status first, then error for the specific reason. The body names the parameter that has to change.

What a call costs — 1 credits per call

Credits are shared across every APIVerve API — one balance, one key, one bill. Failed requests never count against it, so a rejected input costs nothing.

Calls are what the credits buy at this API's rate — spend them here, on any of the other APIs, or across both. Nothing is reserved per endpoint.

Zero-code embed — one snippet, no backend

Drop an interactive Unit Converter form onto any page. The widget calls the API for you, so no key ever appears in your markup and there is nothing to deploy.

Changelog — Unit Converter API

Every change to this endpoint, newest first. Breaking changes ship as a new version and the previous one keeps serving — response fields are added, never removed or retyped in place, so an integration written against v1 keeps working.

Currently v1