Unit Converter API docs
Convert values between units of length, mass, volume, area, speed, temperature, digital storage and time. Pure, precise, and deterministic.
Authentication
All Unit Converter API requests authenticate via two headers. Get your API key from your RapidAPI dashboard after subscribing on the Basic (free) tier or higher.
X-RapidAPI-Key: YOUR_API_KEY X-RapidAPI-Host: unit-converter-by-helix-api.p.rapidapi.com
Base URL
https://unit-converter-by-helix-api.p.rapidapi.com
Endpoints
GET
/convertConvert a value between two units
GET
/unitsList supported units (optionally by category)
Code Examples
Python
import requests
url = "https://unit-converter-by-helix-api.p.rapidapi.com/convert"
headers = {
"X-RapidAPI-Key": "YOUR_API_KEY",
"X-RapidAPI-Host": "unit-converter-by-helix-api.p.rapidapi.com",
}
response = requests.get(url, headers=headers)
print(response.json())JavaScript
const response = await fetch(
"https://unit-converter-by-helix-api.p.rapidapi.com/convert",
{
method: "GET",
headers: {
"X-RapidAPI-Key": "YOUR_API_KEY",
"X-RapidAPI-Host": "unit-converter-by-helix-api.p.rapidapi.com"
}
}
);
const data = await response.json();cURL
curl -X GET "https://unit-converter-by-helix-api.p.rapidapi.com/convert" \ -H "X-RapidAPI-Key: YOUR_API_KEY" \ -H "X-RapidAPI-Host: unit-converter-by-helix-api.p.rapidapi.com"
Response Format
All endpoints return JSON in this consistent envelope:
{
"status": "ok",
"data": { /* endpoint-specific payload */ },
"meta": {
"cached": false,
"latency_ms": 142,
"request_id": "req_abc123"
},
"timestamp": "2026-05-21T12:00:00Z"
}Error Codes
| HTTP | Code | Meaning |
|---|---|---|
| 400 | BAD_REQUEST | Missing or invalid parameter |
| 401 | UNAUTHORIZED | Invalid or missing API key |
| 403 | FORBIDDEN | Your plan doesn't include this endpoint |
| 429 | RATE_LIMIT_EXCEEDED | Too many requests — back off and retry |
| 500 | INTERNAL_ERROR | Something went wrong on our side |
| 503 | UPSTREAM_UNAVAILABLE | A third-party data source is down |
Common Use Cases
Recipe & cooking apps
Engineering tools
Health & fitness
E-commerce internationalization
Educational platforms
3D printing dimension converter
Nutrition label unit conversion
Scientific lab measurement tool
Construction material calculator
Fuel economy converter
Fabric and textile measurement tool
Agricultural land area converter
Medical dosage calculator
Shipping weight and volume converter
HVAC BTU calculator
Photography exposure converter
Brewing recipe unit scaler
Network bandwidth converter
Astronomy distance unit converter
Electrical unit converter