Unit Conversion API Documentation

API Overview

The Unit Conversion API provides accurate, fast, and reliable unit conversions for length, weight, temperature, volume, and area measurements. Perfect for applications, websites, and mobile apps that need conversion functionality.

Key Features

Multiple Conversion Types: Length, Weight, Temperature, Volume, Area
Batch Processing: Convert multiple values in a single request
High Precision: Results accurate to 6 decimal places
Rate Limiting: 1000 requests per hour per session
RESTful Design: Clean, predictable API structure
JSON Responses: Easy to parse and integrate
CORS Enabled: Works from web browsers
No Authentication: Simple to get started

Rate Limits

Free tier: 1000 requests per hour per session. Contact us for higher limits or commercial usage.

Response Format

All responses are in JSON format with consistent structure:

{
  "status": "success|error",
  "timestamp": "2025-06-22T10:30:00+00:00",
  "data": { ... },
  "api_version": "1.0"
}
            

API Endpoints

GET /api.php

Single Conversion via URL Parameters

GET /api.php?type={type}&from={from}&to={to}&value={value}

Parameters:

Parameter	Type	Required	Description
type	string	Yes	Conversion type: length, weight, temperature, volume, area
from	string	Yes	Source unit (e.g., "meters", "kg", "celsius")
to	string	Yes	Target unit (e.g., "feet", "pounds", "fahrenheit")
value	number	Yes	Numeric value to convert

Example:

GET /api.php?type=length&from=meters&to=feet&value=10

POST /api.php

Single or Batch Conversions via JSON

Single Conversion:

{
  "type": "length",
  "from": "meters",
  "to": "feet", 
  "value": 10
}
                

Batch Conversion:

{
  "conversions": [
    {"type": "length", "from": "meters", "to": "feet", "value": 10},
    {"type": "weight", "from": "kg", "to": "pounds", "value": 5},
    {"type": "temperature", "from": "celsius", "to": "fahrenheit", "value": 25}
  ]
}
                

GET /api.php?docs=1

API Documentation (JSON format)

Returns machine-readable API documentation including supported units and examples.

Usage Examples

JavaScript (Fetch API)

// GET request
fetch('https://unitconversioncalc.com/api.php?type=length&from=meters&to=feet&value=10')
  .then(response => response.json())
  .then(data => console.log(data));

// POST request - Single conversion
fetch('https://unitconversioncalc.com/api.php', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    type: 'weight',
    from: 'kg',
    to: 'pounds',
    value: 70
  })
})
.then(response => response.json())
.then(data => console.log(data));

// POST request - Batch conversion
fetch('https://unitconversioncalc.com/api.php', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    conversions: [
      {type: 'length', from: 'meters', to: 'feet', value: 10},
      {type: 'weight', from: 'kg', to: 'pounds', value: 5}
    ]
  })
})
.then(response => response.json())
.then(data => console.log(data));
            

PHP (cURL)

 'temperature',
    'from' => 'celsius',
    'to' => 'fahrenheit',
    'value' => 25
]));
curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
curl_close($ch);
$data = json_decode($response, true);
?>
            

Python (Requests)

import requests

# GET request
response = requests.get('https://unitconversioncalc.com/api.php', params={
    'type': 'volume',
    'from': 'liters',
    'to': 'gallons',
    'value': 10
})
data = response.json()

# POST request
response = requests.post('https://unitconversioncalc.com/api.php', json={
    'type': 'area',
    'from': 'square_meters',
    'to': 'square_feet',
    'value': 100
})
data = response.json()
            

Response Examples

Successful Response:

{ "status": "success", "timestamp": "2025-06-22T10:30:00+00:00", "data": { "success": true, "type": "length", "from": "meters", "to": "feet", "input_value": 10, "result": 32.8084, "formula": "m × 3.28084", "precision": 6 }, "api_version": "1.0" }

Error Response:

{ "status": "error", "error": "Unsupported conversion type: distance. Supported: length, weight, temperature, volume, area", "timestamp": "2025-06-22T10:30:00+00:00", "api_version": "1.0" }

Supported Units

Length

Unit	Aliases	Symbol
Meters	m, meter, meters	m
Centimeters	cm, centimeter, centimeters	cm
Millimeters	mm, millimeter, millimeters	mm
Kilometers	km, kilometer, kilometers	km
Inches	in, inch, inches	in
Feet	ft, foot, feet	ft
Yards	yd, yard, yards	yd
Miles	mi, mile, miles	mi

Weight

Unit	Aliases	Symbol
Grams	g, gram, grams	g
Milligrams	mg, milligram, milligrams	mg
Kilograms	kg, kilogram, kilograms	kg
Pounds	lb, pound, pounds	lb
Ounces	oz, ounce, ounces	oz
Stones	st, stone, stones	st

Temperature

Unit	Aliases	Symbol
Celsius	c, celsius	°C
Fahrenheit	f, fahrenheit	°F
Kelvin	k, kelvin	K

Volume

Unit	Aliases	Symbol
Milliliters	ml, milliliter, milliliters	ml
Liters	l, liter, liters	L
Gallons	gal, gallon, gallons	gal
Quarts	qt, quart, quarts	qt
Pints	pt, pint, pints	pt
Cups	cup, cups	cup
Fluid Ounces	fl_oz, floz, fluid_ounce, fluid_ounces	fl oz
Tablespoons	tbsp, tablespoon, tablespoons	tbsp
Teaspoons	tsp, teaspoon, teaspoons	tsp

Area

Unit	Aliases	Symbol
Square Meters	sqm, sq_m, square_meter, square_meters	m²
Square Centimeters	sqcm, sq_cm, square_centimeter, square_centimeters	cm²
Square Kilometers	sqkm, sq_km, square_kilometer, square_kilometers	km²
Hectares	hectare, hectares, ha	ha
Square Feet	sqft, sq_ft, square_foot, square_feet	ft²
Square Inches	sqin, sq_in, square_inch, square_inches	in²
Square Yards	sqyd, sq_yd, square_yard, square_yards	yd²
Acres	acre, acres	ac
Square Miles	sqmi, sq_mi, square_mile, square_miles	mi²

API Tester

Test the API directly from this page:

Conversion Type:

From Unit:

To Unit:

Value:

Error Codes

HTTP Code	Error Type	Description	Solution
400	Bad Request	Missing or invalid parameters	Check required parameters and formats
405	Method Not Allowed	Unsupported HTTP method	Use GET or POST methods only
429	Rate Limit Exceeded	Too many requests per hour	Wait for rate limit reset or upgrade plan
500	Internal Server Error	Server-side error	Contact support if persistent

Common Error Messages

"Missing required parameters" - Include type, from, to, and value
"Value must be numeric" - Ensure value is a valid number
"Unsupported conversion type" - Use: length, weight, temperature, volume, area
"Unsupported unit" - Check supported units list
"Invalid JSON input" - Verify JSON syntax for POST requests

Code Libraries & SDKs

JavaScript Library

class UnitConverter {
  constructor(baseUrl = 'https://unitconversioncalc.com/api.php') {
    this.baseUrl = baseUrl;
  }

  async convert(type, from, to, value) {
    const response = await fetch(
      `${this.baseUrl}?type=${type}&from=${from}&to=${to}&value=${value}`
    );
    return await response.json();
  }

  async batchConvert(conversions) {
    const response = await fetch(this.baseUrl, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ conversions })
    });
    return await response.json();
  }
}

// Usage
const converter = new UnitConverter();
converter.convert('length', 'meters', 'feet', 10)
  .then(result => console.log(result));
            

PHP Class

baseUrl = $baseUrl;
  }
  
  public function convert($type, $from, $to, $value) {
    $url = $this->baseUrl . "?type=$type&from=$from&to=$to&value=$value";
    $response = file_get_contents($url);
    return json_decode($response, true);
  }
  
  public function batchConvert($conversions) {
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $this->baseUrl);
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode(['conversions' => $conversions]));
    curl_setopt($ch, CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    $response = curl_exec($ch);
    curl_close($ch);
    return json_decode($response, true);
  }
}

// Usage
$converter = new UnitConverter();
$result = $converter->convert('weight', 'kg', 'pounds', 70);
?>
            

Python Class

import requests

class UnitConverter:
    def __init__(self, base_url='https://unitconversioncalc.com/api.php'):
        self.base_url = base_url
    
    def convert(self, type_name, from_unit, to_unit, value):
        response = requests.get(self.base_url, params={
            'type': type_name,
            'from': from_unit,
            'to': to_unit,
            'value': value
        })
        return response.json()
    
    def batch_convert(self, conversions):
        response = requests.post(self.base_url, json={
            'conversions': conversions
        })
        return response.json()

# Usage
converter = UnitConverter()
result = converter.convert('temperature', 'celsius', 'fahrenheit', 25)
            

Need Help?

Contact us at api@unitconversioncalc.com for:

Custom SDK development
Higher rate limits
Enterprise support
Custom conversion types
Integration assistance