Unit Converter API

Convert between 300+ units (length, weight, volume, temperature, speed, data, energy, time...) and evaluate math expressions safely (functions, constants, units, matrices).

Authentication & base URL

Subscribe through one of our marketplace listings; your marketplace API key and base URL are shown there. All endpoints return JSON over HTTPS, served from a global edge network (typically 20–150 ms).

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Endpoints

GET `/v1/units/convert`

Convert units

Parameter	In	Description	Example
`value` *	query	Number	`10`
`from` *	query	Unit from	`km`
`to` *	query	Unit to	`mile`

GET `/v1/math/evaluate`

Evaluate expression

Parameter	In	Description	Example
`expr` *	query	Expression	`2*(3+4)^2 + sqrt(16)`

Example

GET /v1/units/convert?value=10&from=km&to=mile

{
  "value": 10,
  "from": "km",
  "to": "mile",
  "result": 6.21371192237,
  "text": "10 km = 6.2137119 mile"
}

Convert between 300+ units (length, weight, volume, temperature, speed, data, energy, time...) and evaluate math expressions safely (functions, constants, units, matrices).

Use cases

Shopping and recipe apps, engineering and education tools, spreadsheets and chatbots that need reliable math.

Why this API

Fast: runs on a global edge network, typical response well under 1 second.
Reliable: simple JSON, clear error messages.
Fair pricing: Free plan 500 requests/month, Pro 25,000 for $4.99, Ultra 150,000 for $14.99.

Pricing

Free plan with 500 calls per month, then Pro (25,000 calls for $4.99/month) and Ultra (150,000 calls for $14.99/month). See all plans.