Unit converter API: length, mass, volume, temperature, data size
Convert between units of length, mass, volume (incl. US cups and gallons), temperature (c, f, k), speed, area, data size (kB vs KiB), time, energy and pressure. Example units: km, mi, lb, kg, floz, ml, mph, kn, acre, gib, kwh, psi. Use when exact conversions matter.
When to use it
- Convert km to mi, lb to kg, floz to ml, mph to kn, kWh, psi and more
- Tell kB from KiB in data sizes
- Convert temperatures between c, f and k
Inputs
| Name | Type | Description |
|---|---|---|
value (required) | number | The amount |
from (required) | string | Unit to convert from |
to (required) | string | Unit to convert to |
Request
Over HTTP, with a card key from /credits:
curl -H "Authorization: Bearer adt_…" "https://tools.funwords.eu/units/convert?value=10&from=km&to=mi"Or one of your 25 free calls, no key:
curl "https://tools.funwords.eu/units/convert?value=10&from=km&to=mi&trial=1"Without a key, the same URL answers 402 Payment Required with x402 and MPP terms, so an agent with a wallet pays per call in USDC (Base, Polygon, Arbitrum or Solana over x402; Base or Tempo over MPP) and retries.
Example result
{
"value": 10,
"from": "km",
"to": "mi",
"kind": "length",
"result": 6.2137119224
}From an AI agent (MCP)
Add the MCP server to Claude, Cursor or any MCP client. This tool is units_convert, and the first 25 successful calls are free:
https://tools.funwords.eu/mcpQuestions
Which unit kinds?
Length, mass, volume (incl. US cups and gallons), temperature, speed, area, data size, time, energy and pressure.
How do I pay?
Each successful call costs $0.01; failed calls are not charged. The first 25 calls are free. Then pay with card credits (from $1; the key goes in an Authorization header or, for clients that can only fetch a URL, as api_key= in the URL) or per call in USDC over x402 or MPP. No account is needed.