Documentation sections

Temperature Unit Converter

POSThttps://rftools.io/api/py/v1/calculate

Slug temperature-converter. Convert temperature between Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur scales. Useful for thermal analysis, datasheet comparison, and engineering calculations.

Inputs

Send every one of these in inputs, in the units shown. Most are required: a call without one is refused (400) and costs nothing; one the calculator can do without takes the default shown. An input outside its range is still computed and flagged in the provenance.

Inputs of temperature-converter
Name	Unit	Range	Default	Description
celsiusnumber	°C	at least −273.15	25	Temperature in degrees Celsius

Outputs

Returned in values, by key. A value that is unbounded or undefined is null.

Outputs of temperature-converter
Field	Unit	Description
fahrenheitheadline	°F	Temperature in degrees Fahrenheit: F = C × 9/5 + 32
kelvin	K	Temperature in Kelvin (absolute scale): K = C + 273.15
rankine	°R	Temperature in degrees Rankine (absolute Fahrenheit scale): R = K × 9/5
reaumur	°Ré	Temperature in degrees Réaumur: Ré = C × 4/5

Calling it

Calculate: one call, the request and response in full, and its errors.
Batch: this calculator with others, or a sweep, in one request.
Solve for a target: the value of one input that brings an output to a target.

curl -X POST https://rftools.io/api/py/v1/calculate \
  -H "X-API-Key: $RFTOOLS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "slug": "temperature-converter",
    "inputs": {
      "celsius": 25
    }
  }'

import rftools

client = rftools.Client()  # reads RFTOOLS_API_KEY, or the key `rftools login` saved

result = client.calculate("temperature-converter", {"celsius": 25})
print(result.values)
print(result.warnings, result.provenance.formula_ref)

const response = await fetch("https://rftools.io/api/py/v1/calculate", {
  method: "POST",
  headers: {
    "X-API-Key": process.env.RFTOOLS_API_KEY,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "slug": "temperature-converter",
    "inputs": {
      "celsius": 25
    }
  }),
});
console.log(response.status, await response.json());

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"os"
)

func main() {
	body := []byte(`{
	  "slug": "temperature-converter",
	  "inputs": {
	    "celsius": 25
	  }
	}`)
	req, err := http.NewRequest("POST", "https://rftools.io/api/py/v1/calculate", bytes.NewReader(body))
	if err != nil {
		panic(err)
	}
	req.Header.Set("X-API-Key", os.Getenv("RFTOOLS_API_KEY"))
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(res.Status, string(out))
}

application/json

{
  "slug": "temperature-converter",
  "values": {
    "fahrenheit": 77,
    "kelvin": 298.15,
    "rankine": 536.67,
    "reaumur": 20
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:temperature-converter",
    "version": "api@3f2c1a9b04de",
    "formulaRef": null,
    "assumptions": [],
    "validRange": {
      "status": "inside",
      "bounds": {
        "celsius": {
          "min": -273.15,
          "max": null,
          "unit": "°C"
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "celsius": 25
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": [
    {
      "type": "float_parsing",
      "loc": [
        "body",
        "inputs",
        "celsius"
      ],
      "msg": "Input should be a valid number, unable to parse string as a number",
      "input": "abc"
    }
  ]
}

An input sent as text. Nothing was counted.

{
  "detail": "More than 120 requests in 60 seconds from this address.",
  "errorKind": "rate_limited",
  "limit": 120,
  "windowSeconds": 60,
  "upgradeUrl": "https://rftools.io/pricing/"
}

Too many requests in a minute, with Retry-After.

Same inputs on the calculator pageTemperature Unit Converter, at these values