Documentation sections

Quickstart

Three steps: get a key, call the endpoint, use the result. The call beside this text is a link budget; any calculator works the same way.

Three steps

Get an API key. A free key on your dashboard covers 5 calls a month. Pro ($9 a month) covers 100 and API ($19 a month) 10,000; see pricing. A program can get its user a key without a paste: see the device grant.
Call the endpoint. POST to /api/py/v1/calculate with a slug and its inputs, and your key in the X-API-Key header.
Use the result. Read values by output key, check warnings and errors, and keep provenance if you need to say how a figure was computed.

Keep the key out of your code

The examples read the key from RFTOOLS_API_KEY. The Python library also reads the key that rftools login saved, so a script never holds it.

Shell

export RFTOOLS_API_KEY=rfc_…
# or, with the Python library installed:
rftools login

Inputs and units

Each calculator takes its inputs in the units its page shows, by the keys its reference lists, with their ranges and defaults. Send every input: most are required, and a call without one is refused (400) and costs nothing; one a calculator can do without takes the default its reference shows. The provenance lists every input the values were computed from.

Try a request in the browser with your key.
Errors: what each status means and what the SDK raises.
Quotas and limits: the monthly allowance and the per-minute limits.

curl -X POST https://rftools.io/api/py/v1/calculate \
  -H "X-API-Key: $RFTOOLS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "slug": "rf-link-budget",
    "inputs": {
      "txPower": 20,
      "txGain": 2,
      "txCableLoss": 1,
      "frequency": 2400,
      "distance": 0.5,
      "rainFade": 0,
      "atmosphericLoss": 0.5,
      "pointingLoss": 0,
      "extraLossCount": 0,
      "extraLoss1": 0,
      "extraLoss2": 0,
      "extraLoss3": 0,
      "extraLoss4": 0,
      "rxGain": 2,
      "rxCableLoss": 1,
      "rxSensitivity": -90,
      "targetMargin": 10
    }
  }'

import rftools

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

result = client.calculate("rf-link-budget", {
    "txPower": 20,
    "txGain": 2,
    "txCableLoss": 1,
    "frequency": 2400,
    "distance": 0.5,
    "rainFade": 0,
    "atmosphericLoss": 0.5,
    "pointingLoss": 0,
    "extraLossCount": 0,
    "extraLoss1": 0,
    "extraLoss2": 0,
    "extraLoss3": 0,
    "extraLoss4": 0,
    "rxGain": 2,
    "rxCableLoss": 1,
    "rxSensitivity": -90,
    "targetMargin": 10,
})
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": "rf-link-budget",
    "inputs": {
      "txPower": 20,
      "txGain": 2,
      "txCableLoss": 1,
      "frequency": 2400,
      "distance": 0.5,
      "rainFade": 0,
      "atmosphericLoss": 0.5,
      "pointingLoss": 0,
      "extraLossCount": 0,
      "extraLoss1": 0,
      "extraLoss2": 0,
      "extraLoss3": 0,
      "extraLoss4": 0,
      "rxGain": 2,
      "rxCableLoss": 1,
      "rxSensitivity": -90,
      "targetMargin": 10
    }
  }),
});
console.log(response.status, await response.json());

package main

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

func main() {
	body := []byte(`{
	  "slug": "rf-link-budget",
	  "inputs": {
	    "txPower": 20,
	    "txGain": 2,
	    "txCableLoss": 1,
	    "frequency": 2400,
	    "distance": 0.5,
	    "rainFade": 0,
	    "atmosphericLoss": 0.5,
	    "pointingLoss": 0,
	    "extraLossCount": 0,
	    "extraLoss1": 0,
	    "extraLoss2": 0,
	    "extraLoss3": 0,
	    "extraLoss4": 0,
	    "rxGain": 2,
	    "rxCableLoss": 1,
	    "rxSensitivity": -90,
	    "targetMargin": 10
	  }
	}`)
	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": "rf-link-budget",
  "values": {
    "fspl": 94.03140814283587,
    "eirp": 21,
    "rxPower": -72.53140814283587,
    "linkMargin": 17.468591857164128,
    "maxRangeKm": 3.73593745752468,
    "totalAdditionalLoss": 0.5,
    "wavelength": 124.91352416666666,
    "fresnelRadius": 3.951479535671839,
    "maxRangeAtTarget": 1.181407156171655
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:rf-link-budget",
    "version": "api@3f2c1a9b04de",
    "formulaRef": "Friis, \"A Note on a Simple Transmission Formula\" (1946)",
    "assumptions": [],
    "validRange": {
      "status": "inside",
      "bounds": {
        "txPower": {
          "min": -30,
          "max": 100,
          "unit": "dBm"
        },
        "txGain": {
          "min": -30,
          "max": 60,
          "unit": "dBi"
        },
        "txCableLoss": {
          "min": 0,
          "max": 20,
          "unit": "dB"
        },
        "frequency": {
          "min": 0.1,
          "max": 1000000,
          "unit": "MHz"
        },
        "distance": {
          "min": 0.001,
          "max": 1000000,
          "unit": "km"
        },
        "rainFade": {
          "min": 0,
          "max": 50,
          "unit": "dB"
        },
        "atmosphericLoss": {
          "min": 0,
          "max": 20,
          "unit": "dB"
        },
        "pointingLoss": {
          "min": 0,
          "max": 10,
          "unit": "dB"
        },
        "extraLossCount": {
          "min": 0,
          "max": 4,
          "unit": ""
        },
        "extraLoss1": {
          "min": 0,
          "max": 50,
          "unit": "dB"
        },
        "extraLoss2": {
          "min": 0,
          "max": 50,
          "unit": "dB"
        },
        "extraLoss3": {
          "min": 0,
          "max": 50,
          "unit": "dB"
        },
        "extraLoss4": {
          "min": 0,
          "max": 50,
          "unit": "dB"
        },
        "rxGain": {
          "min": -30,
          "max": 60,
          "unit": "dBi"
        },
        "rxCableLoss": {
          "min": 0,
          "max": 20,
          "unit": "dB"
        },
        "rxSensitivity": {
          "min": -160,
          "max": 0,
          "unit": "dBm"
        },
        "targetMargin": {
          "min": 0,
          "max": 60,
          "unit": "dB"
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "txPower": 20,
      "txGain": 2,
      "txCableLoss": 1,
      "frequency": 2400,
      "distance": 0.5,
      "rainFade": 0,
      "atmosphericLoss": 0.5,
      "pointingLoss": 0,
      "extraLossCount": 0,
      "extraLoss1": 0,
      "extraLoss2": 0,
      "extraLoss3": 0,
      "extraLoss4": 0,
      "rxGain": 2,
      "rxCableLoss": 1,
      "rxSensitivity": -90,
      "targetMargin": 10
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": "An API key is required. Get a free key at https://rftools.io/dashboard/?newKey=1.",
  "errorKind": "invalid_request",
  "keyUrl": "https://rftools.io/dashboard/?newKey=1"
}

No key was sent. keyUrl is where to get one.

Quickstart

Three steps

Keep the key out of your code

Inputs and units

Next