Documentation sections

BLE Link Budget & Range Calculator — Bluetooth Low Energy by PHY

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

Slug ble-link-budget. Bluetooth Low Energy link budget by PHY: data rate and Core Specification receiver sensitivity for LE 1M, LE 2M and LE Coded, path loss in free space or the ITU-R P.1238 indoor model, received power, link margin and maximum range.

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 ble-link-budget
Name	Unit	Range	Default	Description
phynumber	none	0 … 3	0	Bluetooth LE physical layer: 1M (1 Mb/s), 2M (2 Mb/s), or the coded PHY at 500 kb/s (S=2) or 125 kb/s (S=8)
txPowernumber	dBm	any	0	The Core Specification allows −20 to +20 dBm
txGainnumber	dBi	any	0	Transmit Antenna Gain
rxGainnumber	dBi	any	0	Receive Antenna Gain
lossesnumber	dB	at least 0	0	Body, Enclosure & Other Losses
frequencynumber	MHz	at least 1	2440	LE channels run from 2402 to 2480 MHz; 2440 MHz is mid-band
pathLossModelnumber	none	0 … 8	2	Free space, or ITU-R P.1238 site-general for an office, corridor, industrial site or conference room, in line of sight (LoS) or not (NLoS)One of: 0 Free space · 1 P.1238 office LoS · 2 P.1238 office NLoS · 3 P.1238 corridor LoS · 4 P.1238 corridor NLoS · 5 P.1238 industrial LoS · 6 P.1238 industrial NLoS · 7 P.1238 conference room LoS · 8 P.1238 conference room NLoS
distancenumber	m	at least 0.01	10	Direct (3-D) distance between the antennas
sensitivityOverridenumber	dBm	at most 0	0	Enter the radio's datasheet sensitivity to replace the Core Specification reference; 0 keeps the reference
extraLossCountnumber	none	0 … 6	0	How many further losses the link adds, such as building entry, foliage, body or polarisation mismatch (0–6)
extraLoss1number	dB	0 … 50	0	A further loss on the link, such as building entry, foliage, body loss or polarisation mismatch
extraLoss2number	dB	0 … 50	0	A further loss on the link, such as building entry, foliage, body loss or polarisation mismatch
extraLoss3number	dB	0 … 50	0	A further loss on the link, such as building entry, foliage, body loss or polarisation mismatch
extraLoss4number	dB	0 … 50	0	A further loss on the link, such as building entry, foliage, body loss or polarisation mismatch
extraLoss5number	dB	0 … 50	0	A further loss on the link, such as building entry, foliage, body loss or polarisation mismatch
extraLoss6number	dB	0 … 50	0	A further loss on the link, such as building entry, foliage, body loss or polarisation mismatch

Outputs

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

Outputs of ble-link-budget
Field	Unit	Description
linkMarginheadline	dB	Link Margin
dataRate	Mb/s	PHY Data Rate
sensitivityUsed	dBm	Receiver Sensitivity Used
pathLoss	dB	Path Loss
receivedPower	dBm	Received Power
maxRange	m	Maximum Range
shadowFadingStd	dB	Shadow-Fading Std (P.1238 σ)
totalLoss	dB	The cable and other losses, the path loss and every extra loss, added

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": "ble-link-budget",
    "inputs": {
      "phy": 0,
      "txPower": 0,
      "txGain": 0,
      "rxGain": 0,
      "losses": 0,
      "frequency": 2440,
      "pathLossModel": 2,
      "distance": 10,
      "sensitivityOverride": 0,
      "extraLossCount": 0,
      "extraLoss1": 0,
      "extraLoss2": 0,
      "extraLoss3": 0,
      "extraLoss4": 0,
      "extraLoss5": 0,
      "extraLoss6": 0
    }
  }'

import rftools

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

result = client.calculate("ble-link-budget", {
    "phy": 0,
    "txPower": 0,
    "txGain": 0,
    "rxGain": 0,
    "losses": 0,
    "frequency": 2440,
    "pathLossModel": 2,
    "distance": 10,
    "sensitivityOverride": 0,
    "extraLossCount": 0,
    "extraLoss1": 0,
    "extraLoss2": 0,
    "extraLoss3": 0,
    "extraLoss4": 0,
    "extraLoss5": 0,
    "extraLoss6": 0,
})
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": "ble-link-budget",
    "inputs": {
      "phy": 0,
      "txPower": 0,
      "txGain": 0,
      "rxGain": 0,
      "losses": 0,
      "frequency": 2440,
      "pathLossModel": 2,
      "distance": 10,
      "sensitivityOverride": 0,
      "extraLossCount": 0,
      "extraLoss1": 0,
      "extraLoss2": 0,
      "extraLoss3": 0,
      "extraLoss4": 0,
      "extraLoss5": 0,
      "extraLoss6": 0
    }
  }),
});
console.log(response.status, await response.json());

package main

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

func main() {
	body := []byte(`{
	  "slug": "ble-link-budget",
	  "inputs": {
	    "phy": 0,
	    "txPower": 0,
	    "txGain": 0,
	    "rxGain": 0,
	    "losses": 0,
	    "frequency": 2440,
	    "pathLossModel": 2,
	    "distance": 10,
	    "sensitivityOverride": 0,
	    "extraLossCount": 0,
	    "extraLoss1": 0,
	    "extraLoss2": 0,
	    "extraLoss3": 0,
	    "extraLoss4": 0,
	    "extraLoss5": 0,
	    "extraLoss6": 0
	  }
	}`)
	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": "ble-link-budget",
  "values": {
    "linkMargin": 6.672644167870494,
    "dataRate": 1,
    "sensitivityUsed": -70,
    "pathLoss": 63.327355832129506,
    "receivedPower": -63.327355832129506,
    "maxRange": 19.01910747302111,
    "shadowFadingStd": 5.01,
    "totalLoss": 63.327355832129506
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:ble-link-budget",
    "version": "api@3f2c1a9b04de",
    "formulaRef": "Bluetooth Core Specification v5.4, Vol 6, Part A, §1–§4; ITU-R P.1238-13, §3.1, Table 2; ITU-R P.525-4, Eq. (3)",
    "assumptions": [
      {
        "code": "core-spec-sensitivity",
        "text": "Unless a datasheet value is entered, the receiver sensitivity is the Core Specification requirement for the PHY, the worst a compliant receiver may have; real radios are often 20 dB or more better."
      },
      {
        "code": "median-path-loss",
        "text": "Path loss is the free-space value or the ITU-R P.1238 site-general median for the environment, with no fade margin; the link margin is what is left for fading."
      }
    ],
    "validRange": {
      "status": "inside",
      "bounds": {
        "phy": {
          "min": 0,
          "max": 3,
          "unit": ""
        },
        "txPower": {
          "min": null,
          "max": null,
          "unit": "dBm"
        },
        "txGain": {
          "min": null,
          "max": null,
          "unit": "dBi"
        },
        "rxGain": {
          "min": null,
          "max": null,
          "unit": "dBi"
        },
        "losses": {
          "min": 0,
          "max": null,
          "unit": "dB"
        },
        "frequency": {
          "min": 1,
          "max": null,
          "unit": "MHz"
        },
        "pathLossModel": {
          "min": 0,
          "max": 8,
          "unit": ""
        },
        "distance": {
          "min": 0.01,
          "max": null,
          "unit": "m"
        },
        "sensitivityOverride": {
          "min": null,
          "max": 0,
          "unit": "dBm"
        },
        "extraLossCount": {
          "min": 0,
          "max": 6,
          "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"
        },
        "extraLoss5": {
          "min": 0,
          "max": 50,
          "unit": "dB"
        },
        "extraLoss6": {
          "min": 0,
          "max": 50,
          "unit": "dB"
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "phy": 0,
      "txPower": 0,
      "txGain": 0,
      "rxGain": 0,
      "losses": 0,
      "frequency": 2440,
      "pathLossModel": 2,
      "distance": 10,
      "sensitivityOverride": 0,
      "extraLossCount": 0,
      "extraLoss1": 0,
      "extraLoss2": 0,
      "extraLoss3": 0,
      "extraLoss4": 0,
      "extraLoss5": 0,
      "extraLoss6": 0
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": [
    {
      "type": "float_parsing",
      "loc": [
        "body",
        "inputs",
        "phy"
      ],
      "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 pageBLE Link Budget & Range Calculator — Bluetooth Low Energy by PHY, at these values