Documentation sections

RT60 Reverberation Time Calculator

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

Slug rt60-reverberation. Calculate room reverberation time (RT60) using Sabine and Eyring equations. Enter dimensions and average absorption coefficient to get decay time, critical distance, and Schroeder frequency for acoustic treatment design.

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 rt60-reverberation
Name	Unit	Range	Default	Description
lengthnumber	m	1 … 100	6	Room Length
widthnumber	m	1 … 100	4	Room Width
heightnumber	m	1.5 … 30	3	Room Height
avgAbsorptionnumber	none	0.01 … 0.99	0.2	Bare concrete ~0.03, carpet ~0.3, acoustic panels ~0.8. With surfaces listed, the coefficient of the rest of the room.
numSurfacesnumber	none	0 … 8	0	Surfaces with their own absorption, such as a carpet, panels or curtains; the rest of the room keeps the average coefficient (0–8)
surface1Areanumber	m²	0 … 10000	10	Area of listed surface 1, part of the room's surface
surface1Alphanumber	none	0 … 0.99	0.3	Absorption coefficient of listed surface 1 at mid frequencies (500 Hz–1 kHz)
surface2Areanumber	m²	0 … 10000	10	Area of listed surface 2, part of the room's surface
surface2Alphanumber	none	0 … 0.99	0.3	Absorption coefficient of listed surface 2 at mid frequencies (500 Hz–1 kHz)
surface3Areanumber	m²	0 … 10000	10	Area of listed surface 3, part of the room's surface
surface3Alphanumber	none	0 … 0.99	0.3	Absorption coefficient of listed surface 3 at mid frequencies (500 Hz–1 kHz)
surface4Areanumber	m²	0 … 10000	10	Area of listed surface 4, part of the room's surface
surface4Alphanumber	none	0 … 0.99	0.3	Absorption coefficient of listed surface 4 at mid frequencies (500 Hz–1 kHz)
surface5Areanumber	m²	0 … 10000	10	Area of listed surface 5, part of the room's surface
surface5Alphanumber	none	0 … 0.99	0.3	Absorption coefficient of listed surface 5 at mid frequencies (500 Hz–1 kHz)
surface6Areanumber	m²	0 … 10000	10	Area of listed surface 6, part of the room's surface
surface6Alphanumber	none	0 … 0.99	0.3	Absorption coefficient of listed surface 6 at mid frequencies (500 Hz–1 kHz)
surface7Areanumber	m²	0 … 10000	10	Area of listed surface 7, part of the room's surface
surface7Alphanumber	none	0 … 0.99	0.3	Absorption coefficient of listed surface 7 at mid frequencies (500 Hz–1 kHz)
surface8Areanumber	m²	0 … 10000	10	Area of listed surface 8, part of the room's surface
surface8Alphanumber	none	0 … 0.99	0.3	Absorption coefficient of listed surface 8 at mid frequencies (500 Hz–1 kHz)

Outputs

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

Outputs of rt60-reverberation
Field	Unit	Description
rt60Sabineheadline	s	RT60 (Sabine)
rt60Eyring	s	RT60 (Eyring)
criticalDistance	m	Critical Distance
schroederFreq	Hz	Schroeder Frequency
totalAbsorption	sabins	Total Absorption
volume	m³	Room Volume
surfaceArea	m²	Surface Area
optimalSpeech	s	Optimal RT60 (Speech)
optimalMusic	s	Optimal RT60 (Music)
otherArea	m²	The room’s surface not listed, at the average absorption coefficient
meanAbsorption	none	Total absorption over the room’s surface, A/S: the coefficient the Eyring equation takes

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": "rt60-reverberation",
    "inputs": {
      "length": 6,
      "width": 4,
      "height": 3,
      "avgAbsorption": 0.2,
      "numSurfaces": 0,
      "surface1Area": 10,
      "surface1Alpha": 0.3,
      "surface2Area": 10,
      "surface2Alpha": 0.3,
      "surface3Area": 10,
      "surface3Alpha": 0.3,
      "surface4Area": 10,
      "surface4Alpha": 0.3,
      "surface5Area": 10,
      "surface5Alpha": 0.3,
      "surface6Area": 10,
      "surface6Alpha": 0.3,
      "surface7Area": 10,
      "surface7Alpha": 0.3,
      "surface8Area": 10,
      "surface8Alpha": 0.3
    }
  }'

import rftools

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

result = client.calculate("rt60-reverberation", {
    "length": 6,
    "width": 4,
    "height": 3,
    "avgAbsorption": 0.2,
    "numSurfaces": 0,
    "surface1Area": 10,
    "surface1Alpha": 0.3,
    "surface2Area": 10,
    "surface2Alpha": 0.3,
    "surface3Area": 10,
    "surface3Alpha": 0.3,
    "surface4Area": 10,
    "surface4Alpha": 0.3,
    "surface5Area": 10,
    "surface5Alpha": 0.3,
    "surface6Area": 10,
    "surface6Alpha": 0.3,
    "surface7Area": 10,
    "surface7Alpha": 0.3,
    "surface8Area": 10,
    "surface8Alpha": 0.3,
})
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": "rt60-reverberation",
    "inputs": {
      "length": 6,
      "width": 4,
      "height": 3,
      "avgAbsorption": 0.2,
      "numSurfaces": 0,
      "surface1Area": 10,
      "surface1Alpha": 0.3,
      "surface2Area": 10,
      "surface2Alpha": 0.3,
      "surface3Area": 10,
      "surface3Alpha": 0.3,
      "surface4Area": 10,
      "surface4Alpha": 0.3,
      "surface5Area": 10,
      "surface5Alpha": 0.3,
      "surface6Area": 10,
      "surface6Alpha": 0.3,
      "surface7Area": 10,
      "surface7Alpha": 0.3,
      "surface8Area": 10,
      "surface8Alpha": 0.3
    }
  }),
});
console.log(response.status, await response.json());

package main

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

func main() {
	body := []byte(`{
	  "slug": "rt60-reverberation",
	  "inputs": {
	    "length": 6,
	    "width": 4,
	    "height": 3,
	    "avgAbsorption": 0.2,
	    "numSurfaces": 0,
	    "surface1Area": 10,
	    "surface1Alpha": 0.3,
	    "surface2Area": 10,
	    "surface2Alpha": 0.3,
	    "surface3Area": 10,
	    "surface3Alpha": 0.3,
	    "surface4Area": 10,
	    "surface4Alpha": 0.3,
	    "surface5Area": 10,
	    "surface5Alpha": 0.3,
	    "surface6Area": 10,
	    "surface6Alpha": 0.3,
	    "surface7Area": 10,
	    "surface7Alpha": 0.3,
	    "surface8Area": 10,
	    "surface8Alpha": 0.3
	  }
	}`)
	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": "rt60-reverberation",
  "values": {
    "volume": 72,
    "surfaceArea": 108,
    "totalAbsorption": 21.6,
    "rt60Sabine": 0.5366666666666666,
    "rt60Eyring": 0.4810057593024351,
    "schroederFreq": 172.66966964355612,
    "criticalDistance": 0.6602201778420694,
    "optimalSpeech": 0.6243463988580059,
    "optimalMusic": 1.2143994978587611,
    "otherArea": 108,
    "meanAbsorption": 0.2
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:rt60-reverberation",
    "version": "api@3f2c1a9b04de",
    "formulaRef": null,
    "assumptions": [],
    "validRange": {
      "status": "inside",
      "bounds": {
        "length": {
          "min": 1,
          "max": 100,
          "unit": "m"
        },
        "width": {
          "min": 1,
          "max": 100,
          "unit": "m"
        },
        "height": {
          "min": 1.5,
          "max": 30,
          "unit": "m"
        },
        "avgAbsorption": {
          "min": 0.01,
          "max": 0.99,
          "unit": ""
        },
        "numSurfaces": {
          "min": 0,
          "max": 8,
          "unit": ""
        },
        "surface1Area": {
          "min": 0,
          "max": 10000,
          "unit": "m²"
        },
        "surface1Alpha": {
          "min": 0,
          "max": 0.99,
          "unit": ""
        },
        "surface2Area": {
          "min": 0,
          "max": 10000,
          "unit": "m²"
        },
        "surface2Alpha": {
          "min": 0,
          "max": 0.99,
          "unit": ""
        },
        "surface3Area": {
          "min": 0,
          "max": 10000,
          "unit": "m²"
        },
        "surface3Alpha": {
          "min": 0,
          "max": 0.99,
          "unit": ""
        },
        "surface4Area": {
          "min": 0,
          "max": 10000,
          "unit": "m²"
        },
        "surface4Alpha": {
          "min": 0,
          "max": 0.99,
          "unit": ""
        },
        "surface5Area": {
          "min": 0,
          "max": 10000,
          "unit": "m²"
        },
        "surface5Alpha": {
          "min": 0,
          "max": 0.99,
          "unit": ""
        },
        "surface6Area": {
          "min": 0,
          "max": 10000,
          "unit": "m²"
        },
        "surface6Alpha": {
          "min": 0,
          "max": 0.99,
          "unit": ""
        },
        "surface7Area": {
          "min": 0,
          "max": 10000,
          "unit": "m²"
        },
        "surface7Alpha": {
          "min": 0,
          "max": 0.99,
          "unit": ""
        },
        "surface8Area": {
          "min": 0,
          "max": 10000,
          "unit": "m²"
        },
        "surface8Alpha": {
          "min": 0,
          "max": 0.99,
          "unit": ""
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "length": 6,
      "width": 4,
      "height": 3,
      "avgAbsorption": 0.2,
      "numSurfaces": 0,
      "surface1Area": 10,
      "surface1Alpha": 0.3,
      "surface2Area": 10,
      "surface2Alpha": 0.3,
      "surface3Area": 10,
      "surface3Alpha": 0.3,
      "surface4Area": 10,
      "surface4Alpha": 0.3,
      "surface5Area": 10,
      "surface5Alpha": 0.3,
      "surface6Area": 10,
      "surface6Alpha": 0.3,
      "surface7Area": 10,
      "surface7Alpha": 0.3,
      "surface8Area": 10,
      "surface8Alpha": 0.3
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": [
    {
      "type": "float_parsing",
      "loc": [
        "body",
        "inputs",
        "length"
      ],
      "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 pageRT60 Reverberation Time Calculator, at these values