Reverberation Time Calculator
Reverberation time (RT60) describes how long it takes for sound to decay by 60 dB in a room after the source is switched off. It is the single most important acoustic parameter for room design: recording studios aim for 0.2-0.4 s, lecture theatres for 0.5-0.8 s, and concert halls for 1.5-2.5 s. Sabine's formula RT60 = 0.161 V / A relates RT60 to the room volume V in cubic metres and the total absorption A in sabins. Total absorption is the sum of each surface's area multiplied by its absorption coefficient. Use this calculator for initial room design or treatment estimates.
Sabine's formula
RT60 = 0.161 × V / A
Where V is the room volume in m^3 and A is the total absorption in sabins (m^2). The constant 0.161 s/m is derived from the speed of sound in air (approximately 343 m/s at 20 degrees C) and the logarithmic decay constant.
Recommended RT60 by application
- Recording studio / vocal booth: 0.2-0.4 s
- Home cinema: 0.3-0.5 s
- Conference room: 0.4-0.6 s
- Lecture theatre: 0.5-0.8 s
- House of worship: 0.8-1.5 s
- Symphony concert hall: 1.5-2.5 s
Frequently asked questions
What is RT60?
RT60 (reverberation time) is the time it takes for sound in a room to decay by 60 dB after the source stops. It is the primary descriptor of a room's acoustic character: speech requires short RT60 (0.3-0.8 s), concert halls prefer longer values (1.5-2.5 s).
What is Sabine's formula?
RT60 = 0.161 V / A, where V is the room volume in cubic metres and A is the total absorption in sabins (square metres). The constant 0.161 incorporates the speed of sound in air at room temperature. This formula was derived empirically by Wallace Clement Sabine around 1900.
What is a sabin?
A sabin is the unit of sound absorption. One sabin equals the absorption of one square metre of a perfectly absorbing surface (absorption coefficient = 1.0). Total absorption A is the sum of each surface area multiplied by its absorption coefficient.
How do I find absorption coefficients?
Absorption coefficients are measured and published by manufacturers, or from databases such as the Noise Control Engineering journal or AES publications. Typical values: carpet 0.3-0.6, concrete 0.02, acoustic ceiling tile 0.7-0.9.
What are the limitations of Sabine's formula?
Sabine's formula assumes a diffuse, reverberant field and becomes inaccurate for rooms with very high absorption (A approaches V). The Eyring formula is more accurate in highly damped rooms: RT60 = -0.161 V / (S ln(1 - alpha_avg)).
Official sources
- Audio Engineering Society (AES): aes.org.
- ANSI/ASA S12.60: Acoustical Performance Criteria for Schools (references Sabine formula).
- OpenStax University Physics Vol. 1, Chapter 17: Sound.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.