Reverb RT60 Calculator
RT60 is the headline number for room acoustics: how long it takes a sound to fade by 60 decibels once the source stops. The Sabine equation gives a quick estimate from three figures, the room volume, its total interior surface area, and the average sound absorption coefficient of those surfaces. Enter your room dimensions in metric units and an average absorption coefficient, and this calculator returns the estimated RT60 in seconds along with the total absorption in metric sabins. Use it to plan acoustic treatment before measuring.
Sabine RT60 formula
A = surface area * average coefficient (metric sabins)
RT60 = 0.161 * V / A
V = room volume in cubic metres
The constant 0.161 s/m applies in metric units (use 0.049 for cubic feet and square feet). A is the total absorption: increase surface area or the average coefficient to shorten RT60.
Typical RT60 targets
- Recording control room or vocal booth: about 0.2 to 0.4 seconds.
- Home listening or small studio: about 0.3 to 0.6 seconds.
- Classroom or conference room: about 0.6 to 0.8 seconds for speech clarity.
- Concert hall (orchestral): about 1.8 to 2.2 seconds.
- Cathedral or large reverberant space: 3 seconds or more.
RT60 reverberation: frequently asked questions
What is RT60?
RT60 is the reverberation time of a room: the time, in seconds, for a sound to decay by 60 decibels after the source stops. It is the standard single-number measure of how live or dead a room sounds. Concert halls target around 1.5 to 2.5 seconds, while recording control rooms aim for roughly 0.2 to 0.4 seconds.
What is the Sabine equation?
The Sabine equation estimates RT60 as 0.161 times the room volume in cubic metres, divided by the total absorption in metric sabins. Total absorption is the surface area in square metres multiplied by the average absorption coefficient. The constant 0.161 s/m comes from the speed of sound in air at room temperature.
What is an absorption coefficient?
An absorption coefficient is a number from 0 to 1 describing how much sound energy a surface absorbs: 0 is perfectly reflective and 1 is perfectly absorptive (an open window). Bare concrete or glass is around 0.02 to 0.05; heavy carpet and acoustic panels can exceed 0.6. Coefficients vary with frequency, so RT60 is usually quoted per octave band. Enter the average for your room.
What are the limits of the Sabine equation?
Sabine assumes a diffuse sound field and works best when absorption is low to moderate and spread evenly. In very dead rooms (high average coefficient) it overestimates RT60, and the Eyring equation is more accurate. Treat this calculator as a fast design estimate, not a substitute for measurement.
Sources and definitions
- The Sabine reverberation equation (RT60 = 0.161 V / A in metric units) is the foundational result of architectural acoustics, established by Wallace Clement Sabine.
- National Institute of Standards and Technology: SI units reference (length in metres, time in seconds).
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.