Sabine RT60 Reverb Calculator
Reverberation time RT60 is the seconds a sound takes to fade by 60 decibels once the source stops, and it is the headline figure for how a room sounds. The Sabine equation estimates it from the room volume, the total surface area, and the area-weighted average absorption coefficient of the surfaces. This calculator applies the metric Sabine formula with its derived 0.161 constant. Absorption coefficient is a user input because it depends on your materials, which manufacturers publish per frequency band.
Sabine equation
total absorption A = surface area * average coefficient
RT60 = 0.161 * volume / A
RT60 (ms) = RT60 * 1000
0.161 = 24 * ln(10) / 343 (speed of sound)
The 0.161 constant comes from the speed of sound and the 60 dB decay definition. Higher volume lengthens RT60; more absorption shortens it. Total absorption A is measured in metric sabins.
Reverberation facts
- Speech intelligibility usually wants a short RT60, often well under 1 second in classrooms.
- Concert halls are designed for longer RT60 values to add warmth.
- Doubling absorption halves RT60; doubling volume doubles it.
- Sabine assumes a diffuse field and is most accurate at moderate absorption.
- Absorption coefficients are frequency dependent, so RT60 differs per band.
RT60: frequently asked questions
What is RT60?
RT60 is the reverberation time: the seconds it takes for sound in a room to decay by 60 decibels after the source stops. It is the standard single-number measure of how live or dead a room sounds, defined in ISO 3382.
What is the Sabine equation?
The Sabine equation states RT60 = 0.161 times room volume divided by total absorption, in metric units. Total absorption is the surface area times the average absorption coefficient, measured in metric sabins. The 0.161 constant follows from the speed of sound.
Where does the 0.161 constant come from?
It equals 24 times the natural log of 10 divided by the speed of sound (about 343 m/s at room temperature), which works out to roughly 0.161 seconds per metre. It is a derived physical constant, not an estimate.
What absorption coefficient should I use?
Use the area-weighted average absorption coefficient of your surfaces, a value between 0 and 1, where 0 is fully reflective and 1 fully absorptive. It is a user input because it depends on your specific materials; manufacturers publish coefficients per frequency band.
When is the Sabine equation less accurate?
Sabine assumes a diffuse sound field and breaks down in very absorptive rooms or rooms with uneven absorption. For high average absorption the Eyring equation is more accurate. Use Sabine for typical rooms with moderate absorption.
Official sources
- International Organization for Standardization: ISO 3382 acoustics, measurement of reverberation time.
- Acoustical Society of America: architectural acoustics references.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.