Calculate the RT60 reverberation time of a room using Sabine's formula for architectural acoustics.
Last updated: March 2026 | By ForgeCalc Engineering
Reverberation time (RT60) is the time required for the sound pressure level in a room to decrease by 60 decibels (dB) after the sound source has stopped. It is a key metric in architectural acoustics used to determine the "liveliness" or "deadness" of a space.
A long reverberation time (like in a cathedral) makes speech difficult to understand but can enhance music. A short reverberation time (like in a recording studio) provides clarity but can feel "unnatural" or "dry." Sabine's formula is the most common method for estimating this time based on room volume and absorption.
Where:
• RT60 is the reverberation time in seconds
• V is the room volume in m³
• A is the total absorption in Sabins (S × α)
• S is the total surface area in m²
• α is the average absorption coefficient
Typically between 0.4 and 0.6 seconds. This provides a balance of clarity for speech and warmth for music.
60 dB represents a reduction in sound energy by a factor of one million (10⁶). It was chosen because it roughly corresponds to the decay from a loud sound to inaudibility in a quiet room.
It's a value between 0 and 1 that represents the fraction of sound energy absorbed by a material. 0 means total reflection (like a mirror), and 1 means total absorption (like an open window).
Yes. Most materials absorb sound differently at different frequencies. RT60 is usually measured at 500 Hz or 1000 Hz for general reporting, but full acoustical analysis looks at multiple octaves.
Related Tools
Calculate acoustic impedance.
Calculate signal attenuation.
Calculate beat frequency.
Calculate Bragg's Law.
Calculate critical damping.
Calculate damping ratio.