Room Absorption Area Calculator
A room's total sound absorption, measured in sabins, sets how quickly sound decays and how much reverberation a space has. It is the sum of every surface's area multiplied by its absorption coefficient. This calculator takes the total surface area, an average absorption coefficient, and the room volume to compute the absorption in sabins and the Sabine reverberation time RT60. Use it to size acoustic treatment, predict how live or dead a room will sound, and check whether a space meets a target reverberation time for speech or music.
Absorption and reverberation formula
Total absorption A = S * a (metric sabins)
RT60 = 0.161 * V / A (seconds)
(V in m3, A in metric sabins)
For detailed work, sum each surface's area times its own coefficient. The single average coefficient gives a quick whole-room estimate.
Reverberation context
- RT60 is the time for sound to decay by 60 dB after the source stops.
- Hard surfaces (concrete, glass) have very low coefficients near 0.02.
- Thick acoustic panels can exceed 0.9 absorption at mid frequencies.
- Doubling total sabins roughly halves the reverberation time.
- Speech clarity favors short RT60; concert halls use longer times.
Room absorption: frequently asked questions
What is total absorption area (sabins)?
Total absorption is the sum over all room surfaces of each surface area times its absorption coefficient: A = sum of S_i * a_i. The result is expressed in sabins (metric sabins are square meters of equivalent perfect absorber). It quantifies how much sound energy the room removes per reflection and is the key input to Sabine reverberation time.
What is the Sabine reverberation time formula?
Reverberation time RT60 = 0.161 * V / A in metric units, where V is room volume in cubic meters and A is total absorption in metric sabins. RT60 is the time for sound to decay by 60 dB after the source stops. The constant 0.161 comes from the speed of sound and the geometry of a diffuse field.
What is an absorption coefficient?
An absorption coefficient a is the fraction of incident sound energy a material absorbs rather than reflects, from 0 (perfectly reflective) to 1 (perfectly absorptive). It is frequency dependent and is measured in a reverberation chamber per standards such as ASTM C423. Hard surfaces such as concrete are near 0.02; thick acoustic panels can exceed 0.9 at mid frequencies.
Why use an average absorption coefficient?
When a room has many surfaces, designers often compute an area-weighted average coefficient. This calculator uses a single average coefficient times the total surface area for a quick estimate. For detailed design, sum each surface separately because coefficients vary widely by material and frequency.
How do I lower a room's reverberation time?
Add absorption: increase the total sabins by installing absorptive materials such as panels, carpet, curtains or ceiling tiles. Because RT60 is inversely proportional to absorption, doubling the total sabins roughly halves the reverberation time. Larger rooms need proportionally more absorption to reach the same RT60.
Official sources
- ASTM International: Standards including C423 sound absorption.
- NIST: National Institute of Standards and Technology.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.