Room Reverb Time (RT60) Calculator
Calculate the reverberation time of a room based on dimensions and surface materials.
Optimize acoustics for music or recording.
Room Reverberation Time (RT60) is the time it takes for sound to decay by 60 decibels after the source stops. It is the most important measurement in room acoustics.
The Sabine equation:
RT60 = 0.161 × V / A
Where:
- V = room volume in cubic meters
- A = total sound absorption in sabins (m²)
- 0.161 = a constant derived from the speed of sound
Imperial version:
RT60 = 0.049 × V / A
Where V is in cubic feet and A is in sabins (ft²).
How absorption is calculated:
A = Σ (Surface Area × Absorption Coefficient)
Each surface material absorbs a different fraction of sound energy:
Common absorption coefficients (at 500 Hz):
- Concrete/brick: 0.02 (highly reflective)
- Drywall (gypsum): 0.05
- Glass (window): 0.04
- Wood floor: 0.10
- Tile floor: 0.02
- Carpet (thick): 0.30
- Carpet (thin): 0.15
- Curtains (heavy): 0.50
- Acoustic foam (2 inch): 0.60
- Fiberglass panel (4 inch): 0.90
- Upholstered furniture: 0.50-0.70
Ideal RT60 by room purpose:
- Recording studio (control room): 0.3-0.5 seconds
- Home theater: 0.4-0.6 seconds
- Conference room: 0.5-0.7 seconds
- Classroom: 0.6-0.8 seconds
- Concert hall: 1.5-2.5 seconds
- Church/cathedral: 2.0-5.0+ seconds
- Living room: 0.4-0.8 seconds
If your RT60 is too high (too reverberant): Add absorption materials — acoustic panels, carpets, curtains, soft furniture.
If your RT60 is too low (too dead): Remove some absorption or add reflective surfaces. Some reverb is needed for natural-sounding speech and music.
The Sabine equation works best for rooms with relatively uniform absorption distribution. For rooms with one very absorptive surface and others very reflective, the Eyring equation provides more accurate results.