Case 1
- Room volume
- 200m³
- Total surface area
- 240m²
- Average absorption coefficient α
- 0.2
0.67s
Open with these valuesReverberation Time Calculator
0.67s
Result: 0.67 sRT60 is the time a sound takes to fade by 60 dB after the source stops. Sabine's formula divides 0.161 times the room volume by the total absorption, which is the surface area times the average absorption coefficient. Metres and square metres — the constant 0.161 only holds for them.
Worked examples
Case 2
- Room volume
- 50m³
- Total surface area
- 80m²
- Average absorption coefficient α
- 0.1
1.01s
Open with these valuesCase 3
- Room volume
- 1000m³
- Total surface area
- 650m²
- Average absorption coefficient α
- 0.25
0.99s
Open with these valuesHow it's calculated
RT60 = 0.161 × V ÷ (S × α)
- StepEnter the room volume in cubic metres — length × width × height.
- StepAdd up walls, floor and ceiling for the total surface area.
- StepEstimate one average absorption coefficient for all of it, 0 to 1.
- ResultRead RT60; aim for 0.3–0.6 s for speech, 1.5–2.5 s for music.
Reference table
| Volume, surface, α | Room | RT60 (s) |
|---|---|---|
| 50, 80, 0.1 | Small bare room, hard surfaces | 1.01 |
| 100, 150, 0.15 | Living room, sparsely furnished | 0.72 |
| 200, 240, 0.2 | Classroom, some absorption | 0.67 |
| 500, 400, 0.3 | Treated meeting hall | 0.67 |
| 1000, 650, 0.25 | Small auditorium | 0.99 |
| 300, 300, 1 | Fully absorbing room, the lower bound | 0.16 |
Questions
What is RT60 (reverberation time)?
RT60 is the time it takes for a sound to fade by 60 decibels — to about a thousandth of its energy — after the source stops. It is the standard measure of how live a room is: a long RT60 sounds echoey and boomy, a short one sounds tight and dead.
How do I calculate reverberation time with the Sabine formula?
Divide 0.161 times the room volume by the total absorption: RT60 = 0.161 × V / (S × α). For a 200 m³ room with 240 m² of surface at an average coefficient α = 0.2, the absorption is 48 m² and RT60 = 0.161 × 200 / 48 ≈ 0.67 s.
What is a good reverberation time?
It depends on use: for clear speech in classrooms, offices, home theatres and podcast studios, aim for roughly 0.3 to 0.6 s. Concert halls and churches use longer times of about 1.5 to 2.5 s to blend and enrich music. There is no single right answer; match the RT60 to what the room is for.
What is the absorption coefficient α?
The absorption coefficient α describes how much sound a surface soaks up rather than reflects, from 0 (perfectly reflective, like polished concrete) to 1 (perfectly absorbing). Bare hard rooms average around 0.1; carpet, curtains, soft furniture, acoustic panels and people all raise it. The calculator uses a single average across the whole room.
How do I reduce reverberation in a room?
Add absorption. Because RT60 = 0.161 × V / A, raising the total absorption A lowers the reverberation time — roughly, doubling the average coefficient halves the RT60. Carpets, curtains, upholstered furniture, bookshelves and acoustic panels all help; people are excellent absorbers too, so a full room sounds tighter than an empty one.
Why 0.161, and does it work in feet?
No — 0.161 is the metric constant and only holds for cubic metres and square metres; the imperial version is 0.049. It is not a defined constant but an empirical one, derived as 24 × ln10 divided by the speed of sound at 20 °C, which gives about 0.1611.
Sources and last check
Information, not professional advice.