RT60 Reverberation Time Calculator
This page does a different job from the rest of the site. It is about room acoustics — how long sound physically rings in a real room — not about tempo-synced effect settings for a mix.
Controlled studio range
| Surface | Area | α (500 Hz) | Absorption |
|---|---|---|---|
| CeilingAcoustic ceiling tile | 20 m² | 0.7 | 14 |
| FloorCarpet, heavy on pad | 20 m² | 0.3 | 6 |
| WallsGypsum drywall | 54 m² | 0.1 | 5.4 |
How RT60 works: Sabine and Eyring
Start with the honest distinction. The other tools on this site, including the combined reverb calculator on the home page, set the reverb time of an effect in a mix, synced to a song tempo. RT60 measures something else entirely: the time, in seconds, for sound in a physical room to decay by 60 dB after the source stops. It describes your studio, your hall, or your living room — not a plugin setting.
Two classic formulas estimate it. The Sabine formula divides the room volume by its total absorption. The Eyring formula refines the same idea and behaves better in dead, heavily treated rooms. Both are given here in metric form; in imperial units, with volume in cubic feet and absorption in square-foot sabins, the constant 0.161 becomes 0.049 in both formulas.
Volume V is the room volume in cubic meters. S is the total surface area of the room in square meters. A is the total absorption in sabins, built by adding up every surface: A = Σ (surface area × α), where α is that material's absorption coefficient. This calculator uses coefficients at 500 Hz, a standard single reference frequency for a first estimate. Each person in the room also adds 0.45 sabins directly to A. The full reasoning behind using both formulas, and where they come from, is set out on the methodology page.
| Material | Absorption coefficient α at 500 Hz |
|---|---|
| Smooth concrete | 0.03 |
| Painted brick | 0.05 |
| Glass (windows) | 0.05 |
| Gypsum drywall | 0.10 |
| Wood floor | 0.10 |
| Carpet (heavy, on pad) | 0.30 |
| Heavy curtains | 0.50 |
| Acoustic ceiling tile | 0.70 |
Read the coefficients as “how much of the sound hitting this surface is absorbed rather than reflected.” Bare concrete at 0.03 reflects almost everything, which is why an empty concrete room rings for so long. Acoustic ceiling tile at 0.70 absorbs most of what reaches it. Most real rooms are mixtures, which is exactly why A is a sum over every surface rather than a single material choice.
Worked example: a 5 × 4 × 3 meter room
Take a room 5 m long, 4 m wide, and 3 m high. Its volume is 5 × 4 × 3 = 60 cubic meters. Its total surface area is 2 × (20 + 15 + 12) = 94 square meters. Suppose the surfaces and contents add up to a total absorption A of 12 sabins.
The two answers are close here — 0.805 s from Sabine and about 0.752 s from Eyring — because this room is only moderately absorptive. The gap widens as a room gets deader. As a rule-of-thumb reading, 0.805 s falls in the 0.6–1.0 s band described below: a live room, pleasant for recording acoustic instruments, but livelier than most people want for critical mixing or clear speech recording.
| RT60 | Rule-of-thumb reading |
|---|---|
| Under 0.3 s | Very dry — voice booth territory |
| 0.3–0.6 s | Controlled studio |
| 0.6–1.0 s | Live room |
| 1.0–1.8 s | Hall-like |
| Over 1.8 s | Cathedral territory — speech gets muddy |
These bands are rules of thumb, not standards. A podcast room, a drum room, and a choir rehearsal space can all be “good” at very different RT60 values, because the right amount of ring depends on what the room is for.
Practical guidance for treating a room
Change the biggest surface first
Absorption is area times coefficient, so the largest surface usually offers the largest improvement for the least effort. In many home studios that surface is the ceiling or a long bare wall. Covering a small patch of an already-treated wall while a huge drywall ceiling stays bare will move A very little. Run the numbers both ways in the calculator before buying anything: swap one surface at a time and watch which change actually moves the RT60.
Treating a home studio
For a typical small home studio, the controlled-studio band of 0.3–0.6 s is a sensible target for recording and mixing. Heavy carpet on the floor (0.30), heavy curtains over windows (0.50 in place of glass at 0.05), and acoustic treatment on the ceiling (tile at 0.70 in place of drywall at 0.10) are the highest-leverage changes in the coefficient table, precisely because floors, windows, and ceilings are large areas. Do not chase the driest possible number: an over-treated, under-0.3 s room feels unnatural to perform in, and performers give worse takes in rooms that sound dead.
Do not confuse this with the room reverb effect
A short, tempo-synced room effect in a mix is a different thing from the acoustics on this page, despite the similar name. If you are setting a plugin to imitate a small space inside a song, use the room reverb calculator instead, which works in milliseconds against your BPM. Use this RT60 page when the question is about a physical room you can stand in, measure, and treat.
Limitations
This is a single-frequency estimate. All coefficients here are at 500 Hz, but real materials absorb bass, midrange, and treble very differently — heavy curtains that tame the midrange do little to low frequencies — so a room's true RT60 varies by frequency band. Treat the result as a good overall estimate, not a frequency-by-frequency analysis.
Furniture, irregular shapes, and diffusion are not modeled. Bookshelves, sofas, angled surfaces, and scattering objects change how sound behaves in ways a surface-area sum cannot capture, and two rooms with identical dimensions and materials can still measure differently. Finally, the Sabine formula overestimates RT60 in dead rooms, because it assumes reflections keep circulating in a way that heavy absorption prevents; in a very treated room, trust the Eyring result more. For a decision that costs real money, confirm the estimate with an actual measurement in the room.
Frequently asked questions
What does RT60 mean?
RT60 is the time, in seconds, for sound in a room to decay by 60 dB after the source stops. It is a property of a physical space — its volume, surfaces, and contents — not an effect setting. A small treated studio might measure around 0.4 s, while a large bare hall can ring for well over 1.8 s.
Should I use the Sabine or the Eyring formula?
Use both and compare them. In live or moderately treated rooms the two agree closely, as in the worked example on this page: 0.805 s versus about 0.752 s. In dead, heavily absorptive rooms Sabine overestimates, and the Eyring result is the more trustworthy of the two.
What is a good RT60 for a home studio?
As a rule of thumb, 0.3–0.6 s reads as a controlled studio: dry enough for clear recordings and reliable mixing decisions, without feeling unnaturally dead. Under 0.3 s suits a voice booth. Above 0.6 s the room starts to sound live, which can flatter acoustic instruments but smears speech and monitoring accuracy.
How do people in the room affect RT60?
Each person adds 0.45 sabins directly to the total absorption A. In a small room that is a noticeable change: a few people can pull the RT60 down on their own, which is one reason an empty rehearsal room sounds livelier than the same room during a session. Add the occupants you expect before judging a result.
Is RT60 the same as the reverb time on my plugin?
No. Plugin reverb time is a tempo-synced effect setting inside a mix, usually in milliseconds. RT60 is the measured or estimated decay of a real room, in seconds. They share a name and a concept, but you set one with your BPM and the other by treating physical surfaces — this page covers the room, and the other tools on this site cover the effect.
- Engineering ToolBox — Sound Absorption Coefficients — Source of the 500 Hz absorption coefficient table used on this page.
- Wikipedia — Reverberation — Background on RT60, and the Sabine and Eyring formulas.