RT60 calculator: how long does sound ring in your room?
RT60 is the time it takes a sound to die away by 60 dB after it stops. Too long and speech blurs and music turns muddy; too short and a room feels dead. This RT60 calculator estimates the reverberation time of a room from its dimensions and surfaces, octave band by octave band from 125 Hz to 4 kHz, using both the Sabine and the Eyring formulas.
Pick materials from a table of generic absorption coefficients, add windows, rugs, curtains, sofas or acoustic panels, and compare the result with a target RT60 for the room’s use: a home cinema, a studio control room, a classroom or a concert hall. It runs in your browser in metres or feet.
How to use the RT60 Calculator
- Enter the room’s length, width and height.
- Choose the floor, ceiling and wall materials.
- Add up to four items such as windows, rugs, curtains, seats or panels, with their area and where they sit.
- Choose the room’s use and read the RT60, the target and how much absorption to add.
RT60 Calculator features
Sabine and Eyring
Both classic formulas, by octave band and as a mid-frequency average.
Materials table
24 common surfaces with coefficients from 125 Hz to 4 kHz.
Targets by use
ITU-R BS.1116 listening rooms, ANSI S12.60 and BB93 classrooms, and rules of thumb for homes and halls.
Treatment estimate
How many square metres of absorption bring a live room to target.
Chart and tables
RT60 by band against the target range, plus each surface’s share of the absorption.
Formulas and a worked example
Sabine: RT60 = 0.161 × V ÷ A, where V is the volume in m³ and A the total absorption in m² sabins: each surface’s area times its absorption coefficient α. In feet the constant is 0.049. Eyring: RT60 = 0.161 × V ÷ (−S × ln(1 − ᾱ)), with S the total surface and ᾱ the average coefficient; it is more accurate for well-damped rooms, where Sabine reads high.
Example: a bare 10 × 10 × 10 m concrete room (α 0.02 at 1 kHz) has A = 600 × 0.02 = 12 m² sabins, so RT60 = 0.161 × 1000 ÷ 12 = 13.4 s. Covering half the walls with 50 mm mineral wool (α ≈ 0.99) adds about 194 m² sabins (198 minus the 4 the concrete gave) and drops it to about 0.8 s.
What is a good RT60?
| Room | Target RT60 (mid frequencies) | Source |
|---|---|---|
| Critical listening room, control room | 0.25 × (V ÷ 100 m³)^⅓ s, about 0.2–0.3 s | ITU-R BS.1116-3 |
| Classroom, US | ≤ 0.6 s up to 283 m³; ≤ 0.7 s to 566 m³ | ANSI/ASA S12.60-1 |
| Classroom, UK new build | ≤ 0.6 s primary; ≤ 0.8 s secondary | BB93 (2015) |
| Home cinema, hi-fi room | 0.3–0.5 s | rule of thumb |
| Meeting room, office | 0.4–0.8 s | rule of thumb |
| Concert hall | 1.8–2.2 s occupied | rule of thumb |
About the absorption coefficients
The materials table is a generic set compiled from public tables (sengpielaudio’s absorption-coefficient table, the Wikipedia table after Parker’s Good Vibrations (2009), and av-info.eu’s typical values); where sources overlap they agree closely. Real products, thicknesses and mounting depths differ, so treat the result as an estimate within about 10–20%. Absorbent panels work best at mid and high frequencies; bass needs thick or tuned traps, and below the room’s Schroeder frequency the room mode calculator describes the sound better than RT60.
Sabine assumes a diffuse sound field. In rooms with all the absorption on one surface, such as a carpeted floor and hard walls, the real decay can be longer than either formula predicts. To hear the effect of reverb on a recording, try add reverb to audio.
RT60 Calculator FAQ
What is a good RT60 time?
About 0.2–0.3 s for a studio control room, 0.3–0.5 s for a home cinema, 0.6–0.8 s or less for classrooms and around 2 s for an orchestral concert hall. This RT60 calculator shows the target for the use you choose.
How do I calculate RT60?
With Sabine’s formula, RT60 = 0.161 × volume ÷ total absorption (m² sabins). Total absorption is the sum of each surface’s area times its absorption coefficient.
What is the difference between Sabine and Eyring?
Sabine is simple and accurate for live rooms. Eyring accounts for high average absorption and gives shorter, more realistic times in well-treated rooms.
Why does RT60 change with frequency?
Materials absorb different amounts at different frequencies. Carpet and foam absorb treble but little bass, while thin panels and windows absorb some bass.
How many acoustic panels do I need?
Find the extra absorption the calculator suggests and divide by the panel’s coefficient times its area. A 1.2 × 0.6 m mineral-wool panel adds about 0.7 m² sabins at mid frequencies.
Does furniture affect reverberation time?
Yes. Sofas, beds, bookshelves and people absorb sound; add them as items with an approximate area.