RT60 Calculator (Sabine + Eyring)
Estimate reverberation time (RT60) from room dimensions and absorption properties. Use Sabine for typical rooms and Eyring for more absorbent spaces.
What is reverberation time?
Reverberation time (usually written as RT60) is the time it takes for sound in a room to decay by 60 dB after the source stops. It is one of the most important acoustic indicators for speech clarity, music quality, and overall comfort.
If RT60 is too long, speech becomes muddy and music can sound boomy. If it is too short, rooms may feel acoustically “dead.” This calculator helps you estimate RT60 quickly so you can make informed treatment decisions.
How the calculator works
1) Sabine equation
The Sabine model is a classic approximation for many rooms:
- Metric: RT60 = 0.161 × V / A
- Imperial: RT60 = 0.049 × V / A
Where V is room volume and A is total equivalent absorption area (in sabins).
2) Eyring equation
The Eyring model can be more accurate when absorption is relatively high:
- Metric: RT60 = 0.161 × V / [−S × ln(1 − α)]
- Imperial: RT60 = 0.049 × V / [−S × ln(1 − α)]
Here S is total interior surface area, and α is average absorption coefficient.
How to use this reverberation time calculator
- Choose your unit system (metric or imperial).
- Enter room dimensions: length, width, and height.
- Select Sabine if you know total absorption area, or Eyring if you know average α.
- Click Calculate RT60 to get your estimate and quick interpretation.
Typical RT60 targets by room type
- Podcast booth / voice-over booth: 0.2 to 0.4 s
- Small office / meeting room: 0.4 to 0.7 s
- Classroom: 0.5 to 0.8 s
- Home theater: 0.3 to 0.6 s
- Small music rehearsal room: 0.6 to 1.0 s
- Concert hall (depends on genre): roughly 1.4 to 2.2 s
Target values vary with room volume, audience presence, and use case. Use these as starting points, not absolute rules.
What to do if your RT60 is too high or too low
If RT60 is too high (echoey room)
- Add broadband absorbers (walls/ceiling first-reflection zones).
- Use carpets, curtains, upholstered seating, and acoustic clouds.
- Consider bass traps for low-frequency buildup in small rooms.
If RT60 is too low (overdamped room)
- Reduce excessive absorption in some bands.
- Introduce diffusion to keep liveliness without obvious echoes.
- Balance the room by frequency instead of only adding/removing foam.
Practical notes for better estimates
- RT60 changes with frequency. Professional work uses octave-band values (125 Hz to 4 kHz or higher).
- Audience and furniture can significantly increase absorption.
- Irregular room geometry, openings, and coupled spaces reduce model accuracy.
- For design-grade results, verify with measurements (sine sweep, impulse response, ETC/RT curves).
Quick FAQ
Is lower RT60 always better?
No. Speech rooms usually need shorter RT60, while many music spaces benefit from longer decay for warmth and envelopment.
Which formula should I pick?
Use Sabine for quick estimates and moderate absorption. Use Eyring when average absorption is higher and you want a more conservative prediction.
Can this replace an on-site acoustic test?
Not completely. It is a planning tool. Final validation should come from in-room measurements.