This calculator uses the Sabine reverberation time estimate:
RT60 = k × V / A
- RT60 is reverberation time in seconds.
- V is room volume.
- A is total absorption in sabins.
- k is 0.161 (metric) or 0.049 (imperial).
Total absorption is computed from surfaces and extras:
A = Σ(Sᵢ × αᵢ) + Aₑₓₜᵣₐ
- Select a unit system that matches your dimensions.
- Enter room length, width, and height.
- Enter openings area for doors and windows.
- Choose materials, or type custom α values.
- Add people and extra absorption if needed.
- Click Calculate to view RT60 and details.
- Use CSV or PDF buttons to export results.
| Case | Dimensions (m) | Floor α | Ceiling α | Walls α | Openings area (m²) | Extras (sabins) | Estimated RT60 (s) |
|---|---|---|---|---|---|---|---|
| Speech room | 10 × 8 × 3 | 0.40 | 0.60 | 0.05 | 6 | People 10×0.50 + 8 | ~0.6 to 1.0 |
| Lively hall | 20 × 15 × 6 | 0.10 | 0.10 | 0.03 | 12 | 10 | ~1.6 to 2.4 |
| Treated studio | 6 × 5 × 2.7 | 0.40 | 0.60 | 0.10 | 2 | 25 | ~0.2 to 0.5 |
Example outputs are approximate and depend on chosen coefficients.
1) What RT60 represents
RT60 is the time for sound to decay about 60 dB after the source stops. Shorter RT60 improves speech clarity, while longer RT60 can add musical richness. Ideal values depend on room use and room volume.
2) Why the Sabine method is used
The Sabine estimate links room volume to total absorption under a diffuse-field assumption. It is popular for early-stage design because it is fast and easy to interpret. Very irregular rooms or heavy treatment may need more advanced modeling.
3) Key inputs that control the estimate
Volume grows with length, width, and height, so larger rooms tend to sound more reverberant unless absorption increases. Absorption is modeled as area times coefficient for each surface. Openings are separated so glass and curtains can differ from wall finishes.
4) Typical absorption coefficient ranges
Hard finishes are usually low absorption, often around 0.02 to 0.08 in mid frequencies. Carpet and heavy curtains can be higher, commonly 0.25 to 0.60. Acoustic ceiling tiles can reach about 0.50 to 0.80, reducing RT60 in many rooms. Coefficients vary with frequency and installation, so treat values as planning averages unless measured data is available.
5) People and furnishings as “extra” absorption
Occupied rooms are usually less reverberant than empty rooms. As a practical approximation, a seated person can contribute around 0.4 to 0.6 sabins in a speech-relevant band. Furniture and treatment can be entered as extra sabins for quick “what-if” checks.
6) Interpreting common target bands
Many speech-focused rooms aim for roughly 0.4 to 0.8 seconds. Classrooms and meeting rooms often work well near 0.6 to 1.0 seconds. Treated studios may target about 0.2 to 0.5 seconds, while some music venues may prefer 1.6 to 2.2 seconds. Larger auditoriums can tolerate longer times because reflections arrive later, but excessive RT60 can still reduce clarity without enough diffusion and absorption.
7) Unit systems and what changes
The method is the same, but the Sabine constant differs by unit system. This calculator uses 0.161 for metric inputs and 0.049 for imperial inputs. Keep all dimensions consistent with the selected system.
8) Practical next steps after an estimate
Use the result as a planning baseline: increase absorption to shorten RT60, or reduce absorption to lengthen it. For real projects, refine coefficients by frequency band, verify surface areas, and validate with in-room measurements once the space is built or treated.
1) What does RT60 mean in simple terms?
RT60 is how long echoes linger after a sound stops. It measures how quickly the room “dies out,” and it strongly influences clarity for speech and perceived spaciousness for music.
2) Why do I need absorption coefficients?
Coefficients describe how much sound energy a surface absorbs versus reflects. Multiplying surface area by its coefficient estimates how many sabins that surface contributes to the total absorption.
3) Which frequency does this estimate represent?
Sabine RT60 is frequency dependent, because materials change absorption with frequency. Use coefficients chosen for your target band, such as mid-frequency values often used for speech planning.
4) How do I include chairs, curtains, or acoustic panels?
Enter them as “Extra absorption (sabins)” if you know their equivalent absorption, or raise the relevant surface coefficient if the treatment covers a measured area, such as wall panels or curtains.
5) How should I set the openings area?
Add up the total area of doors and windows and enter it as openings. Then pick a material for openings, like glass or a curtain, to model their absorption separately from the wall finish.
6) Why can measured RT60 differ from the estimate?
Real rooms may not be perfectly diffuse, and absorption varies with frequency, placement, and installation. Air losses, furniture distribution, and irregular geometry can also shift RT60 from a simplified calculation.
7) What is a good RT60 for my room?
It depends on purpose and size. Speech spaces often benefit from shorter RT60, while music rooms can tolerate longer values. Use the target bands in the guide above as a practical starting point.
- Sabine estimates are best for moderately absorptive, well-mixed spaces.
- Highly absorptive or irregular rooms can deviate from this model.
- Use coefficients appropriate to your frequency range and materials.