Reverberation Time RT60 Calculator

RT60 Input Form

Enter room dimensions, choose the room type, then set octave-band absorption coefficients for each major surface and extra absorption source.

Room Length (m)

Room Width (m)

Room Height (m)

Room Use Target

Air Temperature (°C)

Relative Humidity (%)

Absorption Correction Factor

Additional Absorption Label

Surface Absorption Coefficients by Octave Band

Surface	125 Hz	250 Hz	500 Hz	1000 Hz	2000 Hz	4000 Hz
Floor
Ceiling
Front Wall
Back Wall
Left Wall
Right Wall
Seating, occupants, curtains, diffusers (sabins)

Use coefficients between 0 and 0.99. Additional absorption is entered directly in sabins for occupants, soft seating, curtains, or hanging treatment.

Example Data Table

This sample room uses carpet, an absorptive ceiling, painted walls, and moderate furnishing absorption.

Parameter	Example Value	Notes
Room dimensions	12 m × 8 m × 3.2 m	Medium classroom or training room.
Floor coefficient at 500 Hz	0.03	Reflects a hard vinyl or smooth surface.
Ceiling coefficient at 1000 Hz	0.85	Represents an absorptive acoustic tile ceiling.
Wall coefficient at 1000 Hz	0.08	Painted masonry or plaster is mildly absorptive.
Additional absorption at 1000 Hz	13 sabins	Accounts for seating, occupants, and curtains.
Target room use	Classroom / Speech Room	Seeks stronger speech clarity and controlled decay.

Formula Used

Room volume: V = L × W × H

Total surface area: S = 2LW + 2LH + 2WH

Equivalent absorption area: A = Σ(S_i × α_i) + A_extra

Sabine RT60: T = 0.161V / (A + 4mV)

Eyring RT60: T = 0.161V / (-S ln(1 - ᾱ) + A_extra + 4mV)

Average absorption coefficient: ᾱ = Σ(S_i × α_i) / S

Sabine performs well in lightly absorptive spaces. Eyring is often better when average absorption is higher because it accounts for exponential energy decay more realistically.

How to Use This Calculator

Enter room length, width, and height in meters.
Select the room use that best matches the design goal.
Review or edit octave-band absorption coefficients for floor, ceiling, and walls.
Enter extra absorption in sabins for furnishings, occupants, drapes, or added acoustic treatment.
Click Calculate RT60 to display results above the form.
Compare mid-band Eyring RT60 with the recommended target range.
Use the CSV or PDF buttons to export the current results.
Adjust absorption values until the room lands near the intended decay target.

FAQs

1. What does RT60 mean?

RT60 is the time required for sound energy to decay by 60 dB after the source stops. It describes how live or controlled a room sounds.

2. Why are six frequency bands used?

Absorption changes with frequency. A room may be controlled at 1000 Hz but still ring at 125 Hz. Band-by-band input reveals that imbalance.

3. Should I trust Sabine or Eyring more?

Sabine is common and simple. Eyring is usually more reliable when surfaces are fairly absorptive or when average absorption is not very low.

4. What are additional absorption sabins?

They represent absorption not directly tied to the six major room surfaces. Examples include people, upholstered seating, curtains, clouds, and movable treatment.

5. Why is the mid-band average highlighted?

Many acoustic targets are judged around 500 Hz and 1000 Hz because these bands strongly affect speech clarity and perceived room liveliness.

6. Can this replace on-site measurement?

No. It is a design and estimation tool. Final validation should use measured impulse responses or decay testing in the finished space.

7. What correction factor should I use?

Use 1.00 for normal estimates. Increase or decrease slightly when you want to reflect uncertainty in manufacturer data, surface coverage, or occupancy assumptions.

8. What if my result is too high?

Increase absorption, especially on ceilings and rear walls. For low frequencies, add thicker treatment or tuned control instead of relying only on thin panels.