RT60 is the time in seconds for sound to decay by 60 dB after the source stops. It is the primary measure of room acoustics. A recording studio targets 0.3–0.5 sec. A concert hall targets 1.5–2.5 sec. A reverberant cathedral can exceed 5 seconds.

What is the Sabine equation?

The Sabine formula is RT60 = 0.049 × V / A (in feet), where V = room volume in cubic feet and A = total absorption in sabins. One sabin = one square foot of perfect absorber (absorption coefficient = 1.0).

When should I use the Eyring formula instead?

The Eyring formula is more accurate when average absorption exceeds 0.3. Sabine overestimates RT60 in very absorptive rooms. Eyring: RT60 = 0.049V / (−S × ln(1−α_avg)), where S = total surface area and α_avg = average absorption coefficient.

How do I calculate total absorption (sabins)?

For each surface: multiply its area (ft²) by its absorption coefficient (α). Sum all surfaces. Example: 500 ft² carpet at α=0.35 = 175 sabins. 800 ft² drywall at α=0.05 = 40 sabins. Total = 215 sabins.

Reverb Time Calculator (RT60)

Calculate room RT60 reverb time using the Sabine equation. Enter room volume and total absorption to get decay time in seconds. Includes Eyring formula for accurate results in absorbent rooms.

Room Volume (cubic feet) ?

ft³

Total Absorption (sabins) ?

sabins

RT60 (Sabine)

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Room Type Recommendation —

Assessment —

Extended More scenarios, charts & detailed breakdown ▾

Length (ft)

Width (ft)

Height (ft)

Floor Material

Wall Material

Ceiling Material

RT60 (Sabine)

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Room Volume —

Total Absorption —

Room Assessment —

Professional Full parameters & maximum detail ▾

Room Volume (ft³)

ft³

Total Absorption (sabins)

sabins

Average Absorption Coefficient (0–1) ?

Total Surface Area (ft²)

ft²

RT60 Calculations

RT60 — Sabine Formula —

RT60 — Eyring Formula —

Difference (Sabine vs Eyring) —

RT60 Targets by Use

Target: Recording Studio —

Target: Classroom —

Target: Concert Hall —

Treatment Goal

Absorption Needed for Studio —

How to Use This Calculator

Enter your Room Volume in cubic feet (Length × Width × Height).
Enter the Total Absorption in sabins (sum of area × alpha for all surfaces).
Read the RT60 reverb time and room assessment.
Use the From Room Dimensions tab to auto-calculate absorption from materials.
Use the Professional tier for both Sabine and Eyring formulas side by side.

Formula

Sabine: RT60 = 0.049 × V ÷ A (V in ft³, A in sabins)

Eyring: RT60 = 0.049 × V ÷ (−S × ln(1 − α_avg))

Eyring is more accurate when α_avg > 0.3.

Example

Room: 25×20×10 ft = 5,000 ft³. Estimated absorption = 500 sabins. RT60 = 0.049 × 5,000 ÷ 500 = 0.49 seconds — excellent for a recording studio.

Frequently Asked Questions

RT60 is the time in seconds for sound to decay by 60 dB after the source stops. It is the primary measure of room acoustics. A recording studio targets 0.3–0.5 sec. A concert hall targets 1.5–2.5 sec. A reverberant cathedral can exceed 5 seconds.
The Sabine formula is RT60 = 0.049 × V / A (in feet), where V = room volume in cubic feet and A = total absorption in sabins. One sabin = one square foot of perfect absorber (absorption coefficient = 1.0).
The Eyring formula is more accurate when average absorption exceeds 0.3. Sabine overestimates RT60 in very absorptive rooms. Eyring: RT60 = 0.049V / (−S × ln(1−α_avg)), where S = total surface area and α_avg = average absorption coefficient.
For each surface: multiply its area (ft²) by its absorption coefficient (α). Sum all surfaces. Example: 500 ft² carpet at α=0.35 = 175 sabins. 800 ft² drywall at α=0.05 = 40 sabins. Total = 215 sabins.

Related Calculators

Sources & References (5) ▾

Architectural Acoustics Illustrated — Acoustical Society of America
AES Handbook of Recording Engineering — Audio Engineering Society
Room Acoustics and RT60 — Sound on Sound
Acoustic Treatment for Studios — Acoustic Sciences Corporation
Acoustic Absorbers and Diffusers — Cox & D'Antonio (Routledge)