Reverb Time Calculator (RT60)

Room Inputs

Unit system *

Constants adapt automatically: 0.161 (metric) or 0.049 (imperial).

Calculation method *

Use Eyring when average absorption is high.

Room model *

Custom mode supports non‑rectangular spaces.

Length * (m)

Width * (m)

Height * (m)

Surface Absorption

Absorption mode *

Frequency band (for presets)

Presets are typical values, adjust as needed.

Air attenuation coefficient (1/m)

Optional: adds 4·m·V to absorption.

Floor material

Floor α (0–1)

Ceiling material

Ceiling α (0–1)

Wall material

Walls α (0–1)

Rectangular rooms compute areas automatically: floor, ceiling, and all walls.

Extras and Occupancy

People count

Absorption per person (sabins)

Typical at mid frequencies; adjust for your case.

Extra absorbers

Add rugs, curtains, panels, or furniture using area and α.

Item	Area (m²)	α (0–1)

Results appear above this form after calculation, right below the header.

Example Data Table

Sample scenarios using rectangular rooms and typical mid‑band coefficients.

Scenario	L×W×H	Floor α	Ceiling α	Walls α	Extras (sabins)	Method	RT60 (s)
Small home studio	4×3×2.5	0.20	0.60	0.05	6	Sabine	0.35
Classroom	8×6×3	0.10	0.70	0.06	12	Eyring	0.55
Lecture hall	18×12×6	0.08	0.75	0.04	40	Sabine	1.10

These are illustrative only; real coefficients depend on construction and frequency.

Formulas Used

Total absorption: A = Σ(Sᵢ·αᵢ) + A_extras + A_people + 4·m·V
Sabine (RT60): RT60 = k·V / A, where k = 0.161 (metric) or 0.049 (imperial)
Eyring (RT60): RT60 = k·V / ( -S·ln(1 - ᾱ) ), where ᾱ = A/S

Sabine is widely used for low to moderate absorption. Eyring can behave better when the average absorption is high, because it accounts for multiple reflections more explicitly.

How to Use This Calculator

Select unit system and choose Sabine or Eyring.
Pick Rectangular or Custom room mode for your geometry.
Enter dimensions (or total V and S for custom rooms).
Provide absorption using floor/ceiling/walls, average ᾱ, or total A.
Add extras like curtains or panels, and optional audience absorption.
Click Calculate RT60 to see results above the form.
Use Download CSV or Download PDF to save outputs.

Reverberation time describes how long sound lingers in a room after the source stops. This page estimates RT60 using common acoustics models and your room, surface, and material inputs.

For planning, combine this estimate with listening tests, because HVAC noise, openings, and furnishings can often shift real decay times indoors noticeably.

1) What RT60 Represents

RT60 is the time, in seconds, for sound energy to drop by 60 dB. Lower values feel “dry” and improve speech clarity; higher values feel “live” and add sustain. Many small rooms land between 0.3 and 0.9 s, depending on purpose.

2) Practical Target Ranges

Use targets as a starting point: voice booths 0.2–0.5 s, classrooms 0.5–0.8 s, conference rooms 0.4–0.7 s, home theaters 0.3–0.6 s, small rehearsal rooms 0.6–1.2 s, and concert halls about 1.6–2.2 s. Very large churches can exceed 3.0 s.

3) Sabine vs Eyring

Sabine works well when average absorption is modest and is widely used for quick planning. Eyring adds a logarithmic correction that better handles higher absorption, so results can differ when ᾱ rises. Comparing both helps you judge sensitivity and avoid overconfidence.

4) Volume and Surface Area Effects

RT60 increases with room volume V and decreases with total absorption A. If materials stay the same, doubling V roughly doubles RT60. Rectangular mode computes surface area from length, width, and height, while custom mode lets you enter total V and S directly.

5) Absorption Coefficients and Total A

Each surface contributes A = S × α. Typical mid-band α values: painted concrete 0.01–0.03, plaster 0.03–0.06, plywood 0.05–0.10, carpet on pad 0.35–0.60, acoustic ceiling tile 0.50–0.80, and heavy curtains 0.40–0.70. Enter per-surface details when you know them.

6) Frequency Bands Explain “Boomy” Rooms

Rooms often ring longer at low frequencies because many finishes absorb less bass. Adding panels may reduce 500–4000 Hz strongly but leave 125–250 Hz high, which listeners perceive as “boomy.” Octave-band RT60 output is useful for spotting that imbalance.

7) Interpreting and Improving Results

If RT60 is too high, increase absorption (carpet, panels, curtains), add occupied seating, and reduce large parallel reflective areas. If it is too low for music, remove some absorption, add reflective elements, or increase volume. Confirm final designs with in-room measurements whenever possible.

FAQs

1) What inputs do I need for a rectangular room?

Enter length, width, and height, then choose how you want to describe absorption: per-surface materials, an average absorption coefficient, or total absorption area A.

2) When should I choose the Eyring method?

Use Eyring when the room has higher overall absorption, such as thick carpet, many panels, or heavy drapes, because it better accounts for multiple reflections as absorption increases.

3) Why are my low-frequency RT60 values higher?

Most finishes absorb less at 125–250 Hz than at mid and high bands, so bass energy decays more slowly. Adding bass traps or thicker porous absorbers can reduce the low-band RT60.

4) How does audience seating affect reverberation?

People and upholstered seats add significant mid/high absorption, often lowering RT60 noticeably in occupied conditions. Model seating as extra absorption area, and compare “empty” versus “occupied” results for realistic planning.

5) Is this result accurate enough for construction decisions?

It is a strong estimate for early design and comparisons, but real rooms vary due to leakage, diffusion, and mounting details. Verify critical spaces with measurement or professional modeling before final purchase and installation.

6) What is a good RT60 for speech clarity?

For most speech-focused spaces, 0.4–0.8 seconds is a common target range. Smaller rooms often sit near the lower end, while larger classrooms may need closer to 0.7–0.8 seconds.