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Reverberation Time Calculator (Sabine Equation)

Estimate a room's reverberation time (RT60) from its volume, surface area, and average sound absorption coefficient, using Sabine's equation.

Reverberation time (RT60)
1.006 s
Category
Typical living space or small venue
Total absorption
24 metric sabins

Where this falls

1 falls in the "Typical space" range.

How it works

Sabine's equation is the standard room-acoustics estimate for reverberation time: RT60 = 0.161 × V ÷ A, where V is the room's volume in cubic meters and A is its total sound absorption in metric sabins (surface area times the fraction of sound energy it absorbs rather than reflects). RT60 is the time for a sound to decay by 60 decibels — the conventional definition of 'how long the echo lasts.'

The 0.161 constant isn't an empirical fudge factor — it falls out of the derivation as 24 × ln(10) ÷ c, where c is the speed of sound (~343 m/s), based on the mean distance sound travels between reflections and how many decibels of decay 60 dB actually requires. Imperial inputs are converted to cubic meters and square meters before this one formula runs, the same canonical-unit approach this site's Hydrostatic Pressure calculator uses for depth.

This uses a single average absorption coefficient across every surface rather than a material-by-material breakdown (carpet, drywall, glass, etc. each absorb differently) — the standard simplified form of Sabine's equation used for a quick estimate when you don't have a full surface-by-surface inventory.

FAQ

What absorption coefficient should I use if my room has a mix of surfaces?

A rough area-weighted average: mostly hard surfaces (drywall, tile, glass, bare floor) sit around 0.02-0.1, a furnished room with some soft furnishings lands around 0.15-0.3, and a heavily carpeted, curtained, upholstered room can reach 0.4-0.5 or higher. This calculator can't know your specific materials, so treat the result as an estimate that's most useful for comparing 'what if I added more soft furnishing' scenarios rather than a lab-grade measurement.

Is a shorter RT60 always better?

No — it depends on the room's purpose. A very short RT60 (well under 0.3s) sounds 'dead' and unnatural for music, while a long one (over 1.5-2s) muddies speech. Recording studios and classrooms aim short for clarity; concert halls deliberately aim longer to give music warmth and blend, which is why the category shown alongside your result names the kind of space each range suits rather than labeling any value as simply 'good' or 'bad.'

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