Reverberation Time Calculator
From a room's volume, surface area, and average absorption, get the RT60 and the total absorption — the numbers that tell you how live or how dead a room sounds.
Three inputs, the RT60
Enter the room volume, the total surface area, and the average absorption coefficient and the calculator returns the Sabine reverberation time (0.161·V/A) and the total absorption (S·α).
Sabine is an estimate
The Sabine formula works best for fairly live rooms with evenly spread absorption; very dead rooms or patchy treatment need more advanced models.
What is a reverberation time calculator?
Room size and absorption in, RT60 out
A reverberation time calculator turns three measurements — the room's volume, its total interior surface area, and how absorbent those surfaces are on average — into the RT60, the time it takes for a sound to fade by 60 decibels (to about a thousandth of its energy) after the source stops. RT60 is the single most-used number in room acoustics: it tells you whether a space sounds boomy and echoey or tight and dead. That makes it the starting point for designing classrooms, home studios, offices, churches, and home theatres, or for deciding how much acoustic treatment a room needs.
Enter the volume, surface area, and average absorption to get the RT60 and total absorption instantly.
Two short steps, both from the Sabine equation. First the total absorption, then the reverberation time, with the metric Sabine constant 0.161.
RT60 = 0.161 × V / (S × α)The total absorption A is the surface area S times the average absorption coefficient α — measured in metric sabins (m²). The reverberation time is then 0.161 × V / A: it grows with the room volume (bigger rooms ring longer) and shrinks as you add absorption. The constant 0.161 carries the metric units (s·m⁻¹); the imperial version of the formula uses 0.049.
Suppose a room has a volume of 200 m³, a total surface area of 240 m², and an average absorption coefficient of 0.2.
Total absorption
A = 240 × 0.2 = 48 metric sabins (m²) — the room's effective absorbing area.
Reverberation time
RT60 = 0.161 × 200 / 48 = 32.2 / 48 = 0.670833 s — a fairly lively but controlled room.
The RT60 tells you how a room will sound and what it suits. As a rule of thumb, a reverberation time of roughly 0.3–0.6 s is right for speech — classrooms, meeting rooms, podcast studios, and home theatres — because short reverberation keeps consonants crisp and intelligible. Longer times, around 1.5–2.5 s, flatter music: concert halls and churches use the lingering decay to blend and enrich sound, which is why singing in a cathedral feels grand. The example above (0.67 s) is a touch live for critical speech but fine for a general-purpose room. The two levers are clear from the formula: the RT60 rises with volume, so big rooms naturally ring longer, and it falls as you add absorption — doubling the average coefficient α (with carpet, curtains, panels, or people, who are excellent absorbers) roughly halves the reverberation time. If your space sounds boomy, the cure is more absorption, not a smaller room.
The Sabine formula is a fast, trusted estimate, but a couple of practical points are worth keeping in mind.
An estimate, frequency-dependent, metric units
The Sabine equation assumes a diffuse sound field with absorption spread fairly evenly around the room; it overestimates the reverberation time for very dead rooms (where the Eyring formula is better) or where all the absorption sits on one surface. Absorption coefficients also vary with frequency — a material that soaks up treble may barely touch bass — so a single average α gives one broadband figure, not the full picture. The inputs here are metric (V in m³, S in m², α dimensionless) and the 0.161 constant matches them, so the RT60 comes back in seconds.