Reverb Time Calculator

Two Equations, Two Levels of Precision

Room reverberation time can be estimated with more than one formula, and the choice matters more than it might seem. The Sabine equation, developed in the 1890s, is simple and accurate for moderately absorptive rooms, but it breaks down mathematically as absorption approaches 100% — a room with no reflective surfaces at all should have zero reverb, yet Sabine never quite reaches zero. The Eyring equation corrects for this and stays accurate in highly absorptive spaces like vocal booths and anechoic-adjacent rooms.

The Formulas

V is room volume in m³, A is total absorption in sabins, S is total surface area in m², and a is the average absorption coefficient (0 to 1, exclusive). Both formulas return RT60 — the time for reverberant sound to decay by 60 decibels.

When the Two Formulas Diverge

At low-to-moderate absorption coefficients the two equations produce nearly identical results, since ln(1−a) ≈ −a when a is small. The gap widens as absorption climbs: Sabine assumes the decay rate scales linearly with absorption, which becomes physically inaccurate for coefficients above roughly 0.3–0.4, where Eyring's logarithmic term captures the diminishing-returns effect of adding more absorptive material to an already-absorptive room.

Where This Gets Used

• Vocal booth and studio design — small, heavily treated spaces have high absorption coefficients, where Eyring gives a more trustworthy RT60 estimate.
• Concert hall and auditorium planning — large volumes with moderate absorption are well within Sabine's accurate range, and it remains the standard reference formula in that context.
• Comparing treatment options — running the same room through both formulas shows how sensitive the estimate is to the absorption assumption used.

How to Use This Calculator

1. Choose Sabine or Eyring mode.
2. Enter the room volume in cubic meters.
3. For Sabine mode, enter total absorption in sabins. For Eyring mode, enter surface area in square meters and the average absorption coefficient.
4. Select Calculate to see the estimated RT60 in seconds.

Related Calculations

Compute volume, surface area, and total absorption directly from room dimensions with the Room Acoustics Calculator, or check speaker impedance with the Speaker Impedance Calculator.