🎚️ Reverb Time Calculator
Calculate a room's RT60 reverberation decay time from its dimensions and surface absorption using the Sabine formula.
Volume: 90 m³ • Surface area: 126 m² • Absorption: 18.9 sabins
What Is Reverb Time (RT60)?
Reverberation time, or RT60, is how long it takes a sound to decay by 60 decibels — to roughly one-millionth of its original energy — after the source stops. It is the single most important number describing how a room sounds. A short reverb time makes speech crisp and music tight; a long one produces the washy, echoing decay you hear in a church or empty gym. The “decay” people search for is exactly this RT60 value.
The Sabine Formula
This calculator uses the Sabine equation, the classic model of room acoustics: RT60 = 0.161 × V ÷ Ain metric units, where V is the room volume in cubic metres and A is the total absorption in sabins. In imperial units the constant is 0.049 with volume in cubic feet. Absorption A is the room’s total surface area multiplied by its average absorption coefficient — a number from 0 (perfectly reflective) to 1 (perfectly absorbent). The more soft, absorbent material a room contains, the larger A becomes and the shorter the reverb time.
We estimate total surface area from your length, width, and height as 2 × (LW + LH + WH), then multiply by the average absorption coefficient for the room finish you select. The presets are mid-frequency approximations; choose “Custom” to enter a measured coefficient for a more precise result.
What Reverb Time Should a Room Have?
There is no single ideal — it depends on use. Recording studios and home theaters aim for roughly 0.2–0.4 seconds so detail is not smeared. Classrooms and offices target about 0.4–0.7 seconds for clear speech. Living rooms typically land near 0.4–0.6 seconds. Concert halls are deliberately live at 1.8–2.2 seconds to give orchestral music warmth and bloom. If your result is too long, add absorption: carpet, heavy curtains, upholstered furniture, bookshelves, and acoustic panels all raise A and shorten the decay.
Limitations
The Sabine formula is most accurate in fairly “live” rooms with evenly distributed absorption and average coefficients below about 0.3; very dead or oddly shaped rooms are better modeled by the Eyring equation. Real reverb time also varies with frequency — bass usually decays more slowly than treble — so treat this single figure as a broadband estimate rather than a measured value.