Reverberation Time Calculator

Reverberation time describes how long sound persists in an enclosed space after its source stops. RT60 is conventionally defined as the time required for the sound-pressure level to decay by sixty decibels. A long RT60 creates a lively or echoing impression, while a short RT60 sounds controlled and dry. The appropriate value depends on room volume and purpose: speech rooms usually need clarity, whereas concert spaces may benefit from a longer decay that supports music. This calculator uses the metric form of Sabine's equation. RT60 equals 0.161 times room volume divided by equivalent absorption area. For a rectangular room, volume is length times width times height and total boundary area is twice the sum of the floor, two wall pairs, and ceiling products. The simplified model multiplies that area by one average absorption coefficient. A coefficient of zero represents ideal reflection, while one represents ideal absorption. Real finishes fall between those limits and vary with frequency. Equivalent absorption area is measured in metric sabins, with one sabin corresponding to one square meter of perfectly absorbing surface. A more detailed room calculation adds each surface area multiplied by that material's absorption coefficient. The average coefficient used here should represent that area-weighted combination, including carpet, ceiling tile, wall panels, glazing, doors, seats, and occupants. Furniture and air absorption can also matter, especially in large rooms or at high frequencies. Architects, studio designers, educators, and audio engineers use RT60 estimates to compare acoustic treatments and establish design targets. Adding absorptive material increases equivalent absorption and shortens decay. Increasing volume without adding absorption lengthens decay. Because coefficients depend on octave band, professional analysis calculates separate values across frequencies rather than relying on one broadband average. Occupancy is particularly important because an empty hall can behave differently from the same space with a full audience. Sabine's equation assumes a diffuse sound field with absorption distributed reasonably evenly and is most reliable when average absorption is not high. It does not model strong echoes, room modes, coupled spaces, irregular geometry, scattering, or treatment placement. Eyring's formula may better represent highly absorptive rooms. Measurements can also differ because RT60 is often extrapolated from shorter measured decay ranges. Use this calculator for early planning and comparisons, then verify important designs with frequency-specific material data, acoustic simulation, or standardized measurements in the completed room.