About the Reverb Time (RT60) Calculator
Reverberation time, RT60, is how long a sound takes to fade by 60 dB after the source stops. It is the single most useful number for describing how “live” or “dead” a room sounds. This calculator estimates RT60 in six octave bands from 125 Hz to 4 kHz using the classic Sabine formula, with the Eyring formula alongside for rooms that are already well damped.
Enter the room dimensions, choose a material for the floor, walls and ceiling, and add any area of acoustic panels. The result shows how much absorption the room has, which frequencies ring the longest, and how much treatment changes the decay. It suits home studios, rehearsal rooms, podcast booths, classrooms and home theatres.
Coefficients are typical published values for common finishes; real products vary, and furniture, people and doors add absorption the model does not count. Sabine also assumes sound is spread evenly, which is least accurate in very small or very dead rooms.
With the default inputs, the rt60 (mid, 500 hz–1 khz) is 1.07 s. Change any value above to recalculate instantly.
How to use the reverb time (rt60) calculator
- 1Choose metres or feet and enter the room’s length, width and height.
- 2Pick the closest material for the floor, walls and ceiling.
- 3Add the total area of any acoustic panels mounted on the walls.
- 4Read the mid-frequency RT60 and compare it with the target for your room.
- 5Check the octave-band chart to see whether bass or treble rings longer.
Formula and method
Wallace Sabine found that reverberation time is proportional to room volume and inversely proportional to the total absorption. Absorption A is the sum, over every surface, of its area times its absorption coefficient α (0 = perfectly reflective, 1 = perfectly absorptive), measured in sabins. The constant 0.161 s/m (0.049 s/ft) comes from the speed of sound and the definition of a 60 dB decay.
This tool applies the formula separately in each octave band using typical coefficients for each finish. The headline value averages the 500 Hz and 1 kHz bands. The Eyring variant uses the average coefficient ᾱ = A ÷ S and gives shorter, more realistic times when ᾱ rises above roughly 0.2; air absorption is ignored, which matters only in large halls at high frequencies.
- RT60
- Time for sound to decay by 60 dB, seconds
- V
- Room volume (m³ or ft³)
- Sᵢ, αᵢ
- Area and absorption coefficient of each surface
- A
- Total absorption in sabins
- S, ᾱ
- Total surface area and average absorption coefficient
Worked examples
Untreated bedroom studio, 5 × 4 × 2.5 m
The 50 m³ room has 20 m² of carpet, 20 m² of drywall ceiling and 45 m² of drywall walls. At 500 Hz that is 20 × 0.14 + 20 × 0.05 + 45 × 0.05 = 6.05 sabins, so RT60 = 0.161 × 50 ÷ 6.05 ≈ 1.33 s. At 1 kHz the carpet absorbs more (10.0 sabins, 0.81 s), giving a mid average of about 1.07 s — far too live for mixing.
Same room with 12 m² of 2-inch panels
Replacing 12 m² of drywall with panels (α ≈ 1.0 at 500 Hz and 1 kHz) adds 12 × (1.0 − 0.05) = 11.4 sabins at 500 Hz, raising absorption to 17.45 sabins and cutting RT60 to 0.161 × 50 ÷ 17.45 ≈ 0.46 s. The mid average drops to about 0.42 s.
Classroom in feet with a tile ceiling
The room is 7,500 ft³. At 500 Hz the vinyl floor adds 750 × 0.03 = 22.5 sabins, the block walls 1,100 × 0.06 = 66 and the acoustic tile ceiling 750 × 0.72 = 540, for 628.5 sabins. RT60 = 0.049 × 7,500 ÷ 628.5 ≈ 0.58 s, just inside the 0.6 s limit ANSI/ASA S12.60 sets for classrooms of this size.
Frequently asked questions
What is a good RT60 for a room?+
Rough guides: vocal booths 0.1–0.3 s, control rooms and home studios 0.2–0.4 s, living rooms and home theatres 0.3–0.5 s, classrooms about 0.6 s or less, and concert halls 1.5–2.2 s.
What is the Sabine formula?+
RT60 = 0.161 × V ÷ A in metric units, where V is volume in cubic metres and A is total absorption in metric sabins (square metres of perfect absorber). In feet the constant is 0.049.
When should I use Eyring instead of Sabine?+
Eyring is more accurate when the room is fairly absorptive (average coefficient above about 0.2). Sabine overestimates reverb time in dead rooms, but both agree closely in live rooms.
Why does my room still boom after adding foam panels?+
Thin foam and 2-inch panels absorb mids and highs well but very little below about 250 Hz. Low-frequency decay needs thick porous traps (100 mm or more), ideally in corners, or tuned membrane absorbers.
What is a sabin?+
A sabin is a unit of sound absorption equal to one square metre (metric) or one square foot (imperial) of a perfectly absorbing surface. A 2 m² panel with α = 0.8 provides 1.6 metric sabins.