RT60 Reverb Time Calculator

How the RT60 reverb time calculator works

Use this RT60 reverb time calculator to estimate room reverberation time from room size, surface materials and absorption values. This page is about acoustic decay in rooms, not a music production reverb delay or effects calculator.

Reverberation time (RT60 or T60) describes how long it takes for sound to decay by 60 dB after the source stops. This calculator uses the Sabine formula — T = 0.161 × V / A — where V is room volume in cubic metres and A is total absorption in sabins. You enter room dimensions, select base surface materials, and optionally specify acoustic treatment coverage. The calculator then computes T60 per octave band and plots the decay curve so you can see whether your room is balanced or treating certain frequencies differently.

Estimated RT60, measured RT60 and Eyring RT60

Estimated RT60 predicts decay time from room volume and absorption coefficients before treatment is installed. Measured RT60 is taken from impulse response or decay measurements in the actual room and should guide final tuning. Eyring RT60 is a better estimate for heavily treated rooms, while Sabine-style estimation is most useful for lightly treated or moderately live rooms.

Related RT60 calculators

• RT60 Measurement Calculator for measured decay planning.
• Eyring RT60 Calculator for heavily treated rooms.
• Acoustic Panel Calculator for treatment coverage estimates.
• Schroeder Frequency Calculator for the modal-to-diffuse transition.

Sabine vs Eyring: which formula to use?

Sabine's formula is accurate for lightly treated rooms where the average absorption coefficient is below 0.3. Once a room is heavily treated — recording booths, control rooms, anechoic chambers — the Eyring formula is more reliable because it accounts for the increasing probability that sound will be absorbed on the first reflection rather than bouncing many times first. For most home studios and project rooms, Sabine gives results close enough to be useful for planning purposes.

Target RT60 values by room type

Different listening environments call for different reverberation times. A small home studio mixing room typically targets 0.25–0.40 s average, with the low end (125 Hz) ideally staying below 0.5 s. A home cinema aims for 0.3–0.4 s. A rehearsal room or practice space can tolerate 0.6–0.8 s. Large concert halls are designed around 1.8–2.2 s in the mid-frequency range. The goal is not simply "as dry as possible" — too short a decay makes speech difficult to understand and music fatiguing to listen to.

How material absorption works

Every surface in a room absorbs some fraction of incoming sound energy and reflects the rest. The absorption coefficient α runs from 0 (perfect mirror) to 1 (perfect absorber). Concrete and glass have α values around 0.02–0.05 across most frequencies, while 50 mm mineral wool can exceed 0.90 above 500 Hz. Low frequencies are the hardest to absorb — thin panels have little effect below 200 Hz, which is why RT60 is almost always longer at bass frequencies than at mid or high frequencies. Adding a thick porous absorber or a tuned resonator panel is the primary way to address excess bass reverberation.

Key terms

• Sabine T₆₀ — T = 0.161 × V/A; A is total absorption in sabins. One sabin equals one square metre of perfectly absorbing surface.
• Absorption coefficient (α) — fraction of incident sound energy absorbed per surface encounter, measured at each octave band from 125 Hz to 4 kHz.
• Octave bands — standard frequency groupings (125, 250, 500, 1k, 2k, 4k Hz) used in acoustic reporting and measurement standards.
• Sabin — unit of acoustic absorption equal to 1 m² of a perfectly absorbing surface; total absorption A = sum of (α × area) for all surfaces.
• Air absorption — at high frequencies above 2 kHz, air itself absorbs sound energy; relevant for large rooms where path lengths are long.

Frequently asked questions

• What T60 is good for a recording studio? A small-to-medium control room typically targets 0.3–0.5 s average, with T60 as consistent as possible across the frequency range. Avoid having the bass decay much longer than the mid-range, which causes a boomy character that makes mix decisions unreliable.
• What is the difference between Sabine and Eyring formulas? Sabine's formula assumes sound bounces many times before being absorbed, which is accurate for rooms with low average absorption (α below 0.3). Eyring's formula corrects for heavily damped rooms where much of the energy is absorbed early. For typical home studio planning, Sabine is accurate enough.
• How do I reduce reverberation time in my room? Add surface absorption using porous materials such as mineral wool panels, thick fabric, carpet, and soft furnishings. The more total absorption area you add, the shorter the RT60. Bass frequencies require thick absorbers (100 mm or more) or tuned resonant traps. Avoid placing all treatment on one surface — spread it across multiple walls and the ceiling for even decay.
• Why does my room sound brighter at high frequencies? Hard surfaces like concrete, plaster, and glass reflect high-frequency energy efficiently. If your room lacks soft furnishings or broadband panels, the result is a harsh, splashy character. Fabric panels absorb highs easily; low-frequency treatment requires more material depth.
• How much acoustic treatment do I need? A rough starting point is to treat 20–30% of the total surface area with 100 mm mineral wool panels. Run this calculator with your room dimensions and current materials, then gradually add treatment coverage until the displayed T60 hits your target. Pay particular attention to getting the 125 Hz and 250 Hz bands to match the mid-frequency values as closely as possible.
• Why is bass RT60 always longer than mid-range? Low-frequency wavelengths are long — the 125 Hz octave band has a wavelength of about 2.7 m. Most room surfaces and thin absorbers have very little effect at these wavelengths. Effective low-frequency absorption requires thick porous absorbers (150 mm+), corner placement, or resonant panels tuned to the problem frequency. This is why bass trapping is often the first priority in studio acoustic treatment.