RT60 Calculator

Free tool to calculate the reverberation time of a room from its size and materials. No sign-up

Enter the length, width and height of the room, in metres or feet, and the air temperature.
Choose the material of the floor, the ceiling and the two pairs of walls, and add the absorption of furniture and people if you know it.
Pick a target for the kind of room you have, such as a control room or a theatre.
Read the RT60 per octave band with Sabine and Eyring, the mid-frequency value and how much absorption you would need to add or remove.
Check the chart against the target, then download the results as CSV or copy them as text.

Extra absorption is what furniture, people and objects add: one person is about 0.4 to 0.5 m² sabins at mid frequencies. With a target chosen, values outside its range are highlighted.

Nothing is saved or uploaded: everything stays in your browser. Download or copy your results before closing the page. Sabine and Eyring assume a diffuse sound field, so small rooms and low frequencies can differ a lot from the result. The absorption coefficients are typical table values and vary between products, and the target ranges are rules of thumb: use the result as an estimate and measure the room when you need accuracy.

How do you calculate the RT60 reverberation time of a room?

RT60 is the time sound takes to fade by 60 dB after the source stops. The Sabine formula gives it as RT60 = 0.161 × V ÷ A, where V is the room volume in m³ and A is the total absorption in m² sabins, found by adding up each surface area multiplied by its absorption coefficient. A room of 5.5 × 4.2 × 2.7 m has a volume of 62.4 m³, and with about 11 m² sabins of absorption at 500 Hz its RT60 is about 0.9 s. For very absorbent rooms the Eyring formula is more accurate. This free calculator applies both to each octave band from 125 Hz to 4 kHz and compares the result with a target for your kind of room.

What is RT60?

Clap your hands in an empty room and you hear the sound linger and fade: that tail is the reverberation. RT60 is how long it takes to become a million times weaker, which is 60 decibels. Hard, bare surfaces like concrete, glass and tiles reflect sound and make the tail long. Soft or porous materials like carpet, curtains and mineral wool panels absorb it and make the tail short. Different rooms need different times: a control room or a vocal booth should be short and dry, a classroom short enough for speech to stay clear, a concert hall much longer. Bass is harder to absorb than treble, so the result is given for each octave band.

Made by Luca Martone, sound designer and live sound engineer based in Turin.
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