Acoustic panel calculator: how many panels, and where they go
This acoustic panel calculator answers the two questions everyone asks before treating a room: how many acoustic panels do I need, and where should they go? Enter the room size and surfaces, choose a target reverberation time and a panel type, size and thickness, and it works out the smallest number of panels that brings the mid-frequency RT60 down to the target. It then finds the first reflection points on the side walls and ceiling for your speakers and seat, and draws them on a plan.
It is for home studios, podcast rooms, home cinemas, offices and classrooms, in metres or feet. The maths runs in your browser using the same materials table as the RT60 calculator.
How to use the Acoustic Panel Calculator
- Enter the room length, width and height, and pick the floor, ceiling and wall materials.
- Add rugs, curtains or a sofa as items, with their area.
- Choose a target RT60 and a panel type and thickness, then the panel size and whether it goes on the walls or the ceiling.
- Enter where the speakers and your seat are to get the reflection points.
- Read the panel count, the RT60 before and after by octave band, and the plan. Press Copy result to keep it.
Acoustic Panel Calculator features
Sabine and Eyring inverted
The panel count from both formulas, so you see the range.
Panels by thickness
16 generic panels (glass wool, rock wool, melamine and polyurethane foam, 12–100 mm) or your own test data.
Band-by-band check
Shows how many panels each band would need, which reveals when bass traps are needed rather than more thin panels.
Mirror-image reflection points
Side walls, ceiling, floor, front and rear wall for each speaker, with delay and level.
Plan sketch
A top view with the speakers, the seat, the reflection paths and a panel drawn at each side-wall point.
How the panel count is worked out
Sabine’s formula is RT60 = 0.161 × V ÷ A, so the absorption needed for a target time T is A = 0.161 × V ÷ T (0.049 in feet). Each panel mounted flat on a surface adds its area times the difference between its coefficient and that of the surface it covers. The calculator adds panels one at a time and stops at the smallest number whose 500 Hz–2 kHz average meets the target. Eyring’s formula, RT60 = 0.161 × V ÷ (−S × ln(1 − ᾱ)), inverts to a required mean coefficient ᾱ = 1 − e^(−0.161 V ÷ (S T)); it gives a smaller count in well-damped rooms.
Worked example: a bare 10 × 10 × 3 m concrete room (320 m² of surface) has 6.4 m² sabins at 1 kHz and a mid-frequency RT60 of about 8.4 s. Reaching 0.8 s needs 0.161 × 300 ÷ 0.8 = 60.4 m² sabins. A 1.2 × 0.6 m panel that absorbs everything at mid frequencies adds 0.72 × (1 − 0.02) ≈ 0.71 m² sabins, so it takes 78 panels (Eyring: 70), covering 47% of the walls. A furnished room needs far fewer.
Panel thickness and NRC
Thickness decides the lowest frequency a panel absorbs well: 25 mm works from about 1 kHz up, 50 mm from 500 Hz, and 100 mm (or a panel spaced off the wall) reaches into the 125–250 Hz range. NRC is the average of the 250 Hz–2 kHz coefficients rounded to 0.05, so it hides the bass. Sources: the akustik.ua absorption-coefficient table (glass wool, rock wool, melamine and flexible foam) and the sengpielaudio table (polyurethane and profiled foam), checked 24 October 2026; lab values above 1 are capped at 1.
| Generic panel | 125 Hz | 500 Hz | 2 kHz | NRC |
|---|---|---|---|---|
| Glass wool 25 mm, 24 kg/m³ | 0.11 | 0.56 | 0.89 | 0.65 |
| Glass wool 50 mm, 48 kg/m³ | 0.30 | 1.00 | 1.00 | 0.95 |
| Glass wool 100 mm, 48 kg/m³ | 0.65 | 1.00 | 1.00 | 1.00 |
| Polyurethane foam 25 mm | 0.13 | 0.68 | 0.92 | 0.70 |
| Profiled foam 50 mm | 0.06 | 0.56 | 0.90 | 0.65 |
Finding first reflection points
Sound from each speaker bounces off the side walls, ceiling and floor and reaches you a few milliseconds after the direct sound, blurring the stereo image. The mirror trick finds the spot: reflect your seat in the wall, draw a line from the speaker to that image, and the reflection point is where the line meets the wall. This is what the “sit and slide a mirror along the wall” method does by eye. Put a panel at each side-wall point and a cloud over the two ceiling points; a rug covers the floor ones. For placing the speakers themselves, use the speaker placement calculator; for bass resonances, the room mode calculator.
Acoustic Panel Calculator FAQ
How many acoustic panels do I need?
It depends on the room volume, what is already in it and your target. This acoustic panel calculator adds panels until the mid-frequency RT60 meets the target; the furnished 60 m³ example room that opens with the page needs 20 panels of 1.2 × 0.6 m, 50 mm glass wool, to reach 0.4 s (16 by Eyring).
What thickness of acoustic panel should I buy?
For speech and vocals 50 mm is the usual minimum. Use 100 mm, or 50 mm with an air gap behind, when you also need to tame 125–250 Hz. Thin 25 mm foam mainly absorbs treble.
Where do I put acoustic panels first?
At the first reflection points on the side walls, then over the listening position on the ceiling, then on the rear wall. Add bass traps in the corners if the low bands stay long.
What is a good NRC for acoustic panels?
NRC 0.8 or more is good for a broadband absorber. Two panels with the same NRC can differ a lot at 125 Hz, so check the full table.
Is it Sabine or Eyring I should trust?
Sabine is the usual design formula and slightly conservative; Eyring is more accurate in rooms with a lot of absorption. The truth for a real room usually lies between the two counts.
Can I cover a whole wall with panels?
You can, but the room may end up dull, and covering every wall leaves flutter between untreated ones. Spread panels over several surfaces and aim for the target, not for zero reverb.