How Many Acoustic Panels Do You Need? A Simple Room Calculation
The most common question we get about acoustic panels is not which panel to buy. It is how many. Acoustic consultants answer it with reverberation time calculations, and for schools, auditoriums and offices with formal requirements that is the right path. But for most rooms a simple estimate gets you close enough to buy confidently. Here is the method we use when customers describe a room to us.
The quick rule
For a typical room with hard surfaces, plan absorptive panel area equal to 15 to 30 percent of the floor area, using an effective absorber such as wood wool cement board (fibrolite) at 25 mm, ideally with an air gap.
- 15 to 20 percent: noticeable improvement. Echo softens, speech gets easier. Right for living rooms, bedrooms, small offices.
- 20 to 30 percent: strong treatment. Right for meeting rooms, classrooms, restaurants, video call rooms and anywhere speech clarity is the goal.
- Above 30 percent: specialist territory: home cinemas, recording spaces, very tall or glassy rooms, or rooms that must meet a documented reverberation target.
Worked example 1: home office
A 3.5 x 4 m room is 14 m2 of floor. Twenty percent is roughly 2.8 m2. That is eight 600 x 600 panels, or a single band of 2400 x 600 panels behind the desk plus a small ceiling field above it. In a room this size, that turns a harsh video call echo into a calm, dry sound.
Worked example 2: meeting room
A 5 x 6 m meeting room is 30 m2. Twenty five percent gives 7.5 m2 of panel. The classic layout is a ceiling field of about 5 m2 over the table plus 2 to 3 m2 on one wall, ideally the wall facing the video conference screen so the camera microphone stops picking up reflections.
Worked example 3: restaurant dining room
A 120 m2 dining room at 25 to 30 percent needs 30 to 36 m2 of absorber. On a ceiling that is a nearly continuous treated zone above the seating areas. This is where wood wool pallet quantities make sense: one pallet of 25 mm Sonablock carries 30.96 m2, almost exactly the requirement.
Where to put the panels
Placement matters nearly as much as quantity:
- Ceiling first. It is the largest uninterrupted surface and treats the whole room evenly.
- First reflection points. Walls halfway between the sound source and the listener. In offices, that means panel bands at seated head height, roughly 1.0 to 2.0 m from the floor.
- Opposing hard walls. If two bare parallel walls face each other, treat at least one to stop flutter echo.
- Do not aim for 100 percent coverage. Rooms need some liveliness. Beyond the targets above, extra panels add cost and visual weight for little audible gain.
Height and hard finishes shift the target
Ceilings above 3 m, glass walls, and stone or concrete floors all add reverberation. For each of those factors present, move toward the top of the percentage range. A glassy 4 m tall office lobby behaves like a much bigger room than its floor area suggests.
From estimate to order
Sonablock wood wool panels come in 600 x 600, 1200 x 600 and 2400 x 600 formats in 15 and 25 mm. For speech-frequency absorption per euro, the 25 mm panel is the default choice, reaching an absorption performance around alpha w 0.60 to 0.65 depending on specification and mounting. Order quantities work in full pallets, which is why the calculation above is worth doing before you buy: most rooms land surprisingly close to a clean pallet quantity.
Measure your room, run the numbers, and browse formats and colours in the wood wool acoustic collection. If you send us the room dimensions and a photo, we will sanity-check the estimate for free.