Enter the room size, how absorbent the bare room is, your target RT60, and the panel size and absorption coefficient (α or NRC).
Room Acoustic Treatment Calculator
Reverberation time (RT60) of a room and how many acoustic panels you need to reach a target, using the Sabine formula.
The Acoustic Treatment Calculator answers “how many acoustic panels do I need?” It estimates the room’s current reverberation time (RT60) with the Sabine formula, then calculates how much extra absorption — and how many panels of your size and rating — bring it down to your target.
Formula
Sabine: RT60 = 0.161 × V ÷ A (metric) or 0.049 × V ÷ A (feet)
A = S × ᾱ
Panels = ⌈(Aₜₐᵣᵍₑₜ − A) ÷ (panel area × (αₚₐₙₑₗ − ᾱ))⌉
Where:
- V = room volume
- S = total surface area (floor, ceiling, walls)
- ᾱ = average absorption of the bare room
- A = absorption in sabins; Aₜₐᵣᵍₑₜ = 0.161 × V ÷ target RT60
How the Calculation Works
Step 1: Compute volume and total surface area from the room dimensions.
Step 2: Current absorption = surface × average α; current RT60 from Sabine.
Step 3: Find the absorption needed for the target RT60.
Step 4: Each panel adds its area × (panel α − surface α) because it covers surface that was already absorbing a little.
Variables Explained
| Input | Meaning |
|---|---|
| Average absorption (α) | 0 = fully reflective, 1 = fully absorbent. Hard bare rooms are around 0.05–0.1; furnished rooms higher |
| Target RT60 | Seconds for sound to decay by 60 dB; shorter for studios, longer for living spaces |
| Panel absorption | From the panel’s test data (α or NRC) |
Example Calculation
Given: 20 × 15 × 9 ft room, α = 0.10, target 0.5 s, 2 × 4 ft panels with α = 0.9
- V = 2,700 ft³; S = 600 + 630 = 1,230 ft²
- Current absorption = 123 sabins; RT60 ≈ 0.049 × 2,700 ÷ 123 ≈ 1.08 s
- Needed = 0.049 × 2,700 ÷ 0.5 ≈ 265 sabins; extra ≈ 142
- Each panel adds 8 × (0.9 − 0.1) = 6.4 → 142 ÷ 6.4 = 22.2 → 23 panels
Engineering Assumptions
- Sabine’s formula works best for rooms with moderate absorption spread fairly evenly.
- Absorption coefficients vary with frequency; NRC is an average across mid frequencies. Thin panels do little in the bass — thicker panels or corner bass traps are needed there.
- Placement (first reflection points, corners, ceiling) matters as much as quantity.
Frequently Asked Questions
How many acoustic panels do I need?
Enough to add the absorption that brings RT60 to your target — the calculator works it out from your room and panel data.
What is RT60?
The time for sound to fall by 60 dB after the source stops.
What is a good RT60 for a home studio?
Short targets are usually used for mixing rooms; enter the target you are aiming for and check the result by measurement.
What is NRC?
Noise Reduction Coefficient — a single-number average of a material’s absorption at mid frequencies.
Do acoustic panels soundproof a room?
No — they reduce echo inside the room; blocking sound transmission needs mass, isolation and sealing.