AudioCalcs
Absorption Coefficient Calculator — Room Absorption
Calculate total absorption and average absorption coefficient for a room from surface areas and material coefficients.
Walls
Floor
Ceiling
Acoustic Treatment (optional)
How We Calculate This
Total absorption A = Σ(S_i × α_i)
The total absorption is the sum of each surface area multiplied by its absorption coefficient.
Average α = A / S_total
The average absorption coefficient is the total absorption divided by the total surface area.
Frequently Asked Questions
A sabin is the unit of absorption equivalent to one square metre of perfectly absorptive surface (α = 1). Total absorption in sabins equals the sum of each surface area multiplied by its absorption coefficient. Named after acoustician Wallace Clement Sabine.
Concrete: 0.02, plasterboard wall: 0.05, glass window: 0.03, carpet on concrete: 0.30, heavy curtain: 0.55, 50mm acoustic foam: 0.50-0.80, 100mm rockwool panel: 0.80-0.95. Values vary significantly with frequency.
Total absorption (in sabins) is used in the Sabine equation to calculate RT60 reverb time: RT60 = 0.161 × V / A, where V is room volume and A is total absorption. Increasing absorption reduces reverb time.
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Last updated: February 2026
All calculations are estimates based on standard formulas. Always verify results for critical applications.