Wallace Sabine's formula estimates RT60 = 0.161 × V / A in metric units (V in m³, A in m² sabins) or RT60 = 0.049 × V / A in imperial units (V in ft³, A in ft² sabins). A is the sum of each surface area times its absorption coefficient.
- Measure each surface and look up its absorption coefficient.
- Multiply and add them up to get A.
- Divide 0.049 × V by A for RT60 in seconds.
- To hit a target, rearrange: A needed = 0.049 × V / target. Subtract what the room already has; that is what panels must add.
Sabine works best in rooms with fairly even absorption. For very absorbent rooms the Eyring formula is more accurate.