Reverberation time (RT60) calculator
Estimate RT60 in six octave bands from your room's dimensions and surface materials — Sabine and Eyring, side by side — and see how much treatment closes the gap to your target.
Coefficients are typical published values — fine for planning; use manufacturer data for critical work. Below ~250 Hz the room is modal and RT60 is only part of the story: see the room mode calculator.
| Band | 125 | 250 | 500 | 1k | 2k | 4k |
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What RT60 means
RT60 is the time sound takes to decay by 60 dB after the source stops. Long RT60 makes rooms feel lively but smears detail; short RT60 sounds controlled but can feel dead. Different uses have different sweet spots, which is why the tool shows a target band rather than one number.
The formulas
Sabine: T = 0.161 · V / A where V is room volume (m³) and A = Σ Sᵢ·αᵢ is total absorption in sabins (m²).
Eyring: T = 0.161 · V / (−S · ln(1 − ᾱ)) where S is total surface area and ᾱ the area-weighted mean coefficient. Sabine assumes weak absorption and overestimates decay in well-treated rooms; Eyring stays accurate as rooms get deader. When the two diverge, trust Eyring.
How the treatment suggestion works
The tool computes how many square meters of high-performance absorption (α ≈ 0.95 midband, e.g. 100 mm mineral-wool panels) would bring the 500 Hz Sabine estimate to the middle of your target range: ΔA = 0.161·V/T_target − A_current. It replaces wall area rather than adding phantom surface, so the estimate stays physical.
FAQ
Why do my 125 Hz numbers look optimistic?
Statistical formulas assume a diffuse sound field, which small rooms don't have at low frequencies — modal behavior dominates there. Treat the low-band figures as rough indicators and plan bass control with modes in mind.
Sabine and Eyring disagree — which is right?
For mean absorption under ~0.2 they nearly agree. Above that, Sabine reads high; Eyring's logarithm handles absorbent rooms correctly. Studios and treated rooms should read the Eyring row.
Do people and furniture count?
Yes — a sofa is a decent bass absorber and every person adds roughly 0.4–0.5 sabins midband. This v1 keeps the model to surfaces; add a rug/curtain via the treatment row to approximate furnishings.