Calculator
Example data table
| Room (m) | Use case | Total A (sabins) | RT60 Sabine (s) | Target range (s) |
|---|---|---|---|---|
| 6.0 × 4.0 × 2.7 | Speech / classroom | 40 | 0.65 | 0.50–0.90 |
| 4.0 × 3.0 × 2.4 | Podcast / voice booth | 55 | 0.34 | 0.20–0.40 |
| 7.0 × 5.0 × 3.2 | Home theater / cinema | 60 | 0.95 | 0.40–0.80 |
Examples are illustrative; furnishings and frequency strongly affect real outcomes.
Formula used
- Room volume: V = L × W × H
- Total surface area: S = 2(LW + LH + WH)
- Total absorption: A = Σ(areaᵢ × αᵢ)
- Sabine RT60: RT60 = k·V/A, where k = 0.161 (metric) or 0.049 (imperial)
- Eyring RT60: RT60 = k·V / (−S·ln(1−ᾱ)), with ᾱ = A/S
These are broadband estimates. For real design, evaluate octave bands and include seating, air absorption, and diffusion.
How to use this calculator
- Select your units, calculation method, and use case.
- Enter room dimensions to compute volume and surface area.
- Use Detailed surfaces to add areas and absorption coefficients.
- Press Calculate to see RT60 and target comparison.
- Download CSV for spreadsheets, or PDF for sharing.
Perfect reverb guide
1) What “perfect reverb” really means
“Perfect” reverb is the decay that matches your purpose. A lecture room needs clarity, while music spaces can be more spacious. This calculator estimates RT60 (seconds to drop 60 dB) so you can tune the room toward a practical target.
2) RT60 is the core number
RT60 summarizes how long sound energy lingers. If RT60 is 0.30 s, speech sounds tight and controlled; if it is 1.80 s, the room feels live and blended. Most small studios aim around 0.2–0.5 s, while larger halls can exceed 1.5 s.
3) Target ranges you can compare against
Use-case targets vary, but common starting points are: podcast/booth 0.20–0.40 s, control room 0.20–0.50 s, classroom 0.50–0.90 s, home theater 0.40–0.80 s, chamber music 0.80–1.40 s, and church/auditorium 1.50–2.80 s. The calculator compares your result to these ranges.
4) Volume changes what “ideal” feels like
Bigger rooms usually tolerate longer decay because reflections arrive later and disperse more. A 25 m³ bedroom often benefits from shorter times than a 250 m³ hall. That’s why the calculator lightly adjusts targets based on room size.
5) Sabine vs Eyring (why you see two results)
Sabine works well when average absorption is modest. Eyring handles higher absorption more smoothly using −S·ln(1−ᾱ). If your average ᾱ rises above roughly 0.20, Eyring often predicts a slightly longer, more realistic RT60.
6) “Sabins” and absorption coefficients
A surface contributes absorption area A = area × α. For example, 10 m² of carpet at α = 0.35 adds 3.5 sabins. Painted drywall might be near 0.03–0.07, heavy curtains can be around 0.35–0.60 (installation and frequency dependent).
7) Treatment planning with quick math
If RT60 is too long, increase A by adding panels, rugs, thick drapes, or upholstered seating. As a rough guide, increasing total A by 25% can reduce RT60 by about 20% (because RT60 scales inversely with A). If the room is too dry, reduce absorption or add diffusion.
8) Iterate, then export a report
Enter your surfaces, calculate, and tweak one change at a time (add a panel row, change curtain α, or adjust covered area). When the status shows In range, export CSV for spreadsheets or PDF for sharing with clients, installers, or your own build notes.
FAQs
1) What does RT60 mean?
RT60 is the time for sound level to drop by 60 dB after the source stops. Lower values sound tighter; higher values sound more reverberant and blended.
2) Which method should I choose?
Use Auto to see both. Sabine is fine for moderate absorption. Eyring is usually better when the room is heavily treated and the average absorption ᾱ is relatively high.
3) Do I need every surface to get a useful result?
No. Start with the big contributors: floor, ceiling, total wall area, and major treatments. Then add smaller items like curtains or seating to refine the estimate.
4) Why can my room measure differently than the calculator?
Real rooms vary by frequency, furnishings, air absorption, leakage, and diffusion. This tool is a broadband estimate. For accuracy, measure in octave bands and compare.
5) How do I estimate absorption coefficients?
Use manufacturer data when possible. If you don’t have it, choose conservative values and run sensitivity checks by trying a low and high α for the same surface.
6) What’s a quick way to shorten reverb?
Add absorption where reflections are strong: thick rug, panels at first reflection points, heavy curtains, and soft seating. Increasing total absorption A reduces RT60 roughly in proportion.
7) Is “perfect” reverb the same for all music?
No. Different genres and production styles prefer different decay times. Use the targets as a starting point, then adjust by listening tests and measurements in your specific space.