Absorption Coefficient & RT60 Calculator
Calculate total room sound absorption, average absorption coefficient, and estimated reverberation time (RT60) using Sabine and Eyring formulas.
Surface Materials & Areas
| Surface / Material Description | Area (m²) | Absorption (α) | Subtotal (Sabins) | Action |
|---|
Calculate Sound Absorption and Estimate RT60 with Confidence
An absorption coefficient calculator helps estimate how much sound energy a room absorbs by combining the absorption values of individual surfaces. Instead of manually calculating the contribution of every wall, ceiling, floor, window, or acoustic panel, this tool automatically totals the room’s sound absorption, calculates the average absorption coefficient, and estimates reverberation time (RT60) using both the Sabine and Eyring equations.
The calculator supports both metric and imperial units, includes a library of common building materials, and allows you to add or remove custom surfaces as your room design changes. Whether you’re planning a recording studio, home theater, office, classroom, or listening room, it provides a fast mathematical estimate to guide acoustic treatment decisions.
How the Absorption Coefficient Calculator Works
Every surface in a room absorbs a different amount of sound.
The calculator determines the total room absorption using:
Total Absorption (A) = Σ (Surface Area × Absorption Coefficient)
Each surface contributes to the overall absorption based on its size and material. Once every surface has been added, the calculator determines the room’s average absorption coefficient:
Average Absorption (ᾱ) = Total Absorption ÷ Total Surface Area
Using those values, it calculates reverberation time with two established acoustic models:
- Sabine RT60 = (Constant × Room Volume) ÷ Total Absorption
- Eyring RT60 = (Constant × Room Volume) ÷ (−Total Surface Area × ln(1 − ᾱ))
The calculator automatically applies the appropriate constant for metric or imperial units and updates every result instantly as you edit the room.
If you only need a quick RT60 estimate from room dimensions, the dedicated RT60 Calculator provides a simpler workflow.
Understanding the Results
The calculator reports several values that describe how sound behaves in your room.
| Output | What It Represents |
|---|---|
| Sabine RT60 | Reverberation estimate using the Sabine equation |
| Eyring RT60 | Reverberation estimate using the Eyring equation |
| Total Absorption | Combined sound absorption of all surfaces (sabins) |
| Average Absorption Coefficient | Overall absorption efficiency of the room |
Sound absorption coefficients generally range from 0.0 (highly reflective materials such as concrete) to values approaching 1.0 (very absorbent materials such as deep fiberglass absorbers or open windows).
Because the calculator totals every surface automatically, you can quickly see how changing materials affects the overall acoustic response.
Sabine vs. Eyring RT60
The calculator provides both reverberation estimates because each equation is best suited to different acoustic conditions.
Sabine Formula
The Sabine equation is widely used for rooms with relatively low average absorption. It generally performs well when the room contains mostly reflective surfaces and the average absorption coefficient remains below approximately 0.3.
Eyring Formula
The Eyring equation accounts for higher overall absorption and typically produces shorter reverberation estimates in well-treated spaces. As more acoustic panels, bass traps, carpets, and absorptive finishes are added, the Eyring calculation often provides a more realistic prediction.
For a deeper explanation of reverberation targets, the Ideal RT60 article explains recommended decay times for different listening environments.
How to Use the Calculator
Using the calculator is straightforward.
- Choose Metric or Imperial units.
- Enter the room volume.
- Add each room surface to the table.
- Select a material or enter a custom absorption coefficient.
- Repeat until all major room surfaces have been included.
- Review the total absorption, average coefficient, and both RT60 estimates.
You can also add new rows for additional surfaces or delete rows as your design changes.
If you’re unsure about material values, the guide to Absorption Coefficients explains how different building materials affect sound absorption.
Practical Applications
This calculator is useful for many types of acoustic planning, including:
- Recording studios.
- Home theaters.
- Podcast rooms.
- Listening rooms.
- Classrooms.
- Offices.
- Conference rooms.
By comparing different material combinations, you can estimate how adding acoustic panels, carpets, curtains, or bass traps may influence reverberation before purchasing treatment.
For broader room planning, the Room Acoustics Calculator estimates room modes and surface area, while the Room Acoustics Guide explains how reflections, dimensions, and treatment work together.
Tool Limitations
This calculator provides mathematical estimates based on the room information you enter.
It does not:
- Measure a room using a microphone.
- Detect acoustic problems automatically.
- Replace professional acoustic measurements.
- Simulate furniture placement or speaker positioning.
- Predict every real-world reflection inside a room.
Actual reverberation time may differ because furniture, people, irregular room geometry, and treatment placement all influence acoustic performance.
For additional treatment advice, the guides on Acoustic Treatment, Bass Traps, and Home Studio Acoustics provide practical recommendations.
Frequently Asked Questions
What is an absorption coefficient?
An absorption coefficient describes how much sound energy a material absorbs. Values near 0 indicate highly reflective materials, while values approaching 1 represent highly absorbent surfaces.
Why does the calculator show both Sabine and Eyring RT60?
The Sabine equation is commonly used for rooms with relatively low average absorption, while the Eyring equation generally provides more realistic estimates for heavily treated rooms with higher average absorption.
What are sabins?
A sabin is a unit of total sound absorption. The calculator determines total absorption by multiplying each surface area by its absorption coefficient and then summing every surface.
Can I add my own materials?
Yes. The calculator allows you to add custom surfaces and specify your own absorption coefficient values for each one.
Does this calculator measure my room?
No. It performs mathematical calculations based entirely on the room dimensions, materials, and absorption values that you enter.