Room Acoustics Calculator
Calculate reverberation time (RT60) and acoustic properties of your room. Enter room dimensions and surface materials to optimize sound quality for recording studios, home theaters, or music rooms.
- RT60 (Reverberation Time): Time for sound to decay by 60 dB after the source stops
- Shorter RT60 (0.2-0.4s): Better for speech clarity and recording (dead/dry sound)
- Longer RT60 (0.5-0.8s): More natural reverb for music and concerts (live sound)
- Formula Used: Sabine’s formula — RT60 = 0.161 × V / A (V = volume, A = absorption)
- Absorption Coefficient: 0.0 = total reflection, 1.0 = total absorption
This Room Acoustics Calculator estimates reverberation time from your room dimensions and the sound-absorption properties of its main surfaces. Enter the length, width and height, then review the floor, ceiling and wall coefficients for each frequency band. The results compare Sabine and Eyring estimates from 125 Hz to 4 kHz, helping you see how the room’s predicted decay changes with frequency.
Use the results as a planning estimate, not as a substitute for measuring a finished room. If you only need a direct reverberation-time calculation with individually entered surfaces, use our RT60 Calculator. If you want to focus on how individual materials contribute to total absorption, the Absorption Coefficient Calculator is the more targeted tool.
How to Use the Room Acoustics Calculator
- Choose your units. Select metres or feet. The calculator converts the dimensions when you switch units.
- Enter the internal room dimensions. Use the room’s inside length, width and height rather than exterior building measurements.
- Review the surface areas. The calculator derives the floor, ceiling and four-wall areas from the dimensions you entered.
- Enter frequency-specific absorption coefficients. Replace the example values with data appropriate to the actual material, thickness, mounting and frequency. The sample numbers are placeholders, not verified product specifications.
- Compare the results. Review the RT60 estimates at each band, the mean at 500 Hz and 1 kHz, and the comparison with the selected illustrative target.
Count each part of the room boundary only once. If an acoustic panel covers part of a wall, treat that area as panelled area and reduce the area assigned to the original wall finish. Otherwise, the same physical area would be counted twice and the predicted absorption would be too high.
Understanding Axial Room Modes
The axial-mode table estimates the first four harmonics associated with the room’s length, width and height. These frequencies can help flag potential low-frequency resonances that are determined by room dimensions. A calculated mode frequency does not tell you how strong a resonance will be at a particular seat, and it does not replace measurement or a fuller acoustic analysis.
Room modes and reverberation time describe different aspects of room acoustics: RT60 estimates the overall decay of sound, while axial modes identify frequencies that may be reinforced or reduced by the room geometry. Consider both when planning a listening room or studio.
How Room Volume and Surface Area Are Calculated
For a rectangular room, volume is length × width × height. The total boundary surface area is twice the sum of the floor/ceiling area, the two long-wall areas and the two short-wall areas. These geometric values are the basis for the absorption and reverberation calculations.
For each frequency band, the equivalent absorption area is calculated by multiplying each surface’s area by its absorption coefficient and adding the contributions:
A = Σ (Sᵢ × αᵢ)
Here, Sᵢ is a surface area and αᵢ is its absorption coefficient for that band. Coefficients vary with frequency, so a material that absorbs mid- and high-frequency sound effectively may absorb less at low frequencies. See our guide to sound absorption coefficients when selecting appropriate input data.
Sabine vs. Eyring: Why the Calculator Shows Both
The Sabine equation estimates reverberation time using room volume and total equivalent absorption area. In metric units, its common form is RT60 = 0.161 × V ÷ A; the corresponding imperial form uses the constant 0.049 with cubic feet and square-foot sabins. The units and constant must match.
The Eyring equation uses room volume, total surface area and the area-weighted mean absorption coefficient: RT60 = 0.161 × V ÷ [−S × ln(1 − ᾱ)] in metric units. It can be more suitable when average absorption is higher. Read the detailed explanations of the Sabine formula and Eyring formula for their assumptions and limitations.
Neither equation models every acoustic effect. Both are statistical estimates and can be less reliable in small rooms, at low frequencies, or where absorption is unevenly distributed. They do not identify room modes, flutter echo, speaker-placement problems or the exact effect of furniture and occupants.
Choosing and Interpreting an RT60 Target
The target selector is a general comparison aid, not a universal pass/fail standard. A useful reverberation time depends on room size, intended use, frequency, background noise and the balance between clarity and liveliness. A speech-focused room, a control room and a performance space do not necessarily need the same decay time. Treat the selected target as a starting point and verify the requirements for your specific room.
If your estimate is longer than you want, compare realistic changes to absorptive finishes and treatment coverage, then recalculate. Do not assume that adding thin panels will solve low-frequency problems: low-frequency behaviour often depends on room dimensions and the design and placement of the treatment.
Common Input Mistakes
- Using generic coefficients as if they were measured data: absorption depends on frequency, mounting, thickness and the test conditions.
- Mixing units: keep dimensions and the formula constant consistent. This calculator converts its internal geometry for the selected unit system.
- Double-counting treatment: avoid adding a panel’s area on top of the wall area it replaces.
- Assuming one average value describes every frequency: compare the band-by-band results, especially if low-frequency behaviour matters.
- Treating a prediction as a measurement: the calculator does not record sound or measure an impulse response.
For the site’s broader collection of tools, visit the ReverbCalculator .
Frequently Asked Questions
Does this calculator measure the room with a microphone?
No. It calculates estimates from the dimensions and absorption coefficients you enter. It does not access a microphone or capture audio.
Why do the Sabine and Eyring results differ?
The equations model absorption differently. Their estimates may be similar in lightly absorptive rooms and diverge more as average absorption increases. The difference is a useful comparison, not proof that either estimate exactly matches a real room.
Why are absorption coefficients shown for six frequencies?
Absorption changes with frequency. The six bands provide a more informative estimate than using a single coefficient for the whole audible range, although they are still a simplified representation of room acoustics.
Are the suggested target times official standards?
No. They are illustrative values for quick comparison. Appropriate targets vary by room purpose, volume, applicable guidance and design requirements.
Why can the result be inaccurate in a small room?
Small rooms can have strong low-frequency resonances and non-diffuse sound fields. The Sabine and Eyring equations do not calculate individual room modes or every reflection, so real behaviour can differ from the predicted RT60.
Next step: Use the calculator to compare plausible material scenarios, then check the relevant formula and coefficient references before making treatment decisions. For a broader explanation of the assumptions behind these calculations, read how the room-acoustics calculators work.