Tools · HUB · REV 2026-10-06
Calculators
A calculator here is a formula machine, not a decision machine. If the assumption written above it does not apply, the result is not used, however neat it looks.
What this gate is
RT60 by Sabine and Eyring for surfaces, sabins alone, incoherent level addition, a seat count from area, screen geometry, throw ratio, pixel distance by arcminute, and point-source level in a free field.
Each tool has a page that explains its limit, and this gate gathers them. Material coefficients are textbook-order buttons, to be replaced by a laboratory sheet.
What is published now
Acoustics
Acoustics
Seats
Seats
Image
Image
A fixed warning
A fixed warning
When to open this gate
To test how sensitive a number is
To test how sensitive a number is
To teach a team
To teach a team
Not to close a contractual dispute
Not to close a contractual dispute
How to read the subject
- 01
Read the formula.
- 02
Change one input and watch the result.
- 03
Write the assumption beside any figure you copy.
- 04
Stop the tool when a measurement or a code arrives.
What this gate does not do
Pasting the result into a bill of quantities
Pasting the result into a bill of quantities
Using the typical α as a product datum
Using the typical α as a product datum
Applying inverse square inside a live room
Applying inverse square inside a live room
RT60 · SABINE
Reverberation time
Formula used: RT = 0.161 V / A. A is area × absorption coefficient, plus audience sabins. The Eyring figure is surfaces only.
0.40 sabins/person is a common order of magnitude near 500 Hz for seated audience. Published ranges are wider. Change it when the project has data.
Material figures are mid-band textbook orders of magnitude, only to try the formula. Replace them with laboratory data and the real mounting.
A preliminary figure for understanding and comparison. Not a measurement, not an acoustic model, and not something to paste into a specification or a quotation.
Σ dB
Adding sound levels
L = 10 log₁₀( Σ 10^(Li/10) ). Incoherent power addition. It does not add phase-coherent sources, and it does not apply A-weighting unless the inputs already are.
A preliminary figure for understanding and comparison. Not a measurement, not an acoustic model, and not something to paste into a specification or a quotation.
SEATS
Preliminary seat count
Count = floor of net area ÷ (seat centre × row spacing), then wheelchair spaces are subtracted so they are not counted twice. This is not an egress calculation, a sightline study, or a local code.
A preliminary figure for understanding and comparison. Not a measurement, not an acoustic model, and not something to paste into a specification or a quotation.
SCREEN GEOMETRY
Screen geometry
Converts diagonal and aspect ratio into width and height. The 4× and 6× image-height distances are old rules of thumb for general image and text, not the AVIXA DISCAS method.
A preliminary figure for understanding and comparison. Not a measurement, not an acoustic model, and not something to paste into a specification or a quotation.
THROW RATIO
Throw ratio
Throw ratio = lens-to-screen distance ÷ image width. Fill two fields and the third is calculated. Lens shift, screen curve, and image brightness are not calculated.
A preliminary figure for understanding and comparison. Not a measurement, not an acoustic model, and not something to paste into a specification or a quotation.
PIXEL PITCH
Estimated viewing distance
The distance at which a pixel subtends one arcminute is about pixel pitch in millimetres × 3.44 metres. At two arcminutes the distance is about half. This is a geometric acuity limit, not a manufacturer recommendation, and video content is often accepted closer than the pixel-blend distance.
A preliminary figure for understanding and comparison. Not a measurement, not an acoustic model, and not something to paste into a specification or a quotation.
SPL
Level at a distance
Lp2 = Lp1 + 20 log₁₀(r1 / r2). A point source in a free field. It ignores the room, directivity, arrays, air absorption, and the sum of more than one source.
A preliminary figure for understanding and comparison. Not a measurement, not an acoustic model, and not something to paste into a specification or a quotation.
INVERSE SQUARE
Inverse square
Lp2 = Lp1 + 20 log₁₀(r1 / r2). A point source in a free field. It ignores the room, directivity, arrays, air absorption, and the sum of more than one source.
A preliminary figure for understanding and comparison. Not a measurement, not an acoustic model, and not something to paste into a specification or a quotation.
SABINS
Sabins
A = Σ (area × α) + people × sabins per person. The coefficient must come from a laboratory report for the product and its mounting, not from this typical table.
0.40 sabins/person is a common order of magnitude near 500 Hz for seated audience. Published ranges are wider. Change it when the project has data.
Material figures are mid-band textbook orders of magnitude, only to try the formula. Replace them with laboratory data and the real mounting.
A preliminary figure for understanding and comparison. Not a measurement, not an acoustic model, and not something to paste into a specification or a quotation.
Questions designers and owners ask
Is the calculator enough to design?
Is the calculator enough to design?
Why Sabine and Eyring together?
Why Sabine and Eyring together?
Are my calculations saved?
Are my calculations saved?
Where is a single tool?
Where is a single tool?
Is there an egress-code calculator?
Is there an egress-code calculator?
Technical sources
- The metric Sabine formula
The metric Sabine formula
- Arcminute geometry
Arcminute geometry
- AVIXA DISCAS
AVIXA DISCAS
Last editorial review: 2026-10-06. Review means the text was checked, not that a project was measured.
Turn the question into a brief
A study starts from room volume, use, and existing condition, not from a product name. Fill the brief and copy it.
Project study form