Room Mode Calculator
Estimate the low-frequency resonances of a rectangular room. Enter its dimensions, inspect the mode frequencies and export the list for comparison with measurements.
Use internal room dimensions, each 0.5–20 m (1.64–65.62 ft). The default 343 m/s is an approximation near 20 °C. No microphone is used. This is a frequency estimate, not an acoustic measurement.
Read the frequencies as candidates to investigate
An unusually loud bass note may come from a room resonance, the speaker, its placement or the recording. This tool lists the ideal room’s natural frequencies. It does not predict how loud any mode will be at your seat. The room-mode guide works through a 4 × 3 × 2.5 m example and explains how to compare the list with measurements.
Enter dimensions inside the room, between opposing boundaries. Selecting feet changes how the numbers are interpreted; enter the dimensions again in the selected unit. Decimal feet are not feet-and-inches notation: 8 feet 6 inches is 8.5 feet. Retain the same sound speed when comparing two dimension choices.
The rectangular-room equation
Each mode has three integer orders, one for length, width and height. Its frequency is c/2 × √((nL/L)² + (nW/W)² + (nH/H)²), where c is sound speed in metres per second and dimensions are in metres. The all-zero case is excluded. One nonzero order gives an axial mode; two give a tangential mode; three give an oblique mode. The Sengpiel Audio calculator documents the same rectangular-room model.
At 343 m/s, a four-metre dimension has its first axial mode at 42.875 Hz. A three-metre dimension gives 57.167 Hz, and 2.5 m gives 68.6 Hz. Equal frequencies can represent different patterns, so the CSV preserves every mode. The chart separates mode types vertically; its vertical axis is not a decibel scale.
Use the result with its limits
Sloped ceilings, large openings, flexible walls and coupled rooms break the simple boundary assumptions. Surface absorption and source/listener positions also change the response. A mode list cannot specify treatment thickness, reverberation time or an ideal seat. The Room EQ Wizard simulator documentation shows why modelling positions and losses requires additional information.
The tone generator can provide a quiet listening reference, but a browser output level is not calibrated sound pressure. Do not raise a tone to compensate for a quiet frequency. For musical context, compare a candidate frequency with the note table and the harmonic series.
Export a comparison you can repeat
Calculate after changing the inputs. Download CSV for all calculated modes; the visible table stops after 200 rows. The export records dimensions, sound speed and the frequency ceiling. Copy results gives a shorter summary. Save both the assumptions and any separate measurement conditions so a later comparison has a defined basis.
Questions
Does this measure my room?
No. It predicts frequencies for an ideal rectangular room with rigid walls. It does not measure frequency response, sound pressure, decay, absorption or speaker placement. Use suitable measurement equipment and an acoustics professional when the decision requires it.
Why can two rows have the same frequency?
Different mode patterns can share a frequency, particularly when room dimensions match or have simple ratios. The list retains each pattern instead of hiding it in a single row.
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