What standard does this follow?

IEC 61260-1:2014 (and its predecessor ANSI S1.11), which defines the exact base-2 geometric series for both octave and 1/3-octave band filters.

What is the formula for band limits?

For an octave band: lower = fc / 2^(1/2), upper = fc × 2^(1/2). For a 1/3-octave band: lower = fc / 2^(1/6), upper = fc × 2^(1/6). The bandwidth ratio equals 2^(1/b) where b is 1 or 3.

Why do nominal center frequencies differ from exact values?

Nominal values (e.g. 1000 Hz, 125 Hz) are rounded reference labels used on instrument panels. The exact geometric center frequencies computed from the IEC series differ slightly but are used in filter design.

How many 1/3-octave bands are there in the audible range?

There are 31 standard 1/3-octave bands from 20 Hz to 20 kHz, or 33 if the 16 Hz and 25 kHz edge bands are included.

What is the bandwidth of each octave band?

An octave band spans a 2:1 frequency ratio. The -3 dB bandwidth is approximately 70.7 % of the center frequency (fc × 0.707 on each side). A 1/3-octave band spans a 2^(1/3):1 ratio, giving about 23 % bandwidth.

Octave Band Calculator

Name: Octave Band Calculator
Availability: InStock
Author: Nham Vu

Enter a center frequency or pick a standard band to get exact upper and lower limits for octave and 1/3-octave bands per IEC 61260.

Band Settings

Band Type

Custom Center Frequency (Hz)

Finds the nearest standard band for your input.

Standard Frequency Bands

1/3 Octave

Nominal (Hz)	Center (Hz)	Lower (Hz)	Upper (Hz)	BW (Hz)

Click any row to see full band details. Values per IEC 61260-1.

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Summary

Enter a center frequency or pick a standard band to get exact upper and lower limits for octave and 1/3-octave bands per IEC 61260.

How it works

Select octave or 1/3-octave band resolution from the Band Type dropdown.
Click any row in the frequency table to highlight that band.
Or type a custom center frequency to find the nearest standard band and see its exact limits.
The upper limit equals the center frequency multiplied by 2^(1/2) for octave bands.
The lower limit equals the center frequency divided by 2^(1/2) for octave bands.
For 1/3-octave bands the factor is 2^(1/6) applied to each edge.

Use cases

Set filter center frequencies on a real-time analyzer (RTA) or noise meter.
Design sound-absorbing panels tuned to specific octave bands.
Configure equalizer bands for room acoustics and studio treatment.
Verify band-pass filter specifications in audio equipment datasheets.
Perform occupational noise assessments across standard ISO bands.
Support architectural acoustics calculations for reverberation time (T60).
Calibrate speaker crossover frequencies to octave-aligned boundaries.
Check environmental noise compliance reports against standard band data.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu