EQ Octave Band Calculator
Octave band analysis is the foundation of acoustic measurement and equalization. Standard 1-octave and 1/3-octave bands are defined by IEC 61260 and used on graphic equalizers, room acoustic analyzers, and spectrum displays. Enter a center frequency and select 1/1 octave or 1/3 octave to see the lower edge, upper edge, and bandwidth in Hz and in octaves. You can also generate the full standard octave band table from 20 Hz to 20 kHz.
Octave band formula
For n = band divisor (1 for 1/1 oct, 3 for 1/3 oct):
f_lower = f_center / 2^(1/(2n))
f_upper = f_center * 2^(1/(2n))
Bandwidth = f_upper - f_lower
Q = f_center / Bandwidth
For a full octave (n=1), f_upper / f_lower = 2^(1/1) = 2. For a third octave (n=3), f_upper / f_lower = 2^(1/3) = 1.2599. The geometric center is the square root of f_lower * f_upper.
Standard 1/1-octave band centers (IEC 61260)
- 31.5 Hz, 63 Hz, 125 Hz, 250 Hz, 500 Hz
- 1,000 Hz, 2,000 Hz, 4,000 Hz, 8,000 Hz, 16,000 Hz
- Each band spans exactly one octave (upper = 2 * lower).
- 1/3-octave bands from 20 Hz to 20 kHz: approximately 30 bands total.
EQ octave bands: frequently asked questions
What is an octave band?
An octave band is a frequency range where the upper frequency limit is exactly double the lower frequency limit. The center frequency is the geometric mean: sqrt(f_lower * f_upper). Standard octave band center frequencies start at 31.5 Hz and double each band: 63, 125, 250, 500, 1k, 2k, 4k, 8k, 16k Hz.
What are 1/3-octave bands?
One-third octave bands divide each octave into three equal ratios. The frequency ratio between adjacent 1/3-octave centers is 2^(1/3) = 1.2599. There are approximately 30 standard 1/3-octave bands from 20 Hz to 20 kHz. They give finer frequency resolution than full-octave bands.
How is EQ bandwidth (Q) related to octaves?
For a parametric EQ, Q and bandwidth in octaves are related: BW (octaves) = log2(f_upper / f_lower). High Q = narrow bandwidth. Q = 1.414 (sqrt(2)) corresponds to approximately 1 octave. Q = 4.31 is approximately 1/3 octave.
What are the standard 1/1-octave band center frequencies?
Standard 1/1-octave centers (IEC 61260): 31.5, 63, 125, 250, 500, 1,000, 2,000, 4,000, 8,000, and 16,000 Hz. These are the frequencies marked on most graphic equalizers.
Why does professional audio use 1/3-octave resolution?
Human hearing can distinguish frequency changes of about 1/20th of an octave in the midrange, so 1/3-octave provides enough resolution for room acoustic analysis without being so detailed as to be impractical. Room modes and resonances are often measured at 1/3-octave resolution.
Official sources
- IEC 61260: iec.ch - Electroacoustics: Octave-Band and Fractional-Octave-Band Filters standard.
- Audio Engineering Society (AES): aes.org - EQ and acoustic measurement standards.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.