EQ Frequency Calculator — Q Factor & Bandwidth Converter

Q (quality factor) defines the width of an EQ band. A higher Q means a narrower, more surgical cut or boost. A lower Q means a wider, more gentle shape. Q = centre frequency / bandwidth. A Q of 1.41 is approximately 1 octave wide, Q of 4.32 is 1/3 octave.

For broad tonal shaping: Q 0.5-1.5 (1-2 octaves). For corrective EQ: Q 2-8 (narrow cuts). For notch filtering: Q 10-30 (very narrow). Low Q values sound more natural and musical, high Q values are surgical but can sound unnatural if overused.

They are inversely related — wider bandwidth (more octaves) means lower Q. 1/3 octave = Q 4.32, 2/3 octave = Q 2.14, 1 octave = Q 1.41, 2 octaves = Q 0.67. The exact conversion uses: Q = sqrt(2^N) / (2^N - 1) where N is octaves.

Bandwidth is the frequency range between the -3 dB points either side of the centre frequency, where the centre sits at the geometric mean of the two bounds. For a 1 kHz centre at exactly 1 octave (Q = 1.414), the lower -3 dB point is 1000/√2 = 707.1 Hz and the upper is 1000×√2 = 1414.2 Hz, so the bandwidth is 1414.2 − 707.1 = 707.1 Hz. Q = centre / bandwidth = 1000/707.1 = 1.414.