Band EQ Frequency Calculator
Compute how far a bell, high-pass, low-pass or shelf EQ band reaches from its centre frequency, given Q and gain. Use it when setting up an equaliser in a mix or mastering session.
Last updated: September 2026
Formula below · 2 sources (aes.org, Wikipedia) · Updated Sep 2026
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About this calculator
Equalisation shapes the tonal balance of audio by boosting or cutting specific frequency regions. A bell (peaking) band always peaks at its centre frequency f_c; Q sets its width, Q = f_c / bandwidth, with the band edges placed symmetrically on a log scale (f_low × f_high = f_c²). For a bell this calculator returns the upper band edge: f_high = f_c × (√(1 + 1/(4Q²)) + 1/(2Q)). A higher Q means a narrower, more surgical cut or boost. For high-pass and low-pass filters the corner (cutoff) frequency is the frequency you set; Q changes the shape and any resonant bump near the corner, not the corner itself, so the result equals the centre frequency. For shelf filters the calculator returns f_c × 10^(|gain| / 40), a rough guide to where the shelf approaches its full gain. These relationships help you predict where your EQ changes will actually take effect before you commit them to a mix, avoiding frequency masking and harsh resonances.
How to use
For a bell EQ boost: centre frequency = 1,000 Hz, Q = 2, gain = +6 dB. The boost peaks at 1,000 Hz. Apply the band-edge formula: f_high = 1,000 × (√(1 + 1/16) + 1/4) = 1,000 × (1.0308 + 0.25) ≈ 1,281 Hz, and the lower edge is 1,000² / 1,281 ≈ 781 Hz, a 500 Hz-wide band (1,000 / 2 = 500). Raise Q to narrow the band around the 1,000 Hz centre.
Frequently asked questions
What Q factor should I use for surgical EQ cuts when removing resonances?
For surgical removal of harsh resonances or feedback frequencies, a Q between 5 and 20 is typical — the higher the Q, the narrower and more precise the cut. A Q of 10 at 2 kHz, for example, affects roughly a 200 Hz band, leaving surrounding frequencies untouched. Start with a narrow Q and a deep cut (up to −12 dB), sweep the frequency to find the offending resonance, then raise the gain back to the minimum effective cut. Overly wide cuts at high Q values can introduce phase artefacts, so use them sparingly.
How does Q factor relate to bandwidth in octaves for a parametric EQ?
Q and bandwidth in octaves (BW) are related by: 1/Q = 2 × sinh(ln(2)/2 × BW), so BW = (2/ln 2) × asinh(1/(2Q)) ≈ 1.44/Q for narrow bands. A Q of 1.41 (√2) gives a 1-octave bandwidth, which is a musical, broad-brush boost or cut. A Q of 0.7 gives about 2 octaves — suitable for tonal shaping — while a Q of 4 gives about a third of an octave for precise corrections. Many DAW EQ plug-ins display bandwidth in octaves alongside Q, so understanding the relationship helps you translate between different EQ interfaces.
When should I use a bell EQ versus a shelf EQ in a mix?
Use a bell (peaking) EQ when you need to address a specific frequency range, such as adding presence to a vocal around 3–5 kHz or reducing muddiness around 300 Hz in a guitar. Bell bands are precise and have minimal effect outside their bandwidth. Use a shelf EQ to make broad, gentle tonal changes — for example, adding air to a mix with a high shelf boost above 10 kHz, or reducing low-end rumble with a low shelf cut below 80 Hz. In mastering, shelves are preferred because they alter tonality smoothly without introducing narrow resonant peaks that can sound unnatural on a wide range of playback systems.