Audio Equalizer Calculator

Peaking EQ (Biquad). Enter sample rate, center frequency, gain (dB), and Q to get normalized coefficients instantly.

How to Use

  1. Choose your sample rate (e.g., 48000 Hz).
  2. Enter the center frequency (Hz) for the boost/cut.
  3. Set gain in dB (positive boosts, negative cuts).
  4. Enter Q (higher = narrower band). Optional: switch the input mode to bandwidth if you prefer.
  5. Copy or share coefficients for your DSP / plugin / embedded filter.
Inputs
All math is computed client-side. Results are normalized by a0.
Common: 44100, 48000, 96000
Must be > 0 and < sampleRate/2
Boost (+) or cut (−). Example: +3, −6
Typical: 0.5–4.0 (0.707 = “butter-ish” feel)
Enabled when Bandwidth mode is on

Coefficients (Normalized)

Output is normalized by a0, so a0 = 1.

b0
—
b1
—
b2
—
a1
—
a2
—
a0
1
Enter values to compute coefficients.
Formatting is client-side. API is optional for validation/export.
Show Work (step-by-step)
—
Work uses standard peaking EQ biquad terms (w0, alpha, A). Coefficients are normalized by a0.

Reference

This tool computes a peaking EQ biquad filter. You’ll typically use it in an IIR form like: y[n] = b0*x[n] + b1*x[n−1] + b2*x[n−2] − a1*y[n−1] − a2*y[n−2]

  • Sample rate (Hz): system DSP rate (e.g., 48 kHz)
  • Center frequency (Hz): where boost/cut peaks
  • Gain (dB): positive boost or negative cut
  • Q: bandwidth shape control (higher = narrower)
Tip: Always ensure f0 < sampleRate/2 (Nyquist).

FAQ

What’s the difference between Q and bandwidth?

Q is a “shape” parameter. Bandwidth (often in octaves) is another way to describe how wide the affected range is. This tool can work in either input style, but it always outputs the same biquad coefficients.

Why are coefficients “normalized”?

Many implementations divide all coefficients by a0 so that a0 = 1. That’s what you see here.

Can I use this for a notch filter?

A deep negative gain with a high Q behaves notch-like, but a true notch biquad is a different filter type. Use a dedicated notch biquad tool when precision matters.

Tool Info

Last updated:

Updates may include improved formatting presets, edge-case handling, and additional export formats.