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Filter Bandwidth and Q Calculator
Interpret a frequency band from its lower and upper edges: find geometric center, bandwidth, Q and octave width.
Lower edge (Hz): 20–20000; Upper edge (Hz): 20–20000
Inputs stay on this page and clear on refresh.
Filter Bandwidth and Q Calculator
Lower edge (Hz): 500 Upper edge (Hz): 2000
- Geometric center (Hz)
- 1000.000000
- Bandwidth (Hz)
- 1500.000000
- Geometric Q
- 0.666667
- Width (octaves)
- 2.000000
Use two positive band edges measured or specified at the same reference level. Require 20 ≤ lower < upper ≤ 20000 Hz. Bandwidth = upper−lower; geometric center = √(lower×upper); Q = center/bandwidth; octave width = log₂(upper/lower). Example: 500–2000 Hz gives center 1000 Hz, bandwidth 1500 Hz, Q 0.666667 and 2 octaves. Results show six decimals. This geometric band model does not design a filter or predict its response. Enter half-power edges only when the specification defines them that way; a peaking EQ’s gain, filter order, digital warping and manufacturer Q conventions can change the relationship to its controls. Confirm the actual response by measurement or documentation.
Methodology
How it works
Use two positive band edges measured or specified at the same reference level. Require 20 ≤ lower < upper ≤ 20000 Hz. Bandwidth = upper−lower; geometric center = √(lower×upper); Q = center/bandwidth; octave width = log₂(upper/lower). Example: 500–2000 Hz gives center 1000 Hz, bandwidth 1500 Hz, Q 0.666667 and 2 octaves. Results show six decimals. This geometric band model does not design a filter or predict its response. Enter half-power edges only when the specification defines them that way; a peaking EQ’s gain, filter order, digital warping and manufacturer Q conventions can change the relationship to its controls. Confirm the actual response by measurement or documentation.
Method and assumptions documented by Techrider.live
2026-10-17
Frequently asked questions
Can I copy this Q directly to every equalizer?
No. This Q is defined as geometric center divided by edge-to-edge bandwidth. Manufacturer and filter conventions vary, especially for peaking EQ. Use matching edge definitions and verify the actual device response.