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A resonant filter's bandwidth describes the range of frequencies it passes at or above half power, directly linked to its resonant frequency and Q factor. This calculator solves for whichever value — resonant frequency, Q factor, or bandwidth — is missing.
How it works
Enter any 2 of the 3 values (resonant frequency, Q factor, or bandwidth) and leave the one you want to solve for blank. The calculator applies BW = f₀/Q.
- Enter resonant frequency, f₀ (Hz) — leave blank to solve for this.
- Enter q factor — leave blank to solve for this.
- Enter bandwidth (Hz) — leave blank to solve for this.
- Click Calculate to see your results.
Examples
A moderately selective filter
A filter resonating at 1000 Hz with a Q factor of 10 has a bandwidth of 100 Hz — it passes frequencies roughly from 950 Hz to 1050 Hz at or above half power.
Who should use it
- Electronics coursework on filter design and resonance.
- Designing radio tuning or selective filter circuits to a target bandwidth.
Industry applications
- Electronics and RF circuit design
- Radio and communications engineering
Advantages
- Solves for any of the three variables, not just forward bandwidth calculation.
- Simple, direct relationship linking resonance sharpness to passband width.
Limitations
- Assumes an idealized single-resonance filter response — more complex multi-pole filter designs need more advanced analysis.
Common mistakes to avoid
- Confusing bandwidth with the resonant frequency itself — bandwidth describes the width of the passband, not its center.
- Forgetting bandwidth and Q are inversely related — a "bigger Q" always means a "smaller bandwidth," not the other way around.
Best practices
- Use this calculator together with the Q Factor or Parallel RLC Q Factor Calculator to translate between component values and the resulting bandwidth.
- Remember this describes the half-power (-3dB) bandwidth specifically, a standard but not the only possible bandwidth definition used in engineering.
Tips
- If you have a target bandwidth in mind, solve for the required Q factor first, then work backward to the component values using the Q Factor Calculator.