Band Stop Filter Calculator
Design a band-stop or notch filter to reject a specific frequency band.
About Band Stop Filter Calculator
A notch filter needs high Q to reject a narrow band without affecting nearby wanted signals. Mains hum rejection at 50 or 60 Hz is the most common application. Too low a Q removes wanted signal along with the interference, while too high a Q makes the notch sensitive to component drift and frequency variation.
Formula
Band Stop Filter
Notch frequency = √(f_L f_H); Q = f₀ ÷ stop bandwidth; C = 1 ÷ ((2πf₀)² L)
- notch
- Narrow band of frequencies strongly attenuated
- Q
- High Q gives a narrow notch
Worked example
With the default values below, Band Stop Filter Calculator returns Notch Centre Frequency of 49.749. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Lower cutoff frequencyminimum 0.01 Hz
- 45 Hz
- Upper cutoff frequencyminimum 0.02 Hz
- 55 Hz
- Signal frequencyminimum 0.01 Hz
- 50 Hz
- Inductance availableminimum 0 H
- 0.1 H
Results
- Notch Centre Frequency
- 49.749 Hz
- Stop Bandwidth
- 10.000 Hz
- Quality Factor
- 4.9749
- Capacitance for That Notch
- 0.000102344630 F
- Is the Signal Rejected
- Yes — the signal falls inside the stopband
Step by step
- 1Values used
- 2Band Stop Filter
- 3Notch Centre Frequency= 49.749 Hz
- 4Stop Bandwidth= 10.000 Hz
- 5Quality Factor= 4.9749
- 6Capacitance for That Notch= 0.000102344630 F
- 7Is the Signal Rejected= Yes — the signal falls inside the stopband
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or fees or charges into account.
- Figures are rounded for display to 12 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Band Stop Filter calculated?
Notch frequency = √(f_L f_H); Q = f₀ ÷ stop bandwidth; C = 1 ÷ ((2πf₀)² L) A notch filter needs high Q to reject a narrow band without affecting nearby wanted signals. Mains hum rejection at 50 or 60 Hz is the most common application.
Why does Band Stop Filter matter?
Too low a Q removes wanted signal along with the interference, while too high a Q makes the notch sensitive to component drift and frequency variation.
What values do I need to enter?
This calculator takes 4 inputs: Lower cutoff frequency, Upper cutoff frequency, Signal frequency, Inductance available. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.