Low Pass Filter Calculator
Calculate capacitor value for RC low pass filters
Hertz (Hz)
Ohms (Ω)
How to Use This Calculator
Enter Cutoff Frequency
Enter the desired cutoff frequency (3dB point) in hertz. Frequencies below this pass through.
Enter Resistance
Enter the resistor value in ohms. This forms the RC filter with the capacitor.
Get Capacitor Value
Click calculate to see the required capacitor value for the low pass filter.
Formula
fc = 1 / (2π × R × C)
C = 1 / (2π × R × fc)
Where:
- fc = Cutoff frequency (Hz)
- R = Resistance (Ω)
- C = Capacitance (F)
- π ≈ 3.14159
Example:
Cutoff Frequency = 1000 Hz, Resistance = 1000 Ω
C = 1 / (2 × π × 1000 × 1000) = 1 / 6,283,185 = 0.159 µF
About Low Pass Filter Calculator
The Low Pass Filter Calculator helps design RC low pass filters. Low pass filters allow frequencies below the cutoff to pass while attenuating higher frequencies. They're commonly used in audio circuits, power supply filtering, and signal processing.
When to Use This Calculator
- Audio Circuits: Remove high-frequency noise from audio signals
- Power Supply Filtering: Filter high-frequency ripple
- Signal Processing: Design filters for specific frequency ranges
- Educational Purposes: Learn about filter design
Why Use Our Calculator?
- ✅ Accurate Calculations: Uses correct filter formula
- ✅ Easy to Use: Simple interface
- ✅ Free Tool: No registration required
- ✅ Educational: Includes formulas and examples
Common Applications
Power Supply Filtering: Low pass filters remove high-frequency ripple and noise from power supply outputs, providing clean DC voltage.
Audio Systems: Low pass filters remove high-frequency noise and prevent aliasing in audio processing systems.
Tips for Accurate Results
- Enter frequency in hertz
- Enter resistance in ohms
- Cutoff frequency is the -3dB point
- Lower frequencies require larger capacitors
Frequently Asked Questions
What is a low pass filter?
A low pass filter allows frequencies below the cutoff frequency to pass through while attenuating frequencies above the cutoff. It's the opposite of a high pass filter.
What is the cutoff frequency?
The cutoff frequency (fc) is the frequency at which the filter's output is -3dB (approximately 70.7%) of the input. It's the boundary between passband and stopband.
How does it differ from high pass?
Low pass filters pass low frequencies and block high frequencies. High pass filters do the opposite - they pass high frequencies and block low frequencies.