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Low Pass Filter Calculator

Low pass filter calculator is an easy-to-use tool to quickly determine the cutoff frequency of a low pass passive filter. A low pass filter removes higher-frequency components from a given AC signal.

Cutoff frequency of a low pass passive filter

This calculator allows you to choose filter circuit: RC filter or RL filter.

RC low pass passive filter

The RC low pass passive filter consists of a resistor and a capacitor.

Cutoff frequency formula: f_c = 1 / 2πRC

To calculate a particular parameter of a circuit (e.g. cutoff frequency (f_c), resistance (R) value or capacitance (C) value) click on the corresponding parameter on the figure and then enter all the necessary values:

If you specify resistance (R) value and capacitance (C) value the cutoff frequency will be calculated;
If you specify cutoff frequency (f_c) value and capacitance (C) value the resistance (R) value will be calculated;
If you specify cutoff frequency (f_c) value and resistance (R) value the capacitance (C) value will be calculated.

RL low pass passive filter

The RL low pass passive filter consists of a resistor and a inductor.

Cutoff frequency formula: f_c = R / 2πL

To calculate a particular parameter of a circuit (e.g. cutoff frequency (f_c), resistance (R) value or inductance (L) value) click on the corresponding parameter on the figure and then enter all the necessary values:

If you specify resistance (R) value and inductance (L) value the cutoff frequency will be calculated;
If you specify cutoff frequency (f_c) value and inductance (L) value the resistance (R) value will be calculated;
If you specify cutoff frequency (f_c) value and resistance (R) value the inductance (L) value will be calculated.

Frequently Asked Questions

How to Calculate the Cutoff Frequency of a Low-Pass Filter? Simple Examples

How to Calculate the Cutoff Frequency of a Low-Pass Filter? Simple Examples
1. Student Project: Signal Filtering in Lab In a basic electronics lab, students often need to analyze how a simple RC filter affects signals of different frequencies. With this setup, signals below ~1.6 kHz pass almost unchanged, while higher frequencies are attenuated. This helps students visualize frequency response, understand the concept of cutoff frequency, and prepare for more complex filter designs in advanced courses. R = 1 kΩ, C = 0.1 µF f_c = 1 / 2×π×1000×1.0×10^–7 ≈ 1592 Hz 2. Professional Use: Audio Crossover Audio engineers use low-pass filters to direct bass frequencies to subwoofers while blocking mids and highs. For example, in a speaker crossover network, this RC filter ensures only frequencies below ~154 Hz reach the bass driver. Using the calculator helps professionals quickly test different resistor and capacitor values during design, saving time and ensuring high-quality sound reproduction without distortion. R = 2.2 kΩ, C = 0.47 µF f_c = 1 / 2×π×2200×4.7×10^–7 ≈ 154 Hz 3. Home / DIY: Power Supply Ripple Filtering In household electronics or DIY projects, one common problem is residual AC ripple in a DC power supply. By choosing a large capacitor and small resistor, this low-pass filter attenuates unwanted ripple (usually at 50/60 Hz) while letting the DC voltage through. The calculator helps DIY hobbyists select optimal capacitor sizes, avoiding hum in audio devices, flicker in LED lights, or instability in small microcontroller projects. R = 10 Ω, C = 1000 µF f_c = 1 / 2×π×10×1000×10^–6 ≈ 15.9 Hz Up