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Electrical

RC Filter Cutoff Frequency Calculator

Find the −3 dB cutoff of a first-order RC filter.

Ideal component relationshipsUnits and assumptions explained below
Circuit workbench
Circuit workbench

Keep RMS, peak and DC values distinct.

See the method

Enter circuit values

Runs on your device

Your circuit result

Your result

Let’s calculate.

Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter resistance, capacitance.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

Input reference and sample values

Use the units and choices shown for each field. Sample values are provided for practice, not as recommendations.

InputFormat and unitsSample
ResistanceNumeric value. Unit: Ω. Must be greater than zero.100
CapacitanceNumeric value. Unit: F. Must be greater than zero.0.0001

Result for these sample inputs

15.9154943 Hz

Select Try the example in the form to load these values and calculate them again. This replaces the current form inputs. Compare the result with the method and worked explanation below.

The method, explained

Cutoff frequency = 1/(2πRC).

A WORKED EXAMPLE

Using resistance = 100 Ω, capacitance = 0.0001 F, the result is 15.9154943 Hz. Change these example inputs to match your task; use the method above to check each step.

What to keep in mind

Ideal-component calculation for study and estimation. It does not select safe wiring, protective devices or component ratings for an installation.

Methodology maintained by ClarityKit. How these tools are built and checked.