RC Circuit Calculator
Analyse a series RC circuit for impedance, phase angle and filter response.
About RC Circuit Calculator
Taking the output across the capacitor gives a low-pass response; across the resistor gives high-pass. At the cutoff frequency the reactance equals the resistance and the output is 3 dB down. A single RC stage rolls off at only 6 dB per octave, which is why steeper filtering needs multiple stages or active designs.
Formula
RC Circuit
Z = √(R² + X_C²); f_c = 1 ÷ (2πRC)
- f_c
- Cutoff frequency where output falls to 70.7% of input
- phase shift
- Approaches −90° well above cutoff
Worked example
With the default values below, RC Circuit Calculator returns Circuit Impedance of 1,879.6355. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Resistanceminimum 0.01 ohm
- 1,000 ohm
- Capacitanceminimum 0 F
- 0 F
- Signal frequencyminimum 0.01 Hz
- 1,000 Hz
- Input voltageminimum 0 V
- 5 V
Results
- Circuit Impedance
- 1,879.6355 ohm
- Cutoff Frequency
- 1,591.549 Hz
- Phase Shift
- -57.858 degrees
- Output Across the Capacitor
- 4.23367 V
- Circuit Current
- 0.002660 A
Step by step
- 1Values used
- 2RC Circuit
- 3Circuit Impedance= 1,879.6355 ohm
- 4Cutoff Frequency= 1,591.549 Hz
- 5Phase Shift= -57.858 degrees
- 6Output Across the Capacitor= 4.23367 V
- 7Circuit Current= 0.002660 A
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 6 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 RC Circuit calculated?
Z = √(R² + X_C²); f_c = 1 ÷ (2πRC) Taking the output across the capacitor gives a low-pass response; across the resistor gives high-pass. At the cutoff frequency the reactance equals the resistance and the output is 3 dB down.
Why does RC Circuit matter?
A single RC stage rolls off at only 6 dB per octave, which is why steeper filtering needs multiple stages or active designs.
What values do I need to enter?
This calculator takes 4 inputs: Resistance, Capacitance, Signal frequency, Input voltage. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.