Case 1
- Resistance R (Ω)
- 1000Ω
- Capacitance C (µF)
- 1µF
159.1549Hz
Open with these valuesRC High-Pass Filter Calculator
159.1549Hz
Result: 159.1549 HzA high-pass filter passes everything above its cutoff and blocks what is below, DC included. The cutoff is the −3 dB point, where the output has fallen to about 70.7 % of the input. Same formula as the low-pass filter, opposite pass band. Enter ohms and microfarads: 100 nF is 0.1 µF.
Worked examples
Case 2
- Resistance R (Ω)
- 4700Ω
- Capacitance C (µF)
- 0.01µF
3,386.2754Hz
Open with these valuesCase 3
- Resistance R (Ω)
- 470Ω
- Capacitance C (µF)
- 0.22µF
1,539.2161Hz
Open with these valuesHow it's calculated
f_c = 1 / (2π × R × C)
- StepEnter the resistor value in ohms — 4.7 kΩ is 4700.
- StepEnter the capacitor value in microfarads — 10 nF is 0.01.
- ResultRead the cutoff; everything above it passes, everything below rolls off.
Reference table
| R (Ω), C (µF) | Time constant τ | Cutoff (Hz) |
|---|---|---|
| 100000, 10 | 1 s | 0.1592 |
| 1000, 1 | 1 ms | 159.1549 |
| 10000, 0.1 | 1 ms | 159.1549 |
| 2200, 0.047 | 103.4 µs | 1539.2161 |
| 470, 0.22 | 103.4 µs | 1539.2161 |
| 4700, 0.01 | 47 µs | 3386.2754 |
Questions
How do I calculate the cutoff frequency of an RC high-pass filter?
Use f_c = 1 / (2π × R × C), with R in ohms and C in farads. For R = 1 kΩ and C = 1 µF that is about 159.15 Hz. The same parts give the same cutoff in a low-pass filter — only the pass band differs.
What does a high-pass filter do?
It passes frequencies above the cutoff and attenuates those below it, blocking DC entirely. It is used to remove a DC offset, couple audio stages, strip low-frequency hum and pass the fast edges of a signal. Below the cutoff the response rolls off at 20 dB per decade.
How is a high-pass filter different from a low-pass filter?
Both use f_c = 1 / (2π × R × C), so the same R and C give the same cutoff frequency. The difference is the pass band: a high-pass passes above f_c, a low-pass below it. In the circuit the capacitor and the resistor swap positions.
What does the cutoff frequency mean?
The cutoff is the −3 dB point: exactly at f_c the output amplitude is about 70.7 % of the input. Above it the signal passes nearly intact, below it the filter rolls off at 20 dB per decade. It is the boundary between the band you keep and the low frequencies you want gone.
Do I enter the capacitance in farads or microfarads?
In microfarads (µF). A 100 nF capacitor is 0.1 µF, a 10 nF capacitor is 0.01 µF and a 1 nF capacitor is 0.001 µF. Entering raw farads would give a cutoff a million times too high, and the wrong number still looks believable.
Sources and last check
Information, not professional advice.