RC High-Pass Filter Calculator
Enter any two of R, C and cutoff frequency to solve the third — first-order RC high-pass.
What it does: Compute the cutoff frequency of a first-order RC high-pass filter, or solve back for the R/C you need.
When to use it: For DC-blocking coupling, removing low-frequency drift / mains hum, or AC coupling.
MEANS Signals above — mostly pass; those below it (including DC) are attenuated.
No history yet. Each calculation is automatically saved to this device.
How to use the high-pass filter calculator
Enter two values to solve for one.
- 01
Enter two of the values
Fill in any two of R, C and the cutoff frequency fc, and leave the third blank. Supports
10k,100n,1kHz. - 02
Click Calculate
The tool solves for the value you left blank. In a high-pass filter the capacitor is in the signal path and the output is taken across the resistor.
- 03
Read fc
fc is the −3 dB corner: frequencies above it pass, frequencies below it (including DC) are attenuated.
Common questions, answered in 3 minutes
Do high-pass and low-pass use the same formula?
The cutoff frequency formula for a first-order RC is exactly the same, fc = 1/(2πRC); the only difference is where the output is taken — across the resistor = high-pass, across the capacitor = low-pass.
Can a high-pass filter block DC?
Yes. A series capacitor is an open circuit to DC, so a high-pass filter naturally blocks DC (this is how coupling capacitors work) and passes only the AC component.
What point is fc?
The frequency where the gain rises to −3 dB (about 0.707×), which engineers treat as the lower edge of the passband.
How do I get a steeper roll-off?
A first-order RC gives +20 dB/decade. For a steeper slope you need multiple cascaded stages or an active filter (Sallen-Key, etc.).
Standards and sources referenced by this tool
| Item | Value / Formula | Source |
|---|---|---|
| Cutoff frequency | fc = 1/(2π·R·C) | First-order RC filter |
First-order RC formula, no external API.