High-Pass Filter Calculator — RC Cutoff Frequency
Enter the resistor and capacitor values of a first-order RC high-pass filter to get the −3 dB cutoff frequency, time constant and the full frequency-response curve — all from fc = 1/(2πRC).
Ω
µF
Frequencies above this pass; below this are attenuated. At fc the signal is reduced to 70.7% (−3 dB).
- 1
Capacitance in farads
C = 1 µF ÷ 1 000 000 = 0.000001 F - 2
Time constant τ = R × C
τ = 1,000 × 0.000001 = 1 ms - 3
Cutoff frequency f_c = 1 ÷ (2π × τ)
f_c = 1 ÷ (2π × 0.001) = 159.15
How does this calculator work?
An RC high-pass filter cuts frequencies below fc = 1/(2πRC). At the cutoff the signal is at −3 dB (70.7% amplitude, 45° phase shift); below fc it rolls off at −20 dB/decade. Enter R (ohms) and C (µF) to get the cutoff frequency and time constant τ = RC.
Formula
How this is calculated
A first-order RC high-pass filter passes signals above its cutoff frequency and attenuates signals below it. The circuit places a capacitor in series with the signal path and a resistor to ground: at high frequencies the capacitor looks like a short circuit (low impedance) so most of the signal reaches the output; at low frequencies the capacitor blocks the signal. The cutoff (−3 dB) frequency is fc = 1/(2πRC), where R is in ohms and C is in farads.
At the cutoff frequency the output amplitude equals 1/√2 (about 70.7%) of the input — a drop of 3 decibels. Above fc the filter passes signals with little attenuation; below fc the output magnitude rolls off at −20 dB per decade (a factor of 10 in amplitude for every tenfold decrease in frequency). The phase shift introduced by the filter is 90° at DC, 45° at fc, and approaches 0° at very high frequencies.
The time constant τ = RC (in seconds) sets how quickly the capacitor charges and discharges; it is related to the cutoff by fc = 1/(2πτ). This calculator covers the ideal first-order RC case. Real components have parasitic inductance and capacitance, and op-amp active filters can achieve sharper roll-offs with second- or higher-order designs.
Frequently asked questions
It allows high-frequency signals to pass through while blocking or attenuating low-frequency signals below the cutoff frequency fc. Common uses include removing DC offset, audio treble boost, and separating AC from DC in sensor circuits.
Rearrange the formula: R × C = 1/(2π × fc). Pick a convenient capacitor value (e.g. 0.1 µF) then calculate R = 1/(2π × fc × C). Standard resistor values are widely available so round to the nearest E24 or E96 value.
The −3 dB point (cutoff frequency) is where the filter reduces the input signal power by half — or equivalently, reduces the amplitude to 1/√2 ≈ 70.7% of the input. It is the standard boundary between the passband and the stop-band for a first-order filter.
Also known as
TG we-Calculate Editorial Team. (2026). High-Pass Filter Calculator — RC Cutoff Frequency [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/high-pass-filter-calculator
TG we-Calculate Editorial Team. "High-Pass Filter Calculator — RC Cutoff Frequency." TG we-Calculate. 2026. https://we-calculate.com/calculator/high-pass-filter-calculator.
TG we-Calculate Editorial Team, "High-Pass Filter Calculator — RC Cutoff Frequency," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/high-pass-filter-calculator
@misc{wecalculate_high_pass_filter_calculator, title = {High-Pass Filter Calculator — RC Cutoff Frequency}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/high-pass-filter-calculator}}, year = {2026}, note = {TG we-Calculate} }
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