RC Low-Pass Filter Cutoff & Attenuation
Cutoff frequency, time constant and attenuation at a chosen frequency for an RC low-pass filter.
Worked example
Input: Resistance R 1000 Ω, Capacitance C 100 nF, Frequency of interest 10 kHz
Result: Cutoff frequency f_c 1591.55 Hz, Time constant τ 100 µs, Attenuation at that frequency 16.0722 dB
Result: Cutoff frequency f_c 1591.55 Hz, Time constant τ 100 µs, Attenuation at that frequency 16.0722 dB
Formula
f_c = 1 / (2π·R·C)
Attenuation = 10·log₁₀(1 + (f/f_c)²)
How it works
At the cutoff f_c = 1/(2πRC) the signal is 3 dB down, and as a first-order filter attenuation grows by 20 dB per decade above it. Use it for RC filtering on signal lines, switch debounce and anti-alias front ends.
Practical tipAn RC on a signal line also slows its rise time. Set the cutoff well above the bandwidth the signal needs but below the frequencies that cause emission problems; use it together with the rise-time/bandwidth calculator.
Related calculators
Related standards
Related guides
Results and summaries are for reference. For certification and test reports use the latest official standard text and calibrated instrument data. Last updated: 2026-10-10