passive components

RC Time Constant

The RC time constant τ = R × C determines how quickly a capacitor charges or discharges through a resistor. One τ reaches ~63.2 % of the final voltage. Five τ (99.3 %) is the practical fully-charged threshold. The cutoff frequency (−3 dB) of the RC low-pass filter is f = 1 / (2π·τ).

Inputs

Resistance (R)(Ω)

Capacitance (C)(pF)

Enter value in picofarads (100 nF = 100,000 pF)

Results

Time Constant (τ)100.00µs

Cutoff Frequency (−3 dB)1.5915kHz

Charge Time (5τ, 99.3 %)500.00µsPractical fully-charged threshold