RC Time Constant Calculator
Time constant τ and cutoff frequency from R and C.
Values
Result
τ = 1.00 s · fc = 0.159 Hz
RC time constant
The RC time constant is τ = R·C. It's the time for a capacitor to charge to ~63.2% (1 − e⁻¹) or discharge to ~36.8% of its initial voltage. After 5τ the transient is essentially complete.
The −3 dB cutoff of the RC low-pass is fc = 1 / (2πRC). Use this for debounce, timing, and simple filtering.