RC Time Constant

Find the time constant τ = R × C for resistor‑capacitor circuits.

About RC Time Constant

The time constant τ characterizes the rate of charging/discharging of an RC circuit. After one τ, a charging capacitor reaches about 63.2% of its final voltage; after 5τ it is above 99%.

How to Use

  1. Enter resistance (Ω) and capacitance (F)
  2. Click Calculate to get τ in seconds
  3. Use multiples of τ (e.g., 5τ) to approximate settling time