RC Time Constant Calculator

Calculation of the time constant of the RC circuit

The time constant of a serial RC circuit is equal to the product of resistance and capacitance. If two of the three values — resistance, capacitance, or RC time constant-are present, this tool will calculate the missing third variable.

In an electrical circuit consisting of a capacitance and resistance connected in series, the voltage source $V_S$ is initially isolated from a resistor $R$ and a capacitor $C$ connected in series by an open switch. When the switch is closed, current will flow in the circuit, the capacitor will start charging, and the voltage at its terminals will increase exponentially, and the current flowing in the circuit will decrease exponentially.

Calculation formula

The charging and discharging rate of successive RC circuits is characterized by the RC time constant, which is denoted by – $\tau$, calculated by the following equation:

Where:

$\tau$ – time constant in seconds

$R$ – resistance in ohms

$C$ – capacitance in farads

Application

RC circuits are widely used as timing elements.