Capacitor Charge and Time Constant Calculator

Online calculator for calculating the Time Constant and the Charging Voltage


On this page you can calculate the charging voltage of a capacitor in an R/C circuit (low pass) at a specific point in time.

In addition to the values of the resistor and the capacitor, the applied input voltage and the time are given for the calculation.

The result shows the charging voltage at the specified time and the time constant τ (tau) of the RC circuit. The condenser is after a time of 5 τ approx. 99.33% charged. This means that at specified times that are significantly over 5 τ the input voltage is always close to the charging voltage.

Online calculator

Enter the four values in the appropriate fields.

Note the unit of measurement.



Applied voltage

Charging time

Time constant

Charging voltage

Decimal places

Formula for calculating the charging voltage

\(\displaystyle U_C=U_0 ·\left(1-e^{-\frac{t}{τ}}\right)\)

\(\displaystyle τ=R ·C\)


\(\displaystyle R\)

Resistor (Ω)

\(\displaystyle C\)

Capacitor (F)

\(\displaystyle τ\)

Time constant (sec)

\(\displaystyle U_0\)

Applied voltage (V)

\(\displaystyle U_C\)

Charging voltage at the capacitor (V)