Reference Designer Calculators

RC Time Constant Calculator

If a voltage is applied to a capacitor of Value C through a resistance of value R, the voltage across the capacitor rises slowly. The time constant is defined as the time it will take to charge to 63.21% of the final voltage value.

Following is the formula for time constant.

t = R * C

Enter two of the required values and Hit the third button to calculate the required value. You may also choose the suitable units.

  (Resistance) : None Kilo Ohm Mega Ohm
  (Capacitance) uF nF pF
  (Time Constant) seconds milli seconds micro seconds

We srongly suggest that you look at the following video in its completeness to get a complete understanding of the charging of a capacitor. In the end of the video it has a nice experiment that you can reproduce at home.