Enter the resistance in ohms and capacitance in farads into the calculator to determine the total time to charge a capacitor.

Capacitor Charge Time Formula

The following formula can be used to calculate the charge time of a capacitor.

T = R * C * 5
  • Where T is the time (seconds)
  • R is the resistance (ohms)
  • C is the capacitance (farads)

To calculate the capacitor charge time in seconds, multiply the resistance by the capacitance, then again by 5.

Capacitor Charge Time Definition

A capacitor charge time is defined as the time it takes a capacitor to charge to 99%. This value is equal to 5 capacitor time constants.

Capacitor Charge Time Example

How to calculate capacitor charge time?

  1. First, determine the resistance.

    Measure the resistance of the capacitor.

  2. Next, determine the capacitance.

    Calculate the capacitance of the capacitor.

  3. Finally, calculate the charge time.

    Calculate the capacitor charge time using the equation above.


How long does a capacitor take to charge?

A capacitor will reach a 99% charge after 5-time constants and 63.2% after just one time constant. The time constant is calculated using the formula t = R*C. Typically either 4 or 5-time constants a capacitor is considered a full charge. (It will never reach 100% charge.

How long does a capacitor take to discharge?

Conversely, a capacitor will discharge only 36.8% after one time constant, but also reach near 99% discharge at around 5-time constants.