Capacitor Inrush Current Calculator

This handy tool calculates the inrush current of a capacitor or capacitive load.


To find this value enter:

  • Capacitor value (F)
  • Change in Voltage (dV)
  • Time duration (dt)




I = C * dV/dt


  • C is the capacitor value
  • dV/dt is the rate of change of the input voltage

Example Calculation

For a capacitance value of 10 µF if there’s a change in voltage of 1 Volt over a 1 µs time interval, the inrush current is 10 Amps.

What is Inrush current?

Inrush current, also known as surge current, is the initial surge of current into an electrical device when it is first turned on. This current can be significantly higher than the steady-state operating current and can potentially cause damage or operational issues if not properly managed.

The maximum inrush current can depend on several factors, including the type of device, its power rating, the characteristics of its power supply, and the specific components involved (like capacitors and inductors).

In this post we have calculated the inrush current for a capacitive load.


Often, the most accurate inrush current values come from manufacturer datasheets or empirical testing. Manufacturers may provide specific inrush current ratings for devices, especially for complex equipment like power converters, motors, and transformers.

As well, for complex circuits or when precise calculations are needed, simulation software (e.g., SPICE models) can be used to simulate the inrush current under various conditions, taking into account the non-linear and dynamic aspects of the circuit.

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