Inductor Energy Calculator
Find the energy stored in an inductor.
Results update as you type.
How it works
An inductor stores energy in the magnetic field created by current flowing through it, and this calculator computes that stored energy. You enter the inductance and the current, and it returns the energy in joules and millijoules. The formula is one-half times the inductance times the current squared, analogous to the energy stored in a capacitor or the kinetic energy of a moving mass. The energy depends on the current squared, so doubling the current quadruples the stored energy, while it depends linearly on inductance. This stored energy is central to how inductors behave in circuits: because energy cannot change instantly, an inductor resists sudden changes in current, which is why it smooths current, filters signals, and stores energy in switching power supplies. When the current through an inductor is interrupted, the stored magnetic energy must go somewhere, which is why breaking an inductive circuit can produce a voltage spike, a fact important in designing switches, relays, and protection circuits. Understanding inductor energy is essential in power electronics, where inductors in buck and boost converters store and release energy each switching cycle to transform voltages efficiently, and in energy storage, filtering, and tuned circuits. Inductance is in henries and current in amperes to give energy in joules. Enter the inductance and current to find the stored energy.
E = ½ × L × I²
An inductor stores energy in its magnetic field when current flows through it. The energy equals one-half times the inductance times the current squared. Because current is squared, doubling the current quadruples the stored energy, while energy grows linearly with inductance.
Source:Electrical engineering
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter inductance and current.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Stored energy updates instantly as you type — no button to press.
Frequently asked questions
How much energy does an inductor store?
The energy stored in an inductor is one-half times its inductance times the current squared. For a 0.5 henry inductor carrying 2 amperes, that is one-half times 0.5 times 4, or 1 joule. The energy is held in the magnetic field the current creates, and the calculator computes it from your inductance and current.
Why is current squared in the formula?
The energy depends on the current squared because the magnetic field strength is proportional to current, and the stored energy grows with the square of the field. This means current has a strong effect: doubling the current quadruples the stored energy, while changing the inductance only scales energy linearly.
Why does an inductor resist changes in current?
Because an inductor stores energy in its magnetic field, and that energy cannot change instantly, the inductor opposes sudden changes in the current flowing through it. This property makes inductors useful for smoothing current, filtering, and energy storage, and it is described by the relationship between voltage, inductance, and the rate of change of current.
What causes voltage spikes when switching inductors?
When the current through an inductor is suddenly interrupted, the stored magnetic energy must be released, and a rapidly collapsing field induces a large voltage. This spike can damage switches or components, which is why circuits with relays, motors, or solenoids include protection like flyback diodes to safely dissipate the inductor's stored energy.
Where is inductor energy storage important?
It is central to switching power supplies, where inductors in buck and boost converters store and release energy each cycle to change voltage efficiently, and to filters, tuned circuits, and energy storage applications. Understanding how much energy an inductor holds helps engineers design these circuits and manage the energy safely during switching.