What is the formula for energy stored in an inductor?

E = ½ × L × I², where L is the inductance in henries and I is the current in amperes. The result is in joules.

Why does doubling the current quadruple the stored energy?

Current is squared in the formula. Doubling I makes I² four times larger, so the stored energy increases by a factor of four. This makes current the dominant variable in inductor energy storage.

What units are accepted for inductance?

This calculator accepts henries (H), millihenries (mH), microhenries (µH), and nanohenries (nH). Select the correct unit before entering the value.

Where is the energy physically stored in an inductor?

The energy is stored in the magnetic field that builds up around the inductor coil when current flows through it. When the current drops, this field collapses and the energy is released back into the circuit.

Is there an equivalent formula using magnetic flux?

Yes. Since the magnetic flux linkage Ψ = L × I, you can write E = Ψ² / (2L) or E = ½ × Ψ × I. All forms are mathematically equivalent to E = ½LI².

How does inductor energy storage compare to a capacitor?

A capacitor stores energy in an electric field (E = ½CV²) while an inductor stores it in a magnetic field (E = ½LI²). The formulas are analogous, with L ↔ C and I ↔ V.

Energy Stored in an Inductor

Enter inductance and current to calculate the magnetic energy stored in an inductor using E = ½LI².

Inputs

Inductance (L)

Current (I)

Formula

E = ½ × L × I²

E in joules, L in henries, I in amperes

Result

Enter values and click Calculate

Copied!

Summary

This calculator uses E = ½ × L × I² to find the magnetic energy an inductor holds at a given current. Enter inductance in any common unit (H down to nH) and current in amperes or milliamperes, and the tool returns the result in joules with millijoule and microjoule equivalents. The working section shows the full substituted calculation so you can verify each step.

How it works

Enter the inductance value and select its unit.
Enter the current flowing through the inductor.
The calculator converts both values to SI base units (H and A).
It applies E = ½ × L × I² and returns the result in joules.
Millijoule and microjoule equivalents are displayed for convenience.

Use cases

Determine the energy released when an inductor is switched off in a power supply.
Size snubber circuits by knowing how much energy the inductor will dump.
Verify textbook physics problems involving magnetic field energy storage.
Compare energy storage between inductor designs at a given operating current.
Calculate flyback energy in DC-DC converter inductor design.
Understand how inductance and current trade off for a fixed energy target.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu