Inductor Energy Calculator
This inductor energy calculator finds the energy stored in an inductor from its inductance and the current through it, using E = ½ L I². Enter both and the inductor energy calculator returns the stored energy in joules and millijoules. It applies the energy stored in inductor formula directly.
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The Inductor Energy Calculator is part of our Electronics collection. Browse more electronics to size, convert, and check your work alongside this tool.
What the inductor energy calculator shows
An inductor stores energy in the magnetic field created by the current through it. This inductor energy calculator finds how much, from the inductance and the current, using E = ½ L I². The energy rises with the square of the current, so doubling the current stores four times the energy. As an inductor energy storage calculator it gives the result in joules and millijoules.
The energy stored in inductor formula
The energy stored in inductor formula is:
L is the inductance in henries and I is the current in amps, giving energy in joules. The current is squared, so it dominates: the energy is set far more by how much current flows than by the inductance. This is the magnetic mirror of a capacitor storing energy in an electric field.
Inductor energy formula example
A 10 mH inductor carrying 2 A. The inductor energy formula gives:
So the inductor stores 20 millijoules in its magnetic field. Change the current and the inductor energy calculator updates the energy at once.
How to use the inductor energy calculator
Enter the inductance in millihenries and the current in amps, then the inductor energy calculator returns the stored energy in joules and millijoules. Read the inductance from the component and the current from the circuit. Because the current is squared, the working current matters far more than the inductance for the stored energy.
Reading the inductor energy calculator result
The stored energy is what the inductor releases when the current tries to stop, which is why switching an inductive load produces a voltage spike as that energy has to go somewhere. That is the reason relays and motors need a flyback diode to absorb it safely. Because the energy grows with the square of the current, a high current inductor stores a lot, so size snubbers and diodes for the working current, not just the inductance.
When to use the inductor energy storage calculator
- Sizing a flyback diode with the inductor energy storage calculator
- Finding the energy in a buck or boost converter inductor
- Working an energy stored in inductor formula problem
- Comparing inductor and capacitor energy storage
Common inductor energy calculator mistakes
- Ignoring the square. Energy grows with the current squared, so small current changes move it a lot.
- Wrong inductance unit. A millihenry is a thousandth of a henry; convert before the formula.
- Forgetting the spike. The stored energy must be released, so protect inductive switches.
Tips for inductor energy
- Use the peak working current, since it is squared.
- Add a flyback diode to absorb the stored energy on switch off.
- Check the core will not saturate at the peak energy.
The energy stored in inductor formula explained
The energy stored in inductor formula, E = ½ L I², comes from building the current up from zero: as the current rises, the inductor opposes the change and the source does work against that opposition, and the work stored is half the inductance times the final current squared. The square on the current is the key feature: an inductor at 4 A holds four times the energy it holds at 2 A, so high current chokes and motor windings store surprisingly large amounts. That stored energy is real and must be released when the circuit opens, which is the physical reason an inductor resists a sudden change in current and produces a back voltage when you try to force one.
Inductor energy storage calculator uses
An inductor energy storage calculator is most useful in switching power supplies and protection design. In a buck or boost converter the inductor charges and discharges every cycle, and its peak energy sets the core size and the current rating, so knowing E = ½ L I² helps pick a part that will not saturate. In relays, solenoids, and motors, the same stored energy is what a flyback diode must absorb when the coil switches off, or the voltage spike will damage the switch. Because the inductor stores in a magnetic field while a capacitor stores in an electric field, the two trade energy back and forth in a resonant circuit at its resonant frequency.
Inductor energy formula values
Stored energy for several inductance and current pairs, from the inductor energy formula:
| Inductance | Current | Energy |
|---|---|---|
| 10 mH | 2 A | 20 mJ |
| 10 mH | 4 A | 80 mJ |
| 100 mH | 2 A | 200 mJ |
| 1 mH | 10 A | 50 mJ |
Inductor Energy Calculator FAQ
What is the energy stored in inductor formula?
The formula is E = half L I squared, inductance times current squared, halved. The inductor energy calculator applies it and returns joules and millijoules.
Why does current matter so much?
Because it is squared. Doubling the current stores four times the energy, so the working current sets the stored energy far more than the inductance does.
Where does the energy go when the current stops?
It has to be released, producing a voltage spike, which is why inductive loads need a flyback diode or snubber to absorb it safely.
How does it compare to a capacitor?
An inductor stores energy in a magnetic field as half L I squared; a capacitor stores it in an electric field as half C V squared. They are mirror images.