Last updated September 28, 2026 · Report an error
An inductor stores energy in its magnetic field, proportional to its inductance and the square of the current flowing through it. This calculator solves for whichever value — inductance, current, or stored energy — is missing.
How it works
Enter any 2 of the 3 values (inductance in millihenries, current, or energy in millijoules) and leave the one you want to solve for blank. The calculator applies E = ½LI².
- Enter inductance (mH) — leave blank to solve for this.
- Enter current (A) — leave blank to solve for this.
- Enter energy (mJ) — leave blank to solve for this.
- Click Calculate to see your results.
Examples
A charged inductor
A 10 mH inductor carrying 2A of current stores 20 millijoules of energy.
Who should use it
- Electronics coursework on inductor behavior.
- Estimating stored energy for inductor-based circuit design (e.g. switching power supplies).
Industry applications
- Electronics and circuit design
- Power electronics design
Advantages
- Solves for any of the three variables, not just forward energy calculation.
- Simple, exact formula for ideal inductor behavior.
Limitations
- Assumes an ideal inductor — real inductors have some resistance and core losses not captured by this idealized formula.
Common mistakes to avoid
- Assuming energy scales linearly with current — it scales with the square of current, so doubling current quadruples stored energy.
- Confusing inductor energy storage with a capacitor's — they're analogous formulas but store energy in different types of fields.
Best practices
- Remember that doubling current through an inductor quadruples its stored energy, not just doubles it.
- Check a real inductor's current rating before relying on a calculated current value for a design.
Tips
- Pair this with the LC Resonant Frequency Calculator when designing a circuit that combines an inductor and capacitor together.
Frequently asked questions
Yes, with no signup and no limit on how many calculations you run.
Just like a capacitor's voltage-squared energy relationship, an inductor's stored energy builds as current ramps up, and integrating that relationship over time produces the squared-current term, not a simple direct proportion.
They're structurally analogous — a capacitor stores energy in an electric field via E = ½CV², an inductor stores it in a magnetic field via E = ½LI² — capacitance/voltage swap roles with inductance/current.
Inductance in millihenries (mH), current in amps, and energy in millijoules (mJ) — practical scales for real inductors — with the calculator converting to base SI units internally.