Calculators
Inductor Energy Calculator
Calculate energy stored in an inductor from inductance and current.
Calculate ideal magnetic energy stored in an inductor from inductance and current using E = ½LI².
Stored magnetic energy
20 mJ
Ideal relationship: E = ½LI². Reversing current direction does not change the stored-energy magnitude because current is squared.
About This Tool
An inductor stores energy in the magnetic field created while current flows through it. This calculator finds that ideal stored energy from inductance and current using E = ½LI². It is useful for physics and electronics study, checking circuit calculations, and understanding how strongly stored magnetic energy changes with current. The calculation runs locally in your browser.
How To Use It
- Enter the inductance and select henries, millihenries, microhenries, or nanohenries.
- Enter the current through the inductor and choose amperes, milliamperes, or microamperes.
- Choose the desired energy output unit and read the stored magnetic energy.
- Treat the result as an ideal calculation; practical inductors have current ratings, resistance, core losses, saturation, and transient behavior.
Examples
10 mH at 2 A
For L = 10 mH and I = 2 A, E = ½ × 0.01 × 2² = 0.02 J, or 20 mJ.
0.632 mH at 30 A
An inductance of 0.632 mH carrying 30 A stores about 0.284 J in the ideal model.
Current has a squared effect
At fixed inductance, doubling current makes stored energy four times larger because current is squared in E = ½LI².
Useful Notes
Inductor energy formula
The ideal stored-energy equation is E = ½LI², where E is energy in joules, L is inductance in henries, and I is current in amperes.
Energy is stored in the magnetic field
As current builds through an inductor, its magnetic field stores energy. When current decreases, that field can return energy to the circuit. This energy-storage behavior is closely related to an inductor's opposition to rapid changes in current.
Why current is squared
Stored energy is proportional to I². If inductance remains constant, doubling current quadruples energy, while halving current reduces energy to one quarter.
Current direction and stored energy
Changing current direction reverses the magnetic-field direction but does not make stored energy negative. The ideal energy magnitude is unchanged because current is squared.
Ideal model and practical limits
The formula assumes the stated inductance remains valid at the chosen current. Real inductors can have winding resistance, core losses, heating, current limits, and magnetic saturation that changes effective inductance. Interrupting current can also produce large induced voltages, so this result is not a component or safety rating.
FAQ
What is the formula for energy stored in an inductor?
For an ideal inductor, E = ½LI². Use inductance in henries and current in amperes to obtain energy in joules.
What happens to inductor energy if current doubles?
At constant inductance, stored energy becomes four times larger because energy is proportional to the square of current.
Does negative current mean negative stored energy?
No. Current direction affects magnetic-field direction, but I² makes the ideal stored-energy magnitude non-negative.
Is the calculated energy a safe operating limit?
No. Real component limits depend on saturation current, winding resistance, temperature, core losses, transient voltage, insulation, manufacturer ratings, and the surrounding circuit.
Related Tools
Series & Parallel Inductor Calculator
Combine inductors in series or parallel and calculate reactance.
LC Resonance Calculator
Calculate LC resonant frequency and reactance from inductance and capacitance.
Capacitor Energy Calculator
Calculate energy stored in a capacitor from capacitance and voltage.
Energy Converter
Convert J, kJ, MJ, Wh, kWh, cal, kcal, and BTU.