Electronics Calculator

Inductor Energy Calculator

Calculate the magnetic energy stored in an inductor from inductance and current using E = ½LI². You can also calculate the required inductance or current when the desired stored energy is known.

Inductor Energy

Select what you want to calculate and enter the known inductance, current and energy.

Calculation mode
A
In Energy mode this field is calculated automatically from L and I.
Quick presets
Key relationship
Inductor energy increases linearly with inductance but with the square of current: E = ½LI² .

Results

Calculated magnetic energy and related electrical quantities.

Stored Energy
—
E = ½LI²
Inductance
—
L
Current
—
I
Current Squared
—
A²
Energy
—
Joules
Magnetic Energy
—
Wh equivalent
Derived value

Inductor Energy Formula

An inductor stores energy in the magnetic field created by current flowing through its winding. The ideal stored energy depends on inductance and current.

E = ½LI²
E = energy in joules, L = inductance in henries, I = current in amperes

Calculating Required Inductance

L = 2E / I²
Used when desired energy and current are known

Calculating Required Current

I = √(2E / L)
Used when desired energy and inductance are known

Energy in Watt-Hours

EWh = EJ / 3600
1 Wh = 3600 J

How Inductor Energy Works

When current flows through an inductor, the magnetic field around its winding stores energy. If the current changes, the inductor opposes that change by generating an induced voltage.

The energy relationship is especially sensitive to current because current is squared in the formula.

Example: 1 mH at 1 A

E = ½ × 1 mH × (1 A)²

E = 0.5 × 0.001 × 1

E = 0.5 mJ

Doubling Current

If inductance remains constant and current doubles, the stored magnetic energy becomes four times larger.

For example, increasing current from 2 A to 4 A changes I² from 4 to 16. The stored energy therefore increases by a factor of four, assuming the inductor remains within its operating limits.

Energy Stored in an Inductor

The energy is stored in the magnetic field surrounding the inductor's winding. Current creates the magnetic field, while the inductance determines how much energy can be stored for a given current.

Inductor winding Magnetic field stores energy I

Applications of Inductor Energy

  • Switching power supplies and DC-DC converters.
  • Buck, boost and buck-boost converter inductors.
  • Flyback and transformer magnetic components.
  • Energy transfer in power electronics.
  • Current smoothing and ripple reduction.
  • LC filters and resonant circuits.
  • Pulse-power and magnetic energy storage.
  • Electromagnetic and actuator circuits.

Practical Design Considerations

Core Saturation

Many power inductors use magnetic cores that can approach saturation as current increases. Near saturation, the effective inductance can decrease substantially, so the simple constant-L calculation becomes less representative.

Current Rating

Real inductors have current limits determined by winding heating, core behavior, saturation and manufacturer specifications.

DC Resistance

Winding resistance causes I²R losses. The ideal formula describes stored magnetic energy but does not include copper losses.

Frequency Effects

At higher frequencies, skin effect, proximity effect, core losses and parasitic capacitance can affect real inductor behavior.

Energy Recovery

When current decreases, the stored magnetic energy is released back into the circuit or transferred to another component, depending on the circuit topology.

Inductor Energy Examples

Example 1: Small Inductor

L = 10 µH
I = 2 A

E = ½ × 10 µH × 2²

E = 20 µJ

Example 2: Power Inductor

L = 100 µH
I = 3 A

E = ½ × 100 µH × 3²

E = 0.45 mJ

Example 3: Required Inductance

E = 1 J
I = 10 A

L = 2E / I²
L = 2 / 100

L = 20 mH

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Inductor Energy Calculator FAQ

Common questions about magnetic energy, inductance and current.

The energy stored in an inductor is calculated with E = ½LI², where E is energy in joules, L is inductance in henries and I is current in amperes.
The standard inductor energy formula is E = ½LI². Because current is squared, doubling the current increases the stored energy by a factor of four.
Using E = ½LI², a 1 mH inductor carrying 1 A stores 0.0005 J, or 0.5 mJ.
Inductor energy is proportional to the square of current. If inductance remains constant and current doubles, the stored energy becomes four times larger.
At a fixed current, stored energy is directly proportional to inductance. Doubling inductance doubles the stored energy.
Yes. The ideal stored magnetic energy is completely determined by inductance and current using E = ½LI².
Energy is measured in joules (J). Small inductors commonly store energy in microjoules or millijoules, while larger power inductors and magnetic components can store substantially more.
Yes. Real inductors have current ratings and may experience core saturation, heating and increased losses at high current. The ideal formula does not account for these practical limitations.