Inductor Energy Calculator — E = ½LI²
Find the energy stored in an inductor's magnetic field. When current flows through an inductor, it builds a magnetic field that holds energy — proportional to the inductance and the square of the current.
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Energy stored in the magnetic field: E = ½ × L × I²
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Square the current
I² = 2 × 2 = 4 - 2
Multiply by inductance
L × I² = 0.5 × 4 = 2 - 3
Energy stored
E = ½ × 0.5 × 4 = 1Energy stored in the magnetic field: E = ½ × L × I².
How does this calculator work?
An inductor stores E = ½ × L × I² joules in its magnetic field, where L is inductance in henries and I is current in amperes. Energy scales with the square of current — doubling current quadruples stored energy. Enter L and I to get energy in joules instantly.
Formula
How this is calculated
An inductor (coil) stores energy in the magnetic field it creates while current flows. The stored energy is E = ½ × L × I², where L is the inductance in henries and I is the current in amperes. This is the magnetic analogue of capacitor energy storage (E = ½CV²).
The quadratic dependence on current is the key practical fact: doubling the current quadruples the stored energy. This energy is non-dissipative — it is returned to the circuit when the current changes or stops. If the circuit is broken suddenly, the collapsing field drives current to continue flowing and generates a large inductive voltage spike (V = L × dI/dt). This is why flyback (freewheeling) diodes are fitted in switching power supplies and motor drivers to provide a safe discharge path.
The formula assumes the inductor operates below its saturation current rating. Real inductors have a maximum current beyond which the core saturates, inductance drops sharply, and the formula overestimates stored energy. Always check the saturation current specification when designing power circuits.
Frequently asked questions
In the magnetic field that permeates the space around and inside the coil, particularly in the core material. The energy density is proportional to B² (the square of the magnetic flux density), so a stronger field stores more energy per unit volume.
The collapsing magnetic field drives current to continue flowing and can generate a large inductive voltage spike (V = L × dI/dt). In switching power supplies and motor drivers, flyback diodes provide a safe discharge path to prevent component damage from these transients.
Both store energy quadratically: inductors store E = ½LI² magnetically, capacitors store E = ½CV² electrically. In an LC resonant circuit they continuously exchange this energy at resonant frequency f = 1 / (2π√LC), forming the basis of oscillators and band-pass filters.
Also known as
TG we-Calculate Editorial Team. (2026). Inductor Energy Calculator — E = ½LI² [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/inductor-energy-calculator
TG we-Calculate Editorial Team. "Inductor Energy Calculator — E = ½LI²." TG we-Calculate. 2026. https://we-calculate.com/calculator/inductor-energy-calculator.
TG we-Calculate Editorial Team, "Inductor Energy Calculator — E = ½LI²," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/inductor-energy-calculator
@misc{wecalculate_inductor_energy_calculator, title = {Inductor Energy Calculator — E = ½LI²}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/inductor-energy-calculator}}, year = {2026}, note = {TG we-Calculate} }
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