Formula Used
The energy stored in an ideal inductor’s magnetic field is:
To rearrange, the calculator also uses L = 2E / I² and I = √(2E / L).
How to Use This Calculator
- Select what you want to solve for: energy, inductance, or current.
- Enter the known values and choose units for each input.
- Click Calculate to view results above the form.
- Use Download CSV or Download PDF to export results.
- Compare with the example table to validate typical ranges.
Example Data Table
| Inductance (L) | Current (I) | Stored Energy (E) | Common Context |
|---|---|---|---|
| 10 mH | 2 A | 0.02 J | Small power choke |
| 100 µH | 5 A | 0.00125 J | DC-DC converter inductor |
| 1 H | 0.5 A | 0.125 J | Laboratory coil |
| 2.2 mH | 0.3 A | 0.000099 J | Signal filtering |
| 47 mH | 1.2 A | 0.03384 J | Inductive load smoothing |
Values are illustrative. Real inductors can saturate, reducing effective inductance at high current.
Inductor Energy Storage Guide
1) Understanding stored magnetic energy
An inductor stores energy in a magnetic field when current flows. This stored energy can be returned to the circuit when current decreases, which is why inductors are central to filters, converters, and pulse circuits. The energy is not “used up”; it is exchanged with the rest of the circuit.
2) The relationship used in calculations
Engineers typically use E = ½·L·I², where E is joules, L is henry, and I is ampere. Current dominates because it is squared: doubling current makes energy four times larger. Example: 10 µH at 5 A stores 0.125 mJ.
3) Typical component ranges
Inductance values vary by application: RF parts may be 10 nH–10 µH, power inductors commonly 1 µH–1 mH, and low‑frequency coils can reach tens of mH or more. Higher inductance usually increases winding resistance and size, so the “best” value depends on ripple and transient targets.
4) Current limits and core saturation
Real inductors are limited by copper heating and core saturation. Near saturation, effective inductance drops, ripple rises, and losses increase. Keep margin between operating current and the saturation rating, especially for load steps and startup surges.
5) Why ripple current matters
In switching supplies, energy rises and falls every cycle. If current swings from 2 A to 4 A in a 22 µH inductor, energy varies from 44 µJ to 176 µJ. That spread helps estimate transient stress on switches, diodes, and the output capacitor.
6) Linking voltage pulses to current change
For pulses, V = L·(dI/dt) connects applied voltage to the current ramp. A 12 V pulse across 100 µH gives an ideal slope of 120 kA/s, so current increases about 1.2 A over 10 µs. Combine that current with ½·L·I² to estimate pulse energy.
7) Unit conversions you will see
Datasheets often use µH (10⁻⁶ H) and mH (10⁻³ H). Energy may be shown in µJ, mJ, or J. Quick check: with L fixed, energy scales with I², so high-current designs accumulate energy rapidly. Always note tolerances, since L can vary with temperature and bias current.
8) Verification before hardware testing
Validate saturation current, winding resistance (I²R loss), and temperature rise. For measurements, fast ripple may require a shunt and oscilloscope rather than a clamp meter. Use this calculator to compare scenarios, capture assumptions, and document results consistently for reports.
Frequently Asked Questions
1) What does an inductor store energy in?
It stores energy in a magnetic field created by current through its windings. The stored energy can be released back to the circuit when current decreases.
2) Why does energy depend on current squared?
Magnetic field strength is proportional to current, and energy relates to field strength. This results in the quadratic term, so doubling current increases energy fourfold.
3) What happens when an inductor saturates?
Core saturation reduces effective inductance, causing higher ripple current and extra losses. Calculations assuming constant L may underpredict stress near saturation.
4) Can I use this for AC currents?
You can estimate energy using instantaneous or peak current with the inductance value, but real AC behavior also involves resistance, frequency effects, and waveform shape.
5) How accurate are datasheet inductance values?
Inductance varies with current, temperature, and frequency. Datasheets typically specify test conditions, so measure L under your operating conditions for best accuracy.
6) What is a quick example calculation?
If L = 1 mH and I = 2 A, then E = 0.5 × 0.001 × 4 = 0.002 J, which equals 2 mJ.
7) Is higher inductance always better for energy storage?
Not always. Higher inductance can mean higher resistance, larger size, and lower saturation current. Choose L to meet ripple, transient, and efficiency requirements.