Inductor Calculator
Reactance, energy and the L/R time constant.
Reactance, energy and the L/R time constant.
Total inductance
2 mH
Series — inductances add · reactance 12.566 Ω at 1,000 Hz
Inductors combine the same way as resistors — series adds, parallel divides — which makes them the easy half of this. The useful figure is the reactance: 2πfL, which rises in proportion to frequency. That rise is why an inductor passes DC almost freely and chokes high frequencies, and it is the whole basis of filters, chokes and transformers. Double the frequency and you double the opposition. The L/R time constant sets how quickly current builds when voltage is applied. After one time constant the current has reached 63% of its final value, and it is essentially there after five — the same shape as an RC circuit, with the roles of voltage and current swapped.
How the Inductor Calculator works
Total inductance in series or parallel, with reactance at a chosen frequency, the energy stored in the magnetic field, and the L/R time constant. Reactance rises in proportion to frequency, which is the whole reason inductors exist.
Also known as: inductive reactance at frequency · combine inductors · energy stored in an inductor · l over r time constant
Where to go next
The Inductor question rarely arrives on its own. These are the ones that usually come with it:
- LC Resonance Calculator — Where the reactances cancel, and how sharply.
- Impedance Calculator — Magnitude and phase — they do not simply add.
- Resistor Series & Parallel Calculator — Parallel is always below the smallest. That is the check.
- Speed Distance Time Calculator — Any one of the three from the other two, in four units.
Frequently asked questions
How do inductors combine?
The same way as resistors: series adds, parallel takes the reciprocal sum. That assumes no magnetic coupling between them — coupled inductors behave differently and become a transformer.
What is inductive reactance?
The opposition an inductor presents to alternating current, equal to 2πfL. It rises in proportion to frequency, so an inductor passes DC almost freely and blocks high frequencies.
How much energy does an inductor store?
Half L I squared, in the magnetic field. That stored energy is why breaking an inductive circuit produces a voltage spike — the field collapses and the energy has to go somewhere.
What is the L/R time constant?
How quickly current builds when voltage is applied. After one time constant the current reaches 63% of its final value and it is essentially there after five — the same shape as an RC circuit with voltage and current swapped.
Why do inductive loads need flyback diodes?
Because interrupting the current forces the collapsing magnetic field to dump its energy, and with nowhere to go it appears as a large reverse voltage spike that destroys switching transistors. A diode gives the current a path.
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Related calculators
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Where the reactances cancel, and how sharply.
OpenImpedance Calculator
Magnitude and phase — they do not simply add.
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OpenSpeed Distance Time Calculator
Any one of the three from the other two, in four units.
Open