The calculation, without hidden assumptions
Reactance is the frequency-dependent opposition of an ideal inductor or capacitor to sinusoidal AC. One parent calculator is more useful than splitting the same relationship into reciprocal formula pages: choose inductive or capacitive mode, solve for any one of the three variables, or enter both L and C to find ideal LC resonance. Engineering units are converted to SI before calculation and the substituted values stay visible.
How to use this calculator
Choose Inductive, Capacitive or LC resonance.
For a reactance mode, choose the unknown and enter the other two quantities with their units; for resonance enter L and C.
Check the SI conversion, substituted formula and optional current context before using the result in a wider circuit model.
Where people use it
- •Audio crossover and filter sanity checks
- •Mains-frequency capacitor or choke calculations
- •RF component and resonant-frequency checks
- •Teaching how XL rises and XC falls with frequency
Example: 10 mH at 1 kHz
XL = 2π × 1000 × 0.01 ≈ 62.83 Ω. Doubling frequency doubles ideal inductive reactance; for a capacitor the same frequency increase would halve XC.
What the result does not assume
- •These are ideal lumped-component formulas. Real inductors and capacitors also have resistance, parasitic capacitance/inductance, tolerance, losses, self-resonance and frequency-dependent behavior.
- •Reactance is not the same as resistance, even though both are measured in ohms. Full circuit current can require complex impedance and phase.
- •Do not use an ideal reactance result alone for safety-critical component selection, insulation, thermal design or mains compliance.
Frequently asked questions
What is inductive reactance?+
For an ideal inductor, XL = 2πfL. It rises in direct proportion to frequency and inductance.
What is capacitive reactance?+
For an ideal capacitor, XC = 1/(2πfC). It falls as frequency or capacitance increases.
What happens at LC resonance?+
In the ideal relationship XL equals XC at f0 = 1/(2π√(LC)). The surrounding circuit topology and losses determine the real impedance at resonance.
Can I solve backward for L, C or frequency?+
Yes. In inductive and capacitive modes choose the unknown; MAXScanner rearranges the same physical relationship instead of sending you to a duplicate page.
Semantic next steps
Continue the calculation
These links move to a different input, formula or project stage rather than a keyword variation of this page.
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