In AC analysis, capacitors and inductors oppose current change. Reactance is that opposition as an ohms-like magnitude at a given frequency f.
Formulas (ideal parts)
- Capacitive: Xc = 1 / (2πfC)
- Inductive: Xl = 2πfL
Use consistent units: farads, henries, hertz. The reactance calculator computes Xc or Xl and shows magnitude.
Practical note
Real capacitors have ESR and ESL; real inductors have DCR. At switching frequencies, use the vendor impedance curve, not ideal Xc alone.