Inductor Calculator

An ideal inductor stores energy in its magnetic field and opposes changes in current. Its impedance XL = 2πfL increases linearly with frequency — at DC it acts as a short circuit, at high frequencies it blocks current. This frequency-dependent behavior is what makes inductors essential in filters, oscillators, and power supplies.

Real inductors have DC resistance (DCR) from the wire winding, which causes power loss as heat. The Q factor (quality factor) measures how 'ideal' the inductor is: Q = XL/DCR. Higher Q means lower losses. Ferrite-core inductors typically have Q = 20–80, while air-core inductors used in RF circuits can reach Q > 200.

Every inductor also has parasitic capacitance between its turns, forming an unintended LC circuit. This creates a self-resonant frequency (SRF) above which the inductor behaves like a capacitor. For reliable operation, always use inductors well below their SRF — a good rule is to stay below SRF/3.

Key Points

• XL = 2πfL — impedance increases linearly with frequency
• Energy stored: E = ½LI² — proportional to current squared
• Q = XL/DCR — higher Q means lower losses
• Above self-resonant frequency, inductor acts as a capacitor

Applications

• LC filters and impedance matching
• Switch-mode power supply energy storage
• EMI filtering and noise suppression
• RF tuning circuits and oscillators