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Coil Self Resonant Frequency Calculator
Estimate an inductor or coil self-resonant frequency from inductance and parasitic capacitance, then compare it with the intended operating frequency.
Input Parameters
Results
Equations Used
Self Resonant Frequency: fSRF = 1 / (2π√(LCp))
Inductive Reactance: XL = 2πfL
Q Estimate: Q = XL / Rseries
Operating Ratio = fop / fSRF
Frequently Asked Questions (FAQ)
Q1: What is coil self resonant frequency?
It is the frequency where inductance resonates with parasitic capacitance and the component stops behaving like an ideal inductor.
Q2: Why should operating frequency stay below SRF?
Near and above SRF, impedance behavior changes and the coil may become capacitive.
Q3: How much margin is recommended?
Many designs keep operating frequency well below SRF, often below 20–30% of SRF depending on application.
Q4: Where does parasitic capacitance come from?
It comes from winding-to-winding capacitance, package structure, PCB pads, and nearby conductors.
Q5: Does this calculate real inductor impedance?
No. It is a simplified RLC estimate. Datasheet impedance curves are better for final selection.
Q6: Can this be used for RF coils?
Yes for a first estimate, but RF coils require layout and measurement verification.
