LC Resonant Frequency Calculator — Tank Circuit
Find the frequency at which an LC tank circuit naturally oscillates: enter the inductance and capacitance to get the resonant frequency, period, angular frequency, and characteristic impedance.
mH
µF
Frequency at which inductive and capacitive reactances cancel
- 1
Inductance in henries
1 × 10⁻³ = 0.001 H - 2
Capacitance in farads
1 × 10⁻⁶ = 0.000001 F - 3
Resonant frequency
1 ÷ (2π × √(0.001 × 0.000001)) = 5,032.92At this frequency, inductive and capacitive reactances cancel.
How does this calculator work?
The LC resonant frequency is f = 1/(2π√(LC)). Enter inductance in mH and capacitance in µF to get the frequency in Hz, the period, angular frequency ω = 2πf, and the characteristic impedance Z₀ = √(L/C). At this frequency, inductive and capacitive reactances cancel and the circuit can sustain oscillation.
Formula
How this is calculated
An LC tank circuit consists of an inductor (L, in henries) and a capacitor (C, in farads) connected in parallel or series. At one specific frequency — the resonant frequency — the inductive reactance XL = ωL exactly equals the capacitive reactance XC = 1/(ωC). Setting XL = XC and solving for ω gives ω₀ = 1/√(LC), so the resonant frequency is f₀ = ω₀/(2π) = 1/(2π√(LC)).
At this frequency, energy alternates between the magnetic field of the inductor and the electric field of the capacitor, sustaining oscillation. In a lossless circuit (zero resistance) the oscillation persists indefinitely; in real circuits a resistive Q-factor Q = Z₀/R determines how quickly energy dissipates. The characteristic impedance Z₀ = √(L/C) (ohms) governs the ratio of peak voltage to peak current during oscillation and is important for filter and impedance-matching design.
This calculator assumes an ideal lossless LC pair. In practice, the inductor winding resistance and capacitor ESR introduce losses and slightly shift the frequency, especially at low Q. For most RF and audio design purposes, f₀ = 1/(2π√(LC)) gives excellent accuracy.
Frequently asked questions
Enter inductance in millihenries (mH) and capacitance in microfarads (µF). For higher frequencies, you may have µH inductors and pF capacitors — convert: 1 mH = 1 000 µH, 1 µF = 1 000 000 pF. Then scale your entry (e.g., 0.001 mH for 1 µH, or 0.000001 µF for 1 pF).
Frequency is inversely proportional to both L and C. To double the frequency, reduce either L or C by a factor of 4 (since f ∝ 1/√(LC)). Variable capacitors (varactors or trimmers) are the most common way to fine-tune radio circuits. Use this calculator in reverse: fix one component value and read the required other value from the formula C = 1/(L·(2πf)²).
Z₀ = √(L/C) is the ratio of peak voltage to peak current at resonance and determines the Q-factor when loss resistance R is known: Q = Z₀/R. Higher Z₀ relative to R gives sharper, higher-Q resonance peaks, useful in narrow bandpass filters. It also matters for impedance matching between stages.
Also known as
TG we-Calculate Editorial Team. (2026). LC Resonant Frequency Calculator — Tank Circuit [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/resonant-frequency-lc-calculator
TG we-Calculate Editorial Team. "LC Resonant Frequency Calculator — Tank Circuit." TG we-Calculate. 2026. https://we-calculate.com/calculator/resonant-frequency-lc-calculator.
TG we-Calculate Editorial Team, "LC Resonant Frequency Calculator — Tank Circuit," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/resonant-frequency-lc-calculator
@misc{wecalculate_resonant_frequency_lc_calculator, title = {LC Resonant Frequency Calculator — Tank Circuit}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/resonant-frequency-lc-calculator}}, year = {2026}, note = {TG we-Calculate} }
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