LC Resonant Tank Calculator
Calculate resonant frequency, required capacitance, or required inductance for an ideal LC tank circuit. Optional resistance lets you estimate quality factor and bandwidth.
What is a resonant tank circuit?
A resonant tank circuit is an electrical network made from an inductor (L) and capacitor (C) that naturally oscillates at a particular frequency called the resonant frequency. At that frequency, energy moves back and forth between the magnetic field of the inductor and the electric field of the capacitor.
LC tanks appear everywhere in electronics: radio tuners, RF filters, impedance matching stages, oscillators, and wireless power systems. If you can quickly calculate L, C, and resonance, you can design and debug a huge range of analog and RF circuits.
Core equations used by this calculator
ω₀ = 2πf₀ = 1 / √(LC)
C = 1 / ((2πf₀)²L)
L = 1 / ((2πf₀)²C)
XL = ω₀L, XC = 1/(ω₀C)
Z₀ = √(L/C)
Qseries ≈ ω₀L / Rs, BW ≈ f₀ / Q
How to use the calculator
1) Choose the variable you want to solve
- Resonant Frequency (f₀): enter L and C.
- Capacitance (C): enter L and target frequency.
- Inductance (L): enter C and target frequency.
2) Pick engineering units directly
You can mix practical units such as µH, pF, and MHz. The tool converts everything to SI internally, performs the math, and displays readable engineering results.
3) Optionally include resistance
If you enter series resistance, the calculator estimates Q factor and 3 dB bandwidth. These are first-order estimates for quick design checks.
Design tips for real-world LC resonance
- Component tolerance matters: 5% capacitors and inductors can shift frequency significantly.
- Parasitics are real: PCB trace capacitance and inductor self-capacitance can detune high-frequency designs.
- Q depends on losses: winding resistance, dielectric losses, ESR, and nearby conductive objects lower Q.
- Temperature drift: use stable dielectric capacitors (like C0G/NP0) where drift is critical.
- Measure and trim: for RF work, final calibration often requires a VNA, scope, or frequency counter.
Worked example
Suppose you have L = 10 µH and C = 100 pF. The resonant frequency is:
f₀ = 1 / (2π√(LC)) ≈ 5.03 MHz
If your series resistance is 2 Ω:
- Q ≈ ω₀L/R ≈ 158
- Bandwidth BW ≈ f₀/Q ≈ 31.8 kHz
This indicates a relatively narrow and selective resonant response, useful for tuned RF stages.
Where resonant tank calculations are used
- AM/FM and shortwave tuning circuits
- Crystal and LC oscillator startup analysis
- Band-pass and notch filter center frequency setup
- RF impedance matching and antenna tuning networks
- Inductive charging and resonant power transfer systems
Quick takeaway
The resonant tank circuit is one of the most powerful building blocks in electronics. With accurate LC resonance frequency calculations, plus practical checks on Q and bandwidth, you can move from rough concept to reliable hardware much faster.