Resonant LC Calculator
Compute resonant frequency, inductance, or capacitance for an ideal LC tank circuit using:
Rearranged:
L = 1 / ((2πf)2C) and C = 1 / ((2πf)2L)
Tip: Use positive values only. This tool assumes ideal components (no losses).
What is an LC resonant circuit?
An LC circuit is a combination of an inductor (L) and a capacitor (C) that naturally oscillates at a specific frequency. This frequency is called the resonant frequency. At resonance, magnetic energy in the inductor and electric energy in the capacitor exchange back and forth with minimal external input.
Why use a resonant LC calculator?
In electronics design, quickly solving for f, L, or C saves time and reduces mistakes. Engineers and hobbyists use LC resonance calculations for:
- RF tuning circuits and filters
- Oscillator design
- Impedance matching networks
- Sensor and antenna front-end circuits
- Educational lab experiments
How to use this calculator
1) Choose what to solve for
Select frequency, inductance, or capacitance from the dropdown. The selected field becomes the computed value.
2) Enter the two known values with units
Add your known values and choose their units (Hz/kHz/MHz/GHz for frequency, H/mH/µH/nH for inductance, and F/mF/µF/nF/pF for capacitance).
3) Click Calculate
The result is displayed in your selected unit plus a convenient auto-scaled engineering unit for quick interpretation.
Example calculations
Example A: Find resonant frequency
If L = 10 µH and C = 100 nF, then:
f = 1 / (2π√(LC)) ≈ 159.15 kHz.
Example B: Find inductance
If f = 1 MHz and C = 220 pF:
L = 1 / ((2πf)2C) ≈ 115 µH.
Design notes and real-world limits
Real components are not ideal. Inductors have series resistance and parasitic capacitance. Capacitors have ESR, leakage, and tolerance variation. These factors shift practical resonance and reduce Q factor.
- Use tolerance-aware components for precision tuning.
- Expect resonance to move with temperature and frequency.
- At high frequencies, PCB layout parasitics can dominate.
- Verify final results using simulation and measurement.
Common mistakes to avoid
- Mixing up nF and pF by three orders of magnitude.
- Using zero or negative values.
- Forgetting that formulas assume ideal LC behavior.
- Ignoring stray capacitance and inductor self-resonance.
Quick takeaway
The resonant LC calculator helps you move from concept to implementation quickly. Use it for fast first-pass design, then refine with realistic models and bench validation.