LC Resonant Frequency Calculator
Enter any two of f / L / C to solve the third, plus the characteristic impedance Z₀.
What it does: Compute the resonant frequency of an LC tank, or work back to the inductor/capacitor you need.
When to use it: When designing oscillators, tuned tanks, LC filters or frequency-selective networks.
At the resonant frequency, the reactance? of the inductor and capacitor cancel each other.
MEANS The tank resonates at this frequency; the characteristic impedance is about —.
Common cases pre-computed: browse LC resonance presets →
No history yet. Each calculation is automatically saved to this device.
How to use the LC resonance calculator
Pick the unknown → enter the other two → read f₀ and Z₀.
- 01
Pick the value to solve for
Click f / L / C to choose which is unknown; the selected field becomes the result box.
- 02
Enter the other two
Supports
100u,100n,10p,455knotation (µ/n/p/k/M prefixes). - 03
Read the resonant frequency and Z₀
The result updates live and also gives the characteristic impedance Z₀ = √(L/C). Expand to see the formula with values substituted in.
Common resonance combinations
A few typical LC values and their resonant frequencies for quick reference when estimating.
| L | C | f₀ ≈ | Use case |
|---|---|---|---|
| 100 µH | 100 nF | 50.3 kHz | Low-frequency oscillation / filtering |
| 100 µH | 220 pF | 1.07 MHz | AM medium-wave band |
| 10 µH | 10 pF | 15.9 MHz | Shortwave / HF |
| 25 µH | 1.0 nF | 1.01 MHz | IF tuning |
Computed from f₀ = 1/(2π√(LC)) (ideal, lossless).
Common questions, answered in 3 minutes
What does this frequency mean?
It is the resonant frequency f₀ of the LC tank — at this frequency the reactances of the inductor and capacitor cancel and the tank impedance reaches an extreme (maximum for a parallel tank, minimum for a series tank).
What is Z₀ (characteristic impedance) good for?
Z₀ = √(L/C) reflects the tank's energy-storage character. For the same f₀, a larger L/C ratio gives a higher Z₀, which affects frequency selectivity and the quality factor (Q).
Why does the real resonance point differ from the computed one?
This tool assumes an ideal, lossless LC. Real inductors have DC resistance, capacitors have losses, and there are parasitics, which shift the resonance slightly and introduce bandwidth — for precise design, factor in the part datasheets and the Q value.
Do series and parallel LC use the same formula?
The resonant frequency f₀ formula is the same; the difference is the impedance at resonance: series shows minimum impedance, parallel shows maximum impedance.
Can I work backwards and choose components from a frequency?
Yes. Switch "Solve for" to L or C, enter the target frequency and the other known component value, and it computes the required inductor or capacitor.
Standards and sources referenced by this tool
| Item | Value / Formula | Source |
|---|---|---|
| Resonant frequency | f₀ = 1/(2π√(LC)) | Thomson formula (ideal LC) |
| Characteristic impedance | Z₀ = √(L/C) | LC tank surge impedance |
Ideal, lossless LC formula, no external API.