LC Resonant Frequency Calculator
Enter inductance and capacitance to calculate the ideal resonant frequency of an LC tank circuit.
If you work with oscillators, filters, RF circuits, or power electronics, knowing the resonance frequency of an LC circuit is essential. This LC circuit frequency calculator helps you quickly find the theoretical resonance point from two values: inductor (L) and capacitor (C).
What Is LC Resonance?
An LC circuit contains an inductor and capacitor that exchange energy between magnetic and electric fields. At one specific frequency, the reactance of the inductor and capacitor are equal in magnitude and opposite in sign. This is called the resonant frequency. In an ideal lossless circuit, resonance is very sharp and energy transfer is maximum.
Core Formula
f = 1 / (2π√(LC))
where f is frequency in hertz (Hz), L is inductance in henries (H), and C is capacitance in farads (F).
How to Use This Calculator
- Enter the inductor value and select its unit (H, mH, µH, nH, pH).
- Enter the capacitor value and select its unit (F, mF, µF, nF, pF).
- Click Calculate Frequency.
- Read the resonant frequency, angular frequency, and period.
The calculator automatically converts your values to base SI units and then applies the resonance equation. This prevents manual conversion errors and speeds up circuit design calculations.
Worked Example
Suppose your circuit has:
- Inductor: 10 µH
- Capacitor: 100 nF
Converting to SI units:
- L = 10 × 10-6 H
- C = 100 × 10-9 F
Plugging into the formula gives a resonance near 159.15 kHz. This is a common range for switching and signal-conditioning applications.
Typical LC Value Ranges and Frequency Bands
| Inductance | Capacitance | Approx. Resonance Range | Common Use |
|---|---|---|---|
| 1 mH | 1 µF | ~5 kHz | Audio filters |
| 100 µH | 10 nF | ~159 kHz | SMPS / control circuits |
| 10 µH | 100 pF | ~5.03 MHz | RF tuning |
| 100 nH | 10 pF | ~159 MHz | VHF front-end networks |
Important Real-World Notes
1) Component Tolerance Matters
Real inductors and capacitors are not perfect. A ±5% component tolerance can shift resonance significantly, especially at high frequencies.
2) Parasitic Elements Shift Resonance
PCB traces, inductor winding resistance, capacitor ESR, and stray capacitance all affect actual circuit behavior. The calculated value is an ideal starting point, not a guaranteed measured result.
3) Temperature and Bias Effects
Capacitance can vary with temperature and DC bias (notably in some ceramic dielectrics). Inductor core materials can also change with temperature and current.
When You Might Use an LC Frequency Calculator
- Designing a tank circuit oscillator
- Tuning an RF band-pass or band-stop filter
- Estimating resonant behavior in wireless power links
- Checking expected switching ripple characteristics
- Learning electronics and verifying hand calculations
Quick FAQ
Is this calculator for series and parallel LC circuits?
Yes, for ideal components the resonance frequency formula is the same for both series and parallel LC combinations.
Can I use µH and pF directly?
Yes. Choose the correct unit from the dropdowns and the calculator will convert automatically.
Why does my measured frequency differ from the result?
Differences usually come from tolerance, parasitics, instrument loading, or non-ideal component behavior at high frequency.
Final Thoughts
The LC circuit resonance formula is simple, but getting fast and reliable answers depends on clean unit handling and consistent workflow. Use this calculator to move quickly from concept to prototype, then validate with simulation and measurement for production-level confidence.