---
title: "Calculates the resonant frequency of an LC circuit, along with optional Q factor and bandwidth when series resistance is provided. The resonant frequency f0 = 1/(2*pi*sqrt(L*C)) is where inductive and capacitive reactances cancel. Used for designing tank circuits, oscillators, bandpass filters, and antenna matching networks. If resistance R is given, computes quality factor Q = (1/R)*sqrt(L/C) and 3 dB bandwidth = f0/Q. Chain into impedance_match to design matching networks at the resonant frequency."
method: POST
path: "/api/lc_resonance"
tags: ["pcb"]
---

# Calculates the resonant frequency of an LC circuit, along with optional Q factor and bandwidth when series resistance is provided. The resonant frequency f0 = 1/(2\*pi\*sqrt(L\*C)) is where inductive and capacitive reactances cancel. Used for designing tank circuits, oscillators, bandpass filters, and antenna matching networks. If resistance R is given, computes quality factor Q = (1/R)\*sqrt(L/C) and 3 dB bandwidth = f0/Q. Chain into impedance_match to design matching networks at the resonant frequency.

`POST /api/lc_resonance`

## Request

- Base URL: `https://calc.engineer`
- URL: `https://calc.engineer/api/lc_resonance`
- Auth: none declared

## Request body

- object
  - `inductance_h` number, required: Inductance in henries (H). The inductive element of the LC circuit.
  - `capacitance_f` number, required: Capacitance in farads (F). The capacitive element of the LC circuit.
  - `resistance_ohm` number: Optional series resistance in ohms for Q factor and bandwidth calculation. Omit for ideal LC analysis.

## Response `200`

Computed result for lc_resonance

- object
  - `result` object, required
    - `resonant_freq_hz` number, required: Resonant frequency in hertz.
    - `resonant_freq_mhz` number, required: Resonant frequency in megahertz for convenience.
    - `angular_freq_rad` number, required: Angular resonant frequency in radians per second (omega_0 = 2*pi*f0).
    - `impedance_at_resonance_ohm` number, nullable, required: Impedance at resonance in ohms. Equals the series resistance R if provided; null if ideal (no R).
    - `q_factor` number, nullable, required: Quality factor Q = (1/R)*sqrt(L/C). Null if no resistance provided.
    - `bandwidth_hz` number, nullable, required: 3 dB bandwidth in hertz (f0/Q). Null if no resistance provided.
  - `tool` string, required
  - `version` string, required
  - `computed_at` string, date-time, required
  - `chain` object, required
    - `feeds` unknown[]
      - unknown
    - `accepts_from` unknown[]
      - unknown

## Other responses

- `400`: Validation error or invalid JSON
- `404`: Tool not found

---

[API](https://skmtc.dev/calc/apis/calc-engineer-api.md) · [All operations](https://skmtc.dev/calc/apis/calc-engineer-api/llms.txt) · [OpenAPI document](https://skmtc.dev/calc/apis/calc-engineer-api/revisions/8830480ec488?raw)