LC resonant frequency calculator
1 mH with 1 µF resonates at about 5033 Hz, roughly 5 kHz. Enter the inductance in henries and the capacitance in farads to get the natural frequency of an ideal, undamped tank, plus its angular frequency and period. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Inductance
- 0.001
- Capacitance
- 0.000001
- Inductance
- 0.001
- Capacitance
- 0.000001
- F0
- 5,032.9212104487
- Frequency
- 5,032.9212104487
An LC resonant frequency calculator turns coil inductance and capacitor value into the natural frequency of an ideal tank circuit.
What resonance means in an ideal LC circuit
In elementary AC circuit theory, an ideal series or parallel combination of inductance L henries and capacitance C farads has a natural resonant angular frequency omega zero equals one over the square root of L C, measured in radians per second. The ordinary frequency in hertz is f zero equals omega zero over two pi, which expands to the closed form f zero equals one over two pi times the square root of L C.
At that frequency the inductive and capacitive reactances have equal magnitude, energy sloshes between the magnetic field of the coil and the electric field of the capacitor, and the ideal undamped tank oscillates freely. Doubling L or C multiplies the period by square root of two and halves the frequency by the same factor; both values must stay strictly positive because a shorted inductance or an open capacitance leaves no finite product under the radical.
Typical classroom numbers: one millihenry with one microfarad resonates near five kilohertz; one hundred millihenry with one microfarad sits near about five hundred hertz—easy to check by hand once units are consistent. Teachers and automated graders care about the zero-L and zero-C rejections as much as the arithmetic: a student who plugs L equals zero has left the domain of the formula, and a silent absolute-value fallback would hide that mistake.
Practical tips, limits, and related searches
Keep inductance and capacitance inside the published absolute range so their product under the square root cannot underflow to a zero root that would make f0 non-finite, and so the resulting frequency stays within the published magnitude cap. Convert millihenries by dividing by one thousand, microhenries by one million, microfarads by one million, and picofarads by one trillion before you call if you want f0 already in hertz without mental rescaling afterward.
Prefer this capability when you already have scalar L and C and only need the ideal undamped resonant frequency; if your source is a multi-stage filter, convert each stage to henries and farads first. Round-trip checks are easy: recompute one over two pi times square root of L C by hand and confirm it equals the published f0 within the same twelve-decimal rounding, and confirm that scaling L and C by the same factor k multiplies the period by square root of k as the formula predicts.
What you can do with it
Homework checks for LC tank frequency
Students enter L and C from textbook tank-circuit problems and compare hand-written f0 against a deterministic result before submitting.
Filter and oscillator pre-flight estimates
Designers estimate undamped tank resonance before budgeting bandwidth, Q, or component tolerances in LC stages.
FAQ
What happens when inductance is zero?
Zero inductance is outside this model—the formula diverges.
Does this include resistance or damping?
No. It returns the ideal undamped f0, ω0, period, formula, equation, and substitution steps only. Use a dedicated RLC tool for damped poles or Q.
Is the LC resonant frequency calculator free?
The browser tool is free and runs locally.
What happens to the resonant frequency if I double the capacitor?
It falls by a factor of the square root of two, and the period grows by the same factor. Doubling the inductance has exactly the same effect, because only the product of L and C sits under the square root.
How do I enter microfarads or picofarads?
Convert to farads and henries first: divide microfarads by one million and picofarads by one trillion, and divide millihenries by 1000 or microhenries by one million. The frequency then comes out directly in hertz.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/elec/lc-resonant-frequency \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"L":0.001,"C":0.000001}'const res = await fetch("https://api.kit.forhosting.com/elec/lc-resonant-frequency", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"L": 0.001,
"C": 0.000001
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/elec/lc-resonant-frequency",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"L": 0.001,
"C": 0.000001
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/elec/lc-resonant-frequency", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"L":0.001,"C":0.000001}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"L":0.001,"C":0.000001}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/elec/lc-resonant-frequency", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"L": 0.001,
"C": 0.000001
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "elec.lc_resonant_frequency",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Limits
max_abs | 1000000000000 |
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Inductance and capacitance must both be strictly positive: zero L or zero C would send the classical formula to infinity, so the API returns a clear invalid_input error instead of inventing Infinity or NaN.
What f0 = 1 / (2 π √(L C)) means for an ideal LC tank
Prefer SI throughout: convert millihenries to henries and microfarads to farads before the call so comparisons stay consistent. The check path recomputes one over two pi square root of L C with the same fixed rounding used for published fields, so a successful response always ships with steps you can assert in tests or worksheets without floating-point ambiguity between the Worker and the browser.
How to call the API and what comes back
Prefer sending numbers rather than pre-formatted strings when you control the client; string numbers are accepted only when they match a strict finite numeric pattern including optional scientific notation. Send a JSON body with two required finite numbers: L (aliases inductance, henry, and henries) for inductance in henries, and C (aliases capacitance, farad, and farads) for capacitance in farads. Absolute values must stay within the published limit of one trillion so intermediate products and roots remain finite in IEEE double precision on the Worker and in the browser. Both L and C must be strictly positive; values whose absolute magnitude is at or below one times ten to the minus fifteen are treated as zero and rejected, and any strictly negative L or C is also invalid_input for this ideal passive tank model. On success the response echoes rounded L and inductance, C and capacitance, sets f0, frequency, and resonant_frequency to the same positive hertz value, omega0 and angular_frequency to one over square root of L C in rad/s, T and period to one over f0 in seconds, formula to the string f0 equals one over two pi square root of L C, equation to a human-readable substitution line, unit_f0 to Hz, unit_omega0 to rad/s, unit_T to s, unit_L to H, unit_C to F, message to a short English summary, and steps to an ordered array of given values, formula, product, square root, omega line, substitution, period, and summary. Failed validation—missing fields, non-numeric strings, non-finite numbers, values outside absolute limits, zero or negative L, zero or negative C, or a non-finite root—returns invalid_input and is never charged. Pricing is a flat $0.002 per successful request with unit item and zero marginal unit price.
Practical tips, limits, and related searches
When teaching, pair examples: L equals zero point zero zero one henry with C equals one times ten to the minus six farad yields about five thousand thirty-three hertz; scaling L or C by four halves f0; setting L to zero demonstrates the hard invalid_input path for zero inductance; and setting C to zero demonstrates the zero-capacitance rejection. This landing targets people searching for an LC resonant frequency calculator, tank circuit frequency, or f0 equals one over two pi square root of L C online; it is not an RLC damped natural-frequency tool, not a quality-factor or bandwidth calculator, not an inductive or capacitive reactance solver, and not a full impedance analyzer. Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when learners deliberately set inductance or capacitance to zero.
Integration use cases
Unit tests for RF and filter solvers
Generate known-good f0 cases plus deliberate zero-L and zero-C rejections for coding kata expected values.
Technical questions
What is the resonant frequency of an LC circuit?
For ideal inductance L henries and capacitance C farads, the resonant frequency is f0 = 1/(2π√(LC)) hertz, with angular frequency ω0 = 1/√(LC) rad/s.
What happens when capacitance is zero?
Zero capacitance is likewise rejected with invalid_input; both L and C must be strictly positive.