Parallel inductors calculator
Two 10 H coils in parallel act as a single 5 H inductor, and 4, 6 and 12 H together give 2 H. Enter the inductance of each branch in henries and get the equivalent, always smaller than the smallest coil. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Inductors
- 10, 10
- Total
- 5 H
- Quantity
- 2
- Equivalent
- 5
- Reciprocal sum
- 0.2
This parallel inductors calculator returns the single equivalent inductance of two or more uncoupled inductors connected in parallel. The governing identity is one over Leq equals the sum of one over each branch inductance, so the total inductance equals one divided by the sum of the individual reciprocal inductances, reported in henries when the inputs are in henries. Parallel paths lower the total inductance: two equal coils of value L combine to L over two, and n equal coils of value L combine to L over n. Classic checks you may already know include ten henries in parallel with ten henries giving five henries, and four, six, and twelve henries combining to two henries. The engine uses only finite arithmetic with no network calls, no sampling, and no date-dependent shortcuts.
What inductors in parallel do and what the result shows
Inductors in parallel share the same voltage across every winding while the total current splits among the branches. Faraday's law still applies to each coil, but the combined magnetic energy storage behaves as a single equivalent inductance smaller than the smallest branch, because more parallel paths increase overall current for a given voltage rate of change.
Algebraically the rule is one over Leq equals the sum of one over each Li, which is the inductance analogue of the parallel-resistance conductance sum and is why two equal coils of L henries combine to L over two. A single positive inductor is valid and simply echoes that value as the total, which matches the limit case of the same formula. Negative inductance is also rejected because this tool models ordinary passive coils only, not active gyrators or sign-flipped models.
There is no series mode, no mutual coupling coefficient, no core-loss model, and no Monte Carlo sampling: the engine either evaluates the closed form inside the supported numeric range or rejects the input.
Where parallel Leq checks fit in study, design, and software
Students meet parallel inductance when a circuits unit introduces branch currents in RL networks, when a lab asks for the equivalent coil seen by a source, or when a contest problem gives several henry values and asks for the single equivalent without a full SPICE run. Filter designers combine chokes and radio-frequency coils in parallel to hit a target inductance that is not available as a single stock part, then check that the equivalent is still large enough to keep ripple current inside a converter limit.
Teachers can pre-generate answer keys for modest inductor sets without trusting opaque calculator apps that silently mix millihenries with henries or switch notation without saying so. Developers call the same contract from scripts to seed deterministic test vectors for schematic planners, to normalize user-entered coil networks before a bill-of-materials sketch, or to satisfy programming-challenge statements that demand Leq rather than a hand-waved estimate. Field technicians and makers use it for quick checks on LC filters, buck-converter input chokes, and audio crossover coils when only discrete inductor values are known.
What you can do with it
Homework and lab checks
Compute Leq for uncoupled parallel inductor networks before grading worksheets or RL lab write-ups that ask for a single equivalent in henries.
Filter and converter design
Combine stock choke values in parallel to hit a target inductance for LC filters, buck-converter input coils, and audio crossover networks.
FAQ
What does the parallel inductors calculator cost?
It is free in your browser on this page.
What formula is used for the equivalent inductance?
Two equal inductors of value L give L/2.
What happens if an inductance is zero or negative?
A zero-henry branch makes the 1/L term in the parallel formula undefined, and a negative henry is not a passive inductor in this model.
Does this tool also compute series inductance or mutual coupling?
No. It only evaluates the uncoupled parallel combination. Series equivalent inductance is the ordinary sum of the branch values; mutual inductance needs a coupling coefficient that this page does not accept.
Which units does the total inductance use?
The total is returned in henries (unit H) when every input is in henries. You may use any consistent unit (mH, µH) as long as every branch uses the same one; the numeric formula does not convert prefixes.
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/phys/parallel-inductors \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"inductors":[10,10]}'const res = await fetch("https://api.kit.forhosting.com/phys/parallel-inductors", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"inductors": [
10,
10
]
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/phys/parallel-inductors",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"inductors": [
10,
10
]
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/phys/parallel-inductors", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"inductors":[10,10]}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"inductors":[10,10]}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/phys/parallel-inductors", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"inductors": [
10,
10
]
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "phys.parallel_inductors",
"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_n | 1000 |
max_abs_henry | 1000000000000000 |
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
Any zero or negative inductance is rejected with invalid_input, because a zero-henry branch makes the reciprocal term undefined and a negative henry is not a passive inductor in this model.
What parallel inductance means and what the response contains
This calculator accepts a list of positive inductance values in henries and returns the normalized inductor array, the count of branches, the total equivalent inductance rounded to the requested precision, the same value echoed as equivalent, the reciprocal sum used as an intermediate, a short formula reminder, the method tag parallel_reciprocal, the precision used, and a unit hint of H for SI-consistent inputs. Zero inductance is never accepted: an ideal short-circuit inductance of zero henries would require a reciprocal of zero in the summation, so the request fails with invalid_input and a message that names the zero problem.
How inductor lists are read and how Leq stays reproducible
A comma or whitespace separated string is also accepted and split into the same numeric list. Each entry must be a positive finite decimal within the documented magnitude ceiling; embedded spaces inside a token, hex prefixes, and non-numeric junk are rejected with a clear message so a bad cell does not become a wrong equivalent. Zero and near-zero values fail explicitly because the parallel formula divides by each Li and a zero henry would make that reciprocal undefined. Negative values fail because a negative henry is not a physical passive inductor in this model. The preferred field is inductors, an array of finite numbers in henries or any consistent unit, but aliases values, L, inductances, henries, and list are accepted so spreadsheets, query strings, and typed forms can reuse the same contract. Empty arrays fail with invalid_input, and lists longer than the declared maximum count are rejected before any arithmetic runs. An optional precision field, with aliases decimals and dp, chooses how many decimal places to expose for the inductor list, the total, the equivalent, and the reciprocal sum, defaulting to ten and capped at fifteen so JSON goldens stay stable across runtimes. Pair the free browser run on this page with the priced API when you need the identical mathematical result inside an automated pipeline without re-implementing reciprocal sums yourself.
Where parallel Leq checks fit in study, design, and software
Product and education tools use the endpoint when a learner types a list of branch inductances and the interface must show the parallel equivalent and the reciprocal sum. On this page the work runs entirely in your browser; through the API each successful lookup costs $0.002, failed validation is not charged, and nothing is stored after the response returns. That split — free interactive exploration and a priced, identical API — matches the rest of the tier-A catalog and lets you move from a classroom demo to an automated pipeline without changing the mathematical result. Pair it with inductive-reactance or series helpers when you need related electrical steps, and with other physics endpoints when you are building a small lab of free, deterministic circuit calculators for study and software tests.
Integration use cases
Deterministic test fixtures
Generate reproducible parallel equivalents for unit tests, schematic demos, and CI assertions on 1/Leq = Σ(1/Li) without re-implementing the formula.