Permutation & Combination Calculator API GET

Documentation Start for free →

Calculate permutations (P(n,r)) and combinations (C(n,r)) for any given values of n and r.

Try it — live request, no key required

Request

GETapi.apiverve.com/v1/permutationcombination

Verification

Format

No key required to try it. Get a key to use it in your app.

200 OK

{
  "status": "ok",
  "error": null,
  "data": {
    // Permutation & Combination Calculator response payload
  }
}

About the Permutation & Combination Calculator API

Perfect for probability calculations, statistics problems, and combinatorial analysis in mathematics.

What people use it for

Education: Solve permutation and combination problems for homework and exams
Probability: Calculate odds and probabilities in statistics
Programming: Determine algorithm complexity and counting problems
Game Design: Calculate possible combinations for game mechanics

Ways to call it

One endpoint, many ways in — REST with JSON, XML, YAML and CSV, plus GraphQL and an MCP interface for AI agents.

JSON: Default REST response
XML: Markup format
YAML: Human-readable
CSV: Tabular export
GraphQL: Query language
MCP: For AI agents

View all integrations →

Other ways to use Permutation & Combination Calculator

Same data, same APIVerve account, same credit balance — one key works on all of them.

Give it to an AI agentConnect over MCP and your agent calls it as a native tool — Claude, Cursor, ChatGPT.on VerveKit Google Sheets or ExcelA =VERVE() formula fills a column — no script, no export, recalculates in place.on VerveSheets Ground an agent on itA cited, machine-checkable fact your model can't produce on its own.on VerveContext

Questions.

Common questions about the Permutation & Combination Calculator API.

Read the docs →

What does the Permutation & Combination Calculator API do?

Calculate permutations (P(n,r)) and combinations (C(n,r)) for any given values of n and r.

How do I authenticate Permutation & Combination Calculator API requests?

Pass your API key in the x-api-key header over HTTPS. One key works across all 300+ APIVerve APIs — there are no per-endpoint credentials.

How much does the Permutation & Combination Calculator API cost?

Each call spends 2 credits from your shared pool. The free tier includes 200 credits every month, and paid plans add more headroom.

How fast is the Permutation & Combination Calculator API?

Response time depends on the endpoint — the p50 through p99 latency for this API is published on this page. Requests are served over HTTPS through a global edge network.

What response formats does the Permutation & Combination Calculator API support?

JSON by default, plus XML and YAML via the format parameter. GraphQL and an MCP interface for AI agents are available across the catalog.

What HTTP method does the Permutation & Combination Calculator API use?

GET over HTTPS, following standard REST conventions with a consistent { status, error, data } response envelope.

Request parameters — GET /v1/permutationcombination

Sent in the query string. Premium parameters are accepted on every plan but only take effect on plans that include them. Anything not listed here is dropped rather than passed through.

Required

Parameter	Type	Example	Description
`n`Required	integer	`10`	Total number of items range 0-170
`r`Required	integer	`3`	Number of items to choose (must be <= n) range 0-170

Example request

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curl "https://api.apiverve.com/v1/permutationcombination?n=10&r=3" \
  -H "x-api-key: YOUR_API_KEY"

Authentication

Send your key in the x-api-key header. That is the only auth step — no token exchange, and no per-endpoint scope to configure.

Header	When	Value
`x-api-key`Required	Every request	Your API key. Header names are case-insensitive, so `X-API-Key` is the same header.
`Authorization`Alternate	Instead of the above	`Bearer <key>` — for clients that only expose bearer auth. Resolves to the same account and the same billing.

401 is the only auth verdict

A 401 means the key is missing, invalid or expired. A 403 means the key is valid but not permitted here — blocked by a key restriction or an IP allow-list. Running out of credits is a 429.

Response — GET /v1/permutationcombination

Every APIVerve endpoint returns the same three top-level keys, so one response handler covers your whole integration: status, error and data. Only data changes shape.

Sample response

{
  "status": "ok",
  "error": null,
  "data": {
    "n": 10,
    "r": 3,
    "permutation": 720,
    "combination": 120,
    "formulas": {
      "permutation": "P(n,r) = n! / (n-r)!",
      "combination": "C(n,r) = n! / (r! × (n-r)!)"
    }
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Field	Type	Example	Description
`n`	number	`10`	Total number of items used in calculation
`r`	number	`3`	Number of items chosen in calculation
`permutation`	number	`720`	Calculated permutation P(n,r) result value
`combination`	number	`120`	Calculated combination C(n,r) result value
`formulas`Premium	object	`{...}`	Object containing mathematical formulas for permutation and combination
`permutation`Premium	string	`"P(n,r) = n! / (n-r)!"`	Mathematical formula used for permutation calculation
`combination`Premium	string	`"C(n,r) = n! / (r! × (n-r)!)"`	Mathematical formula used for combination calculation

Response headers

Every response carries your balance, so your own code always knows where it stands without polling anything. All four are exposed to browsers through CORS.

Header	What it carries
`x-api-remaining-credits`	Credits left in the current cycle
`x-api-credits-used`	Credits spent in the current cycle
`x-api-max-credits`	The allowance for the cycle
`x-api-version`	Version of the endpoint that answered

Errors

Read the HTTP status first, then error for the specific reason. The body names the parameter that has to change.

Status	Meaning	What to do
`400`	Input was rejected	Read `error`; it names the parameter that has to change.
`401`	Key missing or invalid	Check the header name and the key value.
`403`	Key valid, but not permitted here	A key restriction or an IP allow-list — never a bad key.
`429`	Rate limited, or out of credits	Read `error` to tell them apart, then back off or top up.

What a call costs — 2 credits per call

Credits are shared across every APIVerve API — one balance, one key, one bill. Failed requests never count against it, so a rejected input costs nothing.

Plan	Per month	Credits	Permutation & Combination Calculator calls	Per 1,000 calls
Free	Free	200	100	Free
Starter	$29.99	200,000	100,000	$0.30
Pro	$99.99	1,000,000	500,000	$0.20
Mega	$299.99	4,000,000	2,000,000	$0.15

Calls are what the credits buy at this API's rate — spend them here, on any of the other APIs, or across both. Nothing is reserved per endpoint.

Compare all pricing tiers →

Call it from cURL — GET /v1/permutationcombination

No SDK to install — this is a plain HTTPS call to /v1/permutationcombination with your key in the x-api-key header. Swap in a real key and it runs as-is.

cURL

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curl "https://api.apiverve.com/v1/permutationcombination" \
  -H "x-api-key: YOUR_API_KEY"

Resources

GitHubapiverve/permutationcombination-apiSource, issues and the examples this page is built from.ReferencePermutation & Combination Calculator API docsEvery parameter, every response field, and the errors.ParametersWhat this call acceptsRequired and optional inputs, with example values.

Also published for

@apiverve/permutationcombinationnpm APIVerve.API.PermutationCombinationCalculatorNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from Node.js — GET /v1/permutationcombination

Install the Node.js SDK, then call the Permutation & Combination Calculator API with your key. The client wraps the same HTTPS request, so anything it returns is what the endpoint returns.

Install — npm

npm install @apiverve/permutationcombination

Node.js

const res = await fetch("https://api.apiverve.com/v1/permutationcombination", {
  headers: { "x-api-key": "YOUR_API_KEY" },
});
const { data } = await res.json();
console.log(data);

Resources

npm@apiverve/permutationcombinationThe published Node.js client, versioned and signed.GitHubapiverve/permutationcombination-apiSource, issues and the examples this page is built from.ReferencePermutation & Combination Calculator API docsEvery parameter, every response field, and the errors.ParametersWhat this call acceptsRequired and optional inputs, with example values.

Also published for

APIVerve.API.PermutationCombinationCalculatorNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from Python — GET /v1/permutationcombination

No SDK to install — this is a plain HTTPS call to /v1/permutationcombination with your key in the x-api-key header. Swap in a real key and it runs as-is.

Python

import requests

res = requests.get(
    "https://api.apiverve.com/v1/permutationcombination",
    headers={"x-api-key": "YOUR_API_KEY"},
)
print(res.json()["data"])

Resources

Also published for

@apiverve/permutationcombinationnpm APIVerve.API.PermutationCombinationCalculatorNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from C# / .NET — GET /v1/permutationcombination

Install the C# / .NET SDK, then call the Permutation & Combination Calculator API with your key. The client wraps the same HTTPS request, so anything it returns is what the endpoint returns.

Install — NuGet

dotnet add package APIVerve.API.PermutationCombinationCalculator

C# / .NET

using var client = new HttpClient();
client.DefaultRequestHeaders.Add("x-api-key", "YOUR_API_KEY");

var json = await client.GetStringAsync("https://api.apiverve.com/v1/permutationcombination");
Console.WriteLine(json);

Resources

NuGetAPIVerve.API.PermutationCombinationCalculatorThe published C# / .NET client, versioned and signed.GitHubapiverve/permutationcombination-apiSource, issues and the examples this page is built from.ReferencePermutation & Combination Calculator API docsEvery parameter, every response field, and the errors.ParametersWhat this call acceptsRequired and optional inputs, with example values.

Also published for

@apiverve/permutationcombinationnpm

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from Go — GET /v1/permutationcombination

No SDK to install — this is a plain HTTPS call to /v1/permutationcombination with your key in the x-api-key header. Swap in a real key and it runs as-is.

req, _ := http.NewRequest("GET", "https://api.apiverve.com/v1/permutationcombination", nil)
req.Header.Set("x-api-key", "YOUR_API_KEY")

res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))

Resources

Also published for

@apiverve/permutationcombinationnpm APIVerve.API.PermutationCombinationCalculatorNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from PHP — GET /v1/permutationcombination

No SDK to install — this is a plain HTTPS call to /v1/permutationcombination with your key in the x-api-key header. Swap in a real key and it runs as-is.

PHP

$ch = curl_init("https://api.apiverve.com/v1/permutationcombination");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-api-key: YOUR_API_KEY"]);

$response = curl_exec($ch);
echo $response;

Resources

Also published for

@apiverve/permutationcombinationnpm APIVerve.API.PermutationCombinationCalculatorNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

Call it from Ruby — GET /v1/permutationcombination

No SDK to install — this is a plain HTTPS call to /v1/permutationcombination with your key in the x-api-key header. Swap in a real key and it runs as-is.

Ruby

require "net/http"

uri = URI("https://api.apiverve.com/v1/permutationcombination")
req = Net::HTTP::Get.new(uri)
req["x-api-key"] = "YOUR_API_KEY"

res = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |h| h.request(req) }
puts res.body

Resources

Also published for

@apiverve/permutationcombinationnpm APIVerve.API.PermutationCombinationCalculatorNuGet

Only the languages APIVerve ships a client for are listed — the rest call the endpoint directly over HTTPS.

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Permutation & Combination Calculator API GET

Try it — live request, no key required

About the Permutation & Combination Calculator API

What people use it for

Ways to call it

Other ways to use Permutation & Combination Calculator

Questions.

Request parameters — GET /v1/permutationcombination

Required

Authentication

Response — GET /v1/permutationcombination

Response fields

Response headers

Errors

What a call costs — 2 credits per call

Call it from cURL — GET /v1/permutationcombination

Resources

Also published for

Call it from Node.js — GET /v1/permutationcombination

Resources

Also published for

Call it from Python — GET /v1/permutationcombination

Resources

Also published for

Call it from C# / .NET — GET /v1/permutationcombination

Resources

Also published for

Call it from Go — GET /v1/permutationcombination

Resources

Also published for

Call it from PHP — GET /v1/permutationcombination

Resources

Also published for

Call it from Ruby — GET /v1/permutationcombination

Resources

Also published for

Zero-code embed — one snippet, no backend

Changelog — Permutation & Combination Calculator API

Math/Calculations

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