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API · /number-api

Number API

healthy 4,754 Subscribers

A fast, fully-local number toolkit: spell numbers out in English words (great for amount-in-words on invoices and cheques), format ordinals (1st, 2nd, 112th), convert integers to and from Roman numerals (1 to 3999), convert numbers between any bases from 2 to 36, and format numbers locale-aware as decimal, currency or percent. Every endpoint accepts input via the query string or the request body. Pure server-side compute, no third-party upstream, so responses are instant and always available. Ideal for invoicing and billing, localization, education and developer formatting tooling.

#number #words #ordinal #roman #base-conversion #format #dev-tools
api.oanor.com/number-api
Get an API key Try in playground → Contact provider

Machine-readable spec so AI agents can integrate this API.

/api/number-api/openapi.json
/api/number-api/llms.txt

Discovery: GET /api/index.json lists every API.

Number API — live data on the oanor API marketplace

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
71 ms
Server probes · 24h
Subscribers
4,754
active
Total calls
95
last 7 days
status Full status page → · 15 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 17,000 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 17,000 calls/month, 2 req/s
  • All endpoints: words, ordinal, roman, base, format
  • No credit card
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Basic

€4.00 /month

  • 270,000 calls / month
  • 12 requests / second
  • Hard cap (429 above quota, no overage)
  • 270,000 calls/month, 12 req/s
  • All endpoints incl. Roman 1-3999 and base 2-36
  • Commercial use allowed
  • Email support
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Pro

€12.00 /month

  • 1,600,000 calls / month
  • 40 requests / second
  • Hard cap (429 above quota, no overage)
  • 1,600,000 calls/month, 40 req/s
  • Locale-aware decimal, currency and percent formatting
  • Priority email support
  • Commercial use allowed
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Mega

€32.00 /month

  • 8,500,000 calls / month
  • 150 requests / second
  • Hard cap (429 above quota, no overage)
  • 8,500,000 calls/month, 150 req/s
  • Full toolkit at scale, deterministic low-latency compute
  • Priority support
  • Commercial use allowed
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Built by

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PremiumApi

Related APIs

Other APIs with overlapping tags.

Wordle API — oanor API marketplace

Wordle API

A complete toolkit for Wordle-style word games: score a guess against a hidden answer and get the exact green/yellow/grey feedback pattern (with correct duplicate-letter handling), validate any word against the official dictionary, solve a puzzle from the clues collected so far (returns the remaining consistent answers and a suggested next guess that best narrows them down), pull a random answer word, and fetch the deterministic daily word for any date with its puzzle number. Built on the official answer list (2,315 words) and the full set of ~13,000 accepted guesses. Every endpoint accepts input via the query string or the request body and returns lean JSON. Pure server-side compute (no third-party upstream), so responses are instant and always available. Ideal for word-game backends, solvers and assistants, bots and educational apps.

api.oanor.com/wordle-api

 Words API — oanor API marketplace

Words API

Find words by meaning, sound and spelling — similar-meaning words (thesaurus), rhymes, autocomplete suggestions and wildcard spelling matches. Backed by Datamuse. Ideal for writing assistants, autocomplete, crosswords, word games, poetry tools and NLP preprocessing.

api.oanor.com/words-api

 Dictionary API — oanor API marketplace

Dictionary API

Look up English word definitions with phonetic transcriptions, pronunciation audio, parts of speech and example sentences, plus synonyms and antonyms. Ideal for writing tools, word games, language learning and education apps. Experimental support for 11 more languages.

api.oanor.com/dictionary-api

 Number Words API — oanor API marketplace

Number Words API

Format numbers in human-readable forms as an API. Spell any number in English words — handling thousands through quintillions, negatives and decimals (e.g. 1,234,567 → "one million two hundred thirty-four thousand five hundred sixty-seven", 12.56 → "twelve point five six"). Turn a whole number into its ordinal, both short (21 → 21st, 113 → 113th) and written out (twenty-first, one hundred thirteenth). And convert any whole number from 1 to 3999 to Roman numerals and back (2024 ⇄ MMXXIV), with strict validation. Everything runs locally, so it is fast and always available. Ideal for invoices, cheques and accounting, legal documents, internationalisation, accessibility (screen readers), education and any UI that turns digits into words.

api.oanor.com/numberwords-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Number API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Number API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Number API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Number API cost?
Number API has a free tier with 100 calls / month. Paid plans start at €4.00 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Number API GDPR-compliant?
All requests to Number API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/number-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/number-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/number-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/number-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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