Convert a value between units
API · /unit-api
Unit Converter API
Fast, deterministic unit conversion across 10 categories — length, mass, temperature, area, volume, speed, time, digital storage, pressure and energy. Convert any value between compatible units and list the full unit catalog per category. Fully local compute (no third-party upstream), so responses are instant and always available. Ideal for calculators, e-commerce, logistics, engineering tools, dashboards and chatbots.
API health
healthy- Uptime
- 100.00%
- Server probes · 24h
- Avg latency
- 87 ms
- Server probes · 24h
- Subscribers
- 3,366
- active
- Total calls
- 38
- last 7 days
Pricing
Pick a tier — billed monthly, cancel anytime.
Free
Free
- 12,000 calls / month
- 3 requests / second
- Hard cap (429 above quota, no overage)
- 12,000 conversions/mo, 3 req/s
- All 10 categories unlocked
- No credit card
Basic
€5.00 /month
- 350,000 calls / month
- 15 requests / second
- Hard cap (429 above quota, no overage)
- 350,000 conversions/mo, 15 req/s
- All 10 categories, commercial use
- Email support
Pro
€17.00 /month
- 2,000,000 calls / month
- 50 requests / second
- Hard cap (429 above quota, no overage)
- 2,000,000 conversions/mo, 50 req/s
- Batch conversion endpoint
- Priority email support
Mega
€44.00 /month
- 10,000,000 calls / month
- 150 requests / second
- Hard cap (429 above quota, no overage)
- 10,000,000 conversions/mo, 150 req/s
- 99.9% uptime SLA
- Priority support + dedicated key
Built by
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Currency Converter API
Live foreign-exchange conversion across 160+ world currencies — the plain, developer-friendly converter. Get the latest rates for any base currency, convert an amount between any two currencies, read the rate (and inverse) for a single pair, or list every supported currency. Rates are read live from an open exchange-rate source that aggregates a broad set of feeds and covers far more currencies than ECB-only data — including emerging-market and exotic currencies such as the Nigerian naira, Indian rupee or Vietnamese dong. This is the everyday convert / latest-rates utility a checkout, invoice, pricing page or travel app needs — distinct from the FX analytics APIs in the catalogue (historical date ranges, pip and position-size calculators, triangular-arbitrage path maths, currency indices), which compute on rates rather than simply converting them.
api.oanor.com/currencyconverter-api
Crypto Price & Converter API
Live crypto price and currency conversion, served from the public CoinGecko feed with no key and nothing cached. This is a conversion utility, distinct from market-overview, arbitrage and coin-profile tools: it tells you what a coin is worth right now and converts an amount between coins and fiats. The price endpoint returns the live price of one or more coins in one or more currencies at once, each with its market cap, 24-hour volume and 24-hour change — pull Bitcoin and Ethereum in USD, EUR and BTC in a single call. The convert endpoint converts an amount of a coin into a fiat currency or into another coin: two Bitcoin to euros, or one and a half Bitcoin to Ether, with the rate and the result. Coin-to-coin conversions are crossed through USD automatically. The supported endpoint lists every currency you can quote or convert into — dozens of fiats plus the major coins. Everything is read live from CoinGecko on each request, nothing stored beyond a short protective cache. Ideal for wallets, checkout and payment flows, portfolio trackers, price tickers and dashboards. Coin ids are lowercase CoinGecko ids (bitcoin, ethereum, solana). Live, no key. 3 endpoints. For prices by on-chain contract address use a token-price API.
api.oanor.com/cryptoconvert-api
Roman Numeral API
Roman numeral conversion as an API, computed locally and deterministically. The encode endpoint turns an integer from 1 to 3999 into its Roman numeral using standard subtractive notation, so 1994 becomes MCMXCIV and 2024 becomes MMXXIV. The decode endpoint turns a Roman numeral back into an integer with strict validation — it rejects malformed forms such as IIII or VV and also returns the canonical way to write the same value, accepting any letter case. The arithmetic endpoint adds, subtracts or multiplies two values given as either integers or Roman numerals and returns the result as a Roman numeral and as an integer, provided the result stays within the classic 1–3999 range. The standard subtractive pairs are IV, IX, XL, XC, CD and CM. Everything is computed locally and deterministically, so it is instant and private. Ideal for typesetting, publishing, education, clock-face, game and document-processing app developers, numbering and chapter tools, and history teaching. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is Roman numeral conversion; for binary, octal and hexadecimal number-base conversion use a base-conversion API.
api.oanor.com/roman-api
HTML to Markdown API
Convert HTML into clean GitHub-Flavored Markdown. Pass an HTML string, or a live page URL to fetch and convert, and get back tidy Markdown — headings, bold/italic, links, images, lists, blockquotes, code blocks, plus GFM tables, strikethrough and task lists. Script, style and head elements are stripped automatically. Tune the output: ATX or setext headings, the bullet marker, fenced or indented code blocks, inline or referenced links, and the emphasis/strong delimiters; toggle GFM on or off. The inverse of a Markdown-to-HTML renderer. Pure local conversion (the optional URL fetch aside) — no key, no third-party service, instant. Live. 3 endpoints. Built for content migration, web clipping and "save as Markdown", scraping cleanup, CMS import and documentation pipelines.
api.oanor.com/htmltomarkdown-api
Frequently asked questions
Quick answers about pricing, quotas, and integration.
How do I get an API key for Unit Converter API?
What's the rate limit for Unit Converter API?
How much does Unit Converter API cost?
Can I cancel my subscription anytime?
Is Unit Converter API GDPR-compliant?
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/unit-api/SOME_PATH \
-H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/unit-api/SOME_PATH", {
headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/unit-api/SOME_PATH");
curl_setopt($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/unit-api/SOME_PATH",
headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())
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