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API · /dpi-api

DPI & Print Size API

healthy 3,639 Subscribers

Resolution, print-size and pixel-density maths for print, design, photography and screens. The resolve endpoint takes any two of pixels, DPI and physical length and computes the third, returning the size in inches, centimetres, millimetres and points — so you can answer "how big will a 3000-pixel image print at 300 DPI" or "what DPI do I get printing 3000 px at 10 inches". The ppi endpoint computes a screen's pixel density from its resolution and diagonal size, plus the dot pitch in millimetres, the total megapixels and the aspect ratio. The convert endpoint converts a length between pixels, inches, centimetres, millimetres and points (PostScript points, 1/72 inch), using a DPI when pixels are involved. Everything is computed locally and deterministically, so it is instant and private. Ideal for print and prepress, graphic and web design, photography, and screen and display specs. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. This is DPI and print-size maths; for aspect ratios and resizing use an aspect-ratio API and for general unit conversion use a unit API.

#dpi #ppi #print-size #resolution #design #developer-tools
api.oanor.com/dpi-api
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Machine-readable spec so AI agents can integrate this API.

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

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

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
74 ms
Server probes · 24h
Subscribers
3,639
active
Total calls
52
last 7 days
status Full status page → · 12 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 6,535 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 6,535 calls/month
  • 2 req/sec
  • Resolve + PPI + convert
  • No credit card
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Starter

€8.05 /month

  • 16,050 calls / month
  • 8 requests / second
  • Hard cap (429 above quota, no overage)
  • 16.05k calls/month
  • 8 req/sec
  • in / cm / mm / pt / px
  • Email support
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Pro

€27.95 /month

  • 211,500 calls / month
  • 20 requests / second
  • Hard cap (429 above quota, no overage)
  • 211.5k calls/month
  • 20 req/sec
  • Prepress / design pipelines
  • Priority support
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Mega

€65.95 /month

  • 1,100,000 calls / month
  • 50 requests / second
  • Hard cap (429 above quota, no overage)
  • 1.1M calls/month
  • 50 req/sec
  • Platform scale
  • Dedicated SLA
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Related APIs

Other APIs with overlapping tags.

Screen PPI API

Screen and display pixel-density maths as an API, computed locally and deterministically. The ppi endpoint computes the pixels per inch of a display from its resolution and diagonal size — along with the pixels per centimetre, the dot pitch in millimetres, the diagonal in pixels, the total pixels and megapixels, the simplified aspect ratio, and the physical width and height. The size endpoint does the inverse: from a resolution and a known PPI it works out the physical dimensions and diagonal in inches and centimetres. The retina endpoint analyses a display at a viewing distance: it computes the pixels per degree, says whether the display is effectively "retina" (pixels indistinguishable to 20/20 vision, around 60 pixels per degree), and gives the distance at which it becomes retina. Everything is computed locally and deterministically, so it is instant and private. Ideal for display and monitor tools, AV and signage planning, UI and responsive-design work, and hardware comparison sites. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is screen pixel density; for print resolution and image-to-print sizing use a DPI API.

api.oanor.com/ppi-api

Golden Ratio & Scale API

Design-proportion maths as an API, computed locally and deterministically. The divide endpoint splits a length by the golden section, the division beloved of artists and designers in which the whole is to the longer part as the longer is to the shorter, both ratios equal to φ = (1+√5)/2 ≈ 1.618 — so 100 splits into a 61.8 longer segment and a 38.2 shorter one — and can also extend a single segment to its larger or smaller golden partner. The rectangle endpoint gives the other side and the area of a golden rectangle from either side, the shape that leaves a smaller golden rectangle when you remove a square. The scale endpoint builds a modular (typographic) scale — base · ratio^step across a range of steps up and down — for harmonious type sizes and spacing, taking a numeric ratio or a named musical one such as minor-third (1.2), major-third (1.25), perfect-fourth (1.333) or golden (φ); a 16-base major-third scale gives 16, 20, 25, 31.25 and so on. Lengths are unit-agnostic. Everything is computed locally and deterministically, so it is instant and private. Ideal for graphic-design, web-design, UI, typography, layout and architecture app developers, type-scale and proportion tools, and design systems. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is proportion and scale; for pixel-density and print sizing use a PPI/DPI API.

api.oanor.com/goldenratio-api

Color Distance API

CIE colour science as an API: convert colours through the device-independent spaces and measure how different two colours really look. The convert endpoint takes a colour as hex, RGB or CIELAB and returns it in sRGB hex, RGB, CIE XYZ and CIELAB (D65 white point). The distance endpoint computes the perceptual difference between two colours with all three standard Delta-E formulas — CIE76 (plain Lab distance), CIE94, and CIEDE2000, the modern and most accurate metric — and tells you whether the difference is perceptible. The nearest endpoint finds the closest named colour to any colour by CIEDE2000. This is the maths behind colour matching, print and brand-colour QC, and tolerancing — distinct from simple hex/RGB/HSL conversion. Everything is computed locally and deterministically, so it is instant and private. Ideal for print and prepress, brand-colour compliance, textile and paint matching, image processing and computer vision, and design tooling. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. This is CIE colour difference; for hex/RGB/HSL/CMYK conversion, palettes and WCAG contrast use a colour API.

api.oanor.com/colordelta-api

Color Name API

Name any colour. The nearest endpoint takes a colour as a hex, an rgb() value, an r,g,b triple or another name and returns the closest of the 140+ CSS named colours — matched perceptually with CIE76 Lab distance, not naive RGB, so the name actually looks right — along with the distance and whether it is an exact match. The name endpoint resolves a CSS colour keyword (e.g. rebeccapurple, cornflowerblue) to its hex and RGB, and list returns the whole named-colour set. Perfect for design tools and pickers, accessibility and theming, turning brand hex codes into human labels, and naming colours in generated palettes. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. Distinct from colour conversion / palette / contrast tooling, which does not name colours.

api.oanor.com/colorname-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for DPI & Print Size API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call DPI & Print Size API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for DPI & Print Size 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 DPI & Print Size API cost?
DPI & Print Size API has a free tier with 100 calls / month. Paid plans start at €8.05 / 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 DPI & Print Size API GDPR-compliant?
All requests to DPI & Print Size 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/dpi-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/dpi-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/dpi-api/SOME_PATH");
curl_setopt($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/dpi-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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