Pixel density from resolution & diagonal
API · /ppi-api
Screen PPI API
healthy
3,799 Subscribers
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
API health
healthy- Uptime
- 100.00%
- Server probes · 24h
- Avg latency
- 81 ms
- Server probes · 24h
- Subscribers
- 3,799
- active
- Total calls
- 52
- last 7 days
Pricing
Pick a tier — billed monthly, cancel anytime.
Free
Free
- 10,135 calls / month
- 2 requests / second
- Hard cap (429 above quota, no overage)
- 10,135 calls/month
- 2 req/sec
- PPI + size + retina
- No credit card
Starter
€11.65 /month
- 19,750 calls / month
- 8 requests / second
- Hard cap (429 above quota, no overage)
- 19.75k calls/month
- 8 req/sec
- Dot pitch + aspect ratio
- Email support
Pro
€31.55 /month
- 247,500 calls / month
- 20 requests / second
- Hard cap (429 above quota, no overage)
- 247.5k calls/month
- 20 req/sec
- Display / AV pipelines
- Priority support
Mega
€69.55 /month
- 1,280,000 calls / month
- 50 requests / second
- Hard cap (429 above quota, no overage)
- 1.28M calls/month
- 50 req/sec
- Platform scale
- Dedicated SLA
Built by
Related APIs
Other APIs with overlapping tags.
DPI & Print Size API
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.
api.oanor.com/dpi-api
Mask API
Mask a value for safe display. The mask endpoint keeps the first and/or last few characters visible and replaces the rest with a mask character — so a card becomes ••••••••••••1111 and an API token becomes sk**********3456 — and can keep separators (spaces and dashes) intact so the value keeps its shape. A dedicated email masker hides the local part (and optionally the domain) while keeping the address recognisable, e.g. j•••••••@example.com. Choose how many characters to reveal and which mask character to use. Perfect for showing the last four digits of a card, partially hiding emails and phone numbers, and masking tokens and account numbers in UIs, receipts and logs. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This masks a known value for display; to find and redact PII inside free text, use a redaction API.
api.oanor.com/mask-api
Elevator Traction API
Traction-elevator engineering maths as an API, computed locally and deterministically — the counterweight, hoist-motor and rope-traction numbers a lift engineer or building-services designer sizes a passenger elevator with. The counterweight endpoint gives the balancing mass = the empty car plus a fraction of the rated load (the overbalance, typically 40–50 %, 45 % common), so a 1,000 kg car rated for 1,000 kg uses a 1,450 kg counterweight — the car and weight balance near half load and the machine is sized for the worst-case imbalance, not the full load. The motor-power endpoint uses that: because the counterweight cancels most of the car, the motor only lifts the out-of-balance load = rated load × (1 − overbalance), so power = that × g × speed ÷ efficiency (~65–75 % geared) — a 1,000 kg lift at 1.5 m/s needs only about 11–12 kW, half what a counterweight-less hoist would draw. The traction-ratio endpoint checks the friction grip: a traction elevator moves the ropes by friction over the sheave, so the available traction (e^(μθ), the capstan equation) must beat the T1/T2 tension ratio at both worst cases — a full car at the bottom and an empty car at the top — and it returns the governing ratio. Everything is computed locally and deterministically, so it is instant and private. Ideal for lift-design and building-services tools, vertical-transport and MEP utilities, and engineering calculators. Pure local computation — no key, no third-party service, instant. Sizing estimates — follow the lift code and maker data. 3 compute endpoints. For block-and-tackle use a pulley API; for capstan friction a capstan API.
api.oanor.com/elevator-api
Railway Tractive Effort API
Railway train-performance maths as an API, computed locally and deterministically — the tractive-effort, resistance and adhesion numbers a railway engineer, train planner or rail-sim developer rates motive power with. The tractive-effort endpoint gives the pulling force a locomotive develops = 375 × horsepower × efficiency ÷ speed (mph), the classic hyperbolic curve where a constant-power loco pulls hardest at low speed and tapers as it accelerates — 4,000 hp at 25 mph and 82 % efficiency is about 49,200 lbf at the rail. The resistance endpoint gives the forces a train fights: grade resistance ≈ 20 lb per ton per 1 % of grade (the weight component along the slope, the dominant force on a hill — a 5,000-ton train on a 1 % grade fights 100,000 lbf) plus curve resistance ≈ 0.8 lb per ton per degree of curve from flange friction. The adhesion endpoint gives the hard ceiling: however much power a loco has, it can only pull as hard as the wheels grip — maximum starting tractive effort = the adhesion coefficient (≈ 0.25 dry, more with sand) × the weight on the driving wheels, so 200 tons on the drivers is about 100,000 lbf before slip. Everything is computed locally and deterministically, so it is instant and private. Ideal for rail-operations and motive-power planning tools, train-simulator and railfan apps, and transport-engineering utilities. Pure local computation — no key, no third-party service, instant. Excludes the speed-dependent Davis rolling/air resistance. 3 compute endpoints. For highway curve geometry use a horizontal-curve API.
api.oanor.com/railway-api
Frequently asked questions
Quick answers about pricing, quotas, and integration.
How do I get an API key for Screen PPI API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Screen PPI API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Screen PPI 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 Screen PPI API cost?
Screen PPI API has a free tier with 100 calls / month. Paid plans start at €11.65 / 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 Screen PPI API GDPR-compliant?
All requests to Screen PPI 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/ppi-api/SOME_PATH \
-H "x-oanor-key: oanor_test_..."const res = await fetch("https://api.oanor.com/ppi-api/SOME_PATH", {
headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();$ch = curl_init("https://api.oanor.com/ppi-api/SOME_PATH");
curl_setopt($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/ppi-api/SOME_PATH",
headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())Ratings
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