About Screen Ruler Online
What We Do
Screen Ruler Online is a free platform of browser-based measurement and utility tools. Everything runs directly in your browser — no install, no account, no paywall — and works on any modern phone, tablet, or computer.
The platform now hosts nine tools spanning measurement, screen testing, print, and decision-making. The flagship is the Screen Ruler itself — an accurate on-screen ruler in cm, mm, and inches that's reliable to within 0.5 mm once calibrated. The full lineup is documented in Our Free Online Tools below.
The measurement tools share a single calibration system — calibrate once for your screen and the setting is reused across the ruler, protractor, and pixel converter.
How It Works
Every screen has a unique pixel density measured in PPI (Pixels Per Inch). A 13-inch laptop screen and a 27-inch desktop monitor may share the same resolution, but their pixels are physically different sizes. Our calibration process measures this difference so the ruler can accurately convert screen pixels into real-world units.
We maintain a database of popular devices (iPhones, Samsung Galaxy phones, iPads, and more) with their known PPI values. When your device is recognized, we can provide instant measurements. For other devices, the credit card calibration method offers a reliable universal solution. You can read our full step-by-step guide for detailed instructions.
Who Uses Our Tools
The ruler is used in over 100 countries by designers verifying print dimensions, students measuring objects for homework, online shoppers checking product sizes, crafters cutting materials to size, and engineers doing quick physical measurements.
The protractor sees heavy use from woodworkers setting miter angles, sewers and patternmakers drafting darts and pleats, students learning geometry, photographers checking horizon tilt, and hobbyists measuring roof pitch or stair angles on small diagrams.
The spinner is popular with teachers running raffle picks, teams splitting tasks, gamers randomizing drafts, and families settling low-stakes decisions (movie nights, dinner choices).
Supported Devices and Browsers
Screen Ruler Online works in Chrome, Safari, Firefox, Edge, and any modern browser that supports standard web technologies. It runs on iPhones, Android phones, iPads, Android tablets, MacBooks, Windows laptops, Chromebooks, and desktop monitors. No plugins, extensions, or special permissions are needed.
Our device database includes pre-configured PPI values for iPhone 12 through iPhone 15, Samsung Galaxy S23 and S24 series, iPad Pro, iPad Air, iPad mini, Xiaomi Redmi, Realme, OPPO, Vivo, and Samsung Galaxy A-series devices popular in India, Indonesia, and Turkey.
Supported Languages
Screen Ruler Online is available in 20 languages: English, Chinese (Simplified and Traditional), Spanish, French, German, Japanese, Korean, Hindi, Vietnamese, Thai, Turkish, Indonesian, Malay, Filipino, Czech, Romanian, Croatian, Serbian, and Sinhala. We continue to add new languages based on user demand.
Calibration Objects
The ruler supports calibration with multiple reference objects to serve users worldwide: credit cards (ISO standard), US quarters, US pennies, 1 Euro coins, UK pound coins, Indian Rupee coins (5 and 10 denominations), Indonesian Rupiah 1000 coins, Turkish Lira coins, and A4 paper. Open the Screen Ruler and tap the calibration panel to pick from the full list with exact dimensions.
Ücretsiz Online Araçlarımız
Ölçüm, ekran testi, baskı ve karar verme için dokuz ücretsiz tarayıcı tabanlı araç. Hepsi tamamen tarayıcında çalışır — kurulum yok, hesap yok, paywall yok.
| Araç | Amaç | Şunlar için ideal | Fiyat |
|---|---|---|---|
| Screen Ruler | Fiziksel nesneleri cm/mm/inç olarak ölçmek için hassas ekran cetveli. | Tasarımcılar, alıcılar, küçük nesneleri ölçen öğrenciler | Ücretsiz |
| Yazdırılabilir Cetvel | Ücretsiz yazdırılabilir cetvel PDF'i — gerçek boyut, kalibrasyon gerekmez. | El işi, marangozluk, dikiş, çocuk ödevi | Ücretsiz |
| Cihaz Özellikleri | 69+ telefon, tablet ve dizüstü için ayrıntılı özellik veritabanı. | Mobil geliştiriciler, tasarımcılar, telefon alıcıları | Ücretsiz |
| Rastgele Çark | Kararlar, sınıf ve oyunlar için rastgele çark. | Öğretmenler, aileler, takım çekilişleri ve hediyeler | Ücretsiz |
| Ölü Piksel Testi | Ekranınızı ölü, takılı veya sıcak pikseller için 60 saniyede test edin. | Yeni ekran veya tamir alan herkes | Ücretsiz |
| İletki | 360°ye kadar açıları ölçen çevrimiçi iletki. | Geometri ödevi, marangozluk, dikiş, fotoğraf kontrolleri | Ücretsiz |
| Ekran Boyutu Hesaplayıcı | Çözünürlük ve DPI'den herhangi bir cihazın ekran boyutunu hesaplayın. | Ev sineması kuranlar, monitör alıcıları | Ücretsiz |
| Piksel Dönüştürücü | px değerini rem, em, pt, %, vw, vh'ye dönüştürün — anında CSS birim dönüştürücü. | Front-end geliştiriciler, CSS işi, baskı tasarımı ayarı | Ücretsiz |
| En Boy Oranı Hesaplayıcı | Video, görüntü ve ekranlar için en-boy oranlarını hesaplayın. | Video editörleri, sosyal medya tasarımcıları, görsel boyutlandırma | Ücretsiz |
Built by Developers, for Everyone
Screen Ruler Online started as a single tool — a calibration-based on-screen ruler — built by a team of web developers who needed a quick way to measure physical objects on screen during design reviews and hardware prototyping. Existing solutions were inaccurate, required downloads, or were cluttered with ads, so we built a clean one and made it free for everyone.
As we worked on the ruler we kept running into adjacent problems that also needed a simple, no-install web tool: measuring an angle on a photo, picking a random item from a short list. That is why the platform now includes a digital protractor and a random spinner alongside the ruler — each one small, focused, and free. The project is actively maintained and regularly updated with new device profiles, calibration objects, tool features, and language support.
Privacy & Data
Your calibration data is stored locally in your browser and is never sent to our servers. We use analytics to understand how people use the tool so we can improve it, but we do not collect any personal information. The ruler does not require an account, does not track individual users, and does not sell data to third parties. Read our full Privacy Policy for details.
Contact
Have a question, found a bug, or want to suggest a feature? We welcome your feedback. Leave us a message and we will get back to you.