# Zyougi.com — Real-Size Browser Ruler for Smartphones > Free, browser-based virtual ruler calibrated to the exact screen dimensions of each supported smartphone model. No app download or registration required. Works in Safari, Chrome, and any modern mobile browser. ## What This Site Does Zyougi.com provides pixel-accurate on-screen rulers by using the precise PPI (pixels per inch) of each supported device. Unlike generic online rulers that estimate screen size, every ruler on this site is built for a specific model. Users place an object against the screen and read the measurement directly — in centimeters or inches. **Accuracy:** Calibrated per device model PPI. On iPhone and iPad, the calibration was verified against a physical ruler and measures within 0.5 mm under normal conditions (no screen protector distortion). Android values are calculated from published PPI and device pixel ratio using the same formula, but have not been individually verified on physical hardware. **Supported devices:** iPhone 5 through iPhone 17 Pro, iPad, iPad mini, Google Pixel (6a through 10 Pro), Samsung Galaxy S21+5G, Sony Xperia 10 III, Sharp AQUOS sense 4, and more. **Additional tools:** Protractor, printable PDF rulers (up to 1 m), ring size measurement, unit converter, visual acuity test, spirit level, instrument tuner, sound level meter, hearing age check. ## Key Pages ### Japanese (ja) - [Home](https://zyougi.com/) - [iPhone 17 Ruler](https://zyougi.com/iphone17/) - [iPhone 16 Ruler](https://zyougi.com/iphone16/) - [iPhone 15 Ruler](https://zyougi.com/iphone15/) - [iPhone 14 Ruler](https://zyougi.com/iphone14/) - [Android Ruler (general)](https://zyougi.com/android/) - [Pixel 10 Pro Ruler](https://zyougi.com/android_pixel10pro/) - [Pixel 10 Ruler](https://zyougi.com/android_pixel10/) - [Pixel 9a Ruler](https://zyougi.com/android_pixel9a/) - [About / Accuracy & Calibration](https://zyougi.com/about/) - [Knowledge: Ruler vs. Measure](https://zyougi.com/mametishiki/) ### Japanese (ja) — Measurement tools - [Protractor](https://zyougi.com/bundoki/) - [Printable Ruler (PDF, up to 1 m)](https://zyougi.com/print/) - [Ring Size Tool](https://zyougi.com/ring/) - [Unit Converter (cm / inch / shaku)](https://zyougi.com/tani/) - [Sound Level Meter / Decibel Tool](https://zyougi.com/decibel/) - [Spirit Level / Tilt Meter](https://zyougi.com/suiheiki/) - [Instrument Tuner](https://zyougi.com/tuner/) - [Mouse DPI Checker](https://zyougi.com/dpi/) - [Hearing Age Check (mosquito tone)](https://zyougi.com/choryoku/) ### Japanese (ja) — Vision tests - [Visual Acuity Test](https://zyougi.com/shiryoku/) - [Color Vision Test](https://zyougi.com/shiryoku/color/) - [Presbyopia Test](https://zyougi.com/shiryoku/rougan/) - [Kinetic Visual Acuity Test](https://zyougi.com/shiryoku/doutai/) - [Astigmatism Test](https://zyougi.com/shiryoku/ranshi/) - [Dynamic Vision Test](https://zyougi.com/dynamic-vision/) ### Japanese (ja) — Reaction and input tests - [Ability Test Index](https://zyougi.com/game/) - [Reaction Time Test](https://zyougi.com/reaction/) - [CPS / Click Speed Counter](https://zyougi.com/cps/) - [Timing Accuracy Test](https://zyougi.com/timing/) - [Memory Test](https://zyougi.com/memory/) - [Aim Accuracy Test](https://zyougi.com/aim/) - [FPS Sensitivity Converter (eDPI, cm/360)](https://zyougi.com/sensitivity/) ### English (en) - [Home (English)](https://zyougi.com/en/) - [iPhone 17 Ruler (English)](https://zyougi.com/en/iphone17/) - [iPhone 16 Ruler (English)](https://zyougi.com/en/iphone16/) - [iPhone 15 Ruler (English)](https://zyougi.com/en/iphone15/) - [Android Pixel 10 Pro (English)](https://zyougi.com/en/android_pixel10pro/) - [Android Pixel 10 (English)](https://zyougi.com/en/android_pixel10/) ## Frequently Asked Questions **Is this ruler free?** Yes. No sign-up, no download, no app required. Open the page on your smartphone browser and start measuring immediately. **Why is this more accurate than other online rulers?** Most online rulers guess your screen size, which causes errors. Zyougi.com is calibrated for each specific device model using its exact screen dimensions and pixel density (PPI), giving real-size measurements in cm or inches. **Do I need to install an app?** No. Open in Safari (iPhone) or Chrome (Android). You can add it to your home screen for app-like access without installing anything. **Which devices are supported?** iPhone 5 through iPhone 17 Pro, all iPad and iPad mini models, and Android phones including Google Pixel, Samsung Galaxy, Sony Xperia, Sharp AQUOS, and more. There are 43 model-specific pages plus two auto-detecting pages (one for iPhone, one for Android). **How is the on-screen ruler calibrated?** Every device renders a CSS pixel at a different physical size, so a single fixed image cannot be actual-size everywhere. Zyougi.com displays the same ruler image at a display height chosen individually for each model. For iPhone and iPad, those per-model values were set by holding a physical ruler against the real device and adjusting until the markings matched, not by calculation alone. For Android, the sheer number of models makes physical verification of every device impractical, so values are calculated from each model's published pixel density (PPI) and device pixel ratio (DPR) using the formula derived from the verified iPhone measurements. Android readings should therefore be treated as calculated rather than hardware-verified. **What can make the on-screen ruler inaccurate?** Four things change the physical size of a CSS pixel and will throw off the reading: 1. iPhone Display Zoom set to "Larger Text" / "Zoomed" (Settings → Display & Brightness → Display). Use the standard setting. 2. Android display size changed from its default (Settings → Display → Display size). 3. Browser zoom, including pinch-to-zoom. Reset to 100%. 4. A thick screen protector or glass, which adds a gap between the object and the screen surface. Full details: https://zyougi.com/about/ ## License Quoting and referencing this site's content is welcome, including inside AI-generated answers, provided the source URL is credited. Reproducing a page in full, or copying the structure and design of the site, is not permitted. This matches the site policy published at https://zyougi.com/sitepolicy/ (Japanese) and https://zyougi.com/en/sitepolicy/ (English).