About Live Ruler

We built Live Ruler because every online ruler we could find was either inaccurate, ugly, feature-poor, or all three. Measuring something on screen should be as simple as opening a webpage — and the result should be correct.

Why Accuracy Matters

Most "online rulers" assume your screen has 96 pixels per inch (PPI). That number was a reasonable default in 2005. Today, screens range from 82 PPI (a 27″ 1080p monitor) to 460+ PPI (a modern flagship phone). Using a ruler calibrated to the wrong PPI is like using a ruler that's been stretched — every measurement is wrong, and you won't know it until something doesn't fit.

Live Ruler solves this with four calibration methods, from automatic device detection to the gold-standard credit card method, where you match a physical reference object to an on-screen outline. Once calibrated, your settings persist so you never have to repeat the process.

What Makes Us Different

We studied every competing online ruler and built the tool that does everything the best of them does — rulers on all four edges, guide lines, crosshair coordinates, dark mode, fullscreen, keyboard shortcuts — and then added features none of them offer: named calibration profiles, side-by-side object comparison, and a printable true-to-scale PDF ruler.

Live Ruler is a static website. Your calibration data never leaves your browser. There are no accounts, no tracking pixels, and no ads. The tool loads fast and works offline once cached.

Built By

Live Ruler is made by HTech. If you have feedback, feature requests, or found a bug, reach us at our contact page.