Company
About Real Size Ruler
Real Size Ruler is a free web tool that turns the screen you already have into a ruler you can trust. No app to install, no account to create, nothing to buy.
Why we built it
Most rulers on the web are drawn in pixels, and a pixel is a different physical size on every phone, tablet and monitor. A “1 inch” line on one screen can be half an inch on another. We wanted an online ruler that measures real objects correctly, so we made calibration the first step instead of an afterthought.
What we care about
- Accuracy. Three calibration methods (Auto-Detect, Screen Diagonal and Credit Card) bring readings to within a millimetre or two over 10 cm.
- Privacy. Your calibration and preferences stay in your browser. We don’t use accounts or tracking cookies. Read the privacy policy for details.
- Simplicity. Inches, centimeters and millimeters, guide lines, a measuring box and a true-size grid, all usable with a mouse, a finger or the keyboard.
- Access for everyone. The ruler is free, works in any modern browser and is available in 12 languages.
Who it’s for
Anyone who needs a quick measurement without a physical ruler nearby: checking a screw or a bead, sizing a ring or a photo print, confirming a product’s dimensions before ordering, or helping a student learn to read fractions of an inch.
Get in touch
Found a device that calibrates incorrectly, or have an idea for a feature? We’d like to hear from you on our contact page.