A ruler for when the workshop is elsewhere
I’m a woodworker and a coder, and I can’t ever seem to find a ruler outside my workshop. So I made Screen Ruler.
The idea is straightforward: use the screen already in your hand to compare a small length, position a pair of calipers, check an angle or get a sense of level. The useful part is being able to calibrate the ruler to your own screen instead of trusting a generic picture of one.
What the site does
The on-screen ruler and calipers convert browser pixel distances into millimetres or inches using your chosen scale. The protractor compares the directions of two arms. The bubble level uses the device's orientation sensors where supported. Camera-based Big Ruler is a separate experimental feature for compatible WebXR devices.
These tools are convenient checks, with limitations that depend on the device and how you position it. Read Accuracy & calibration before treating a screen reading as a physical measurement, and follow the illustrated guide to get started.
The measuring guides cover the jobs I most often reach for a ruler for: checking against an object of known size, identifying screws and bolts, and converting inch fractions. Changes to the site are listed on What's new.
Device information
The local phone presets draw on device-specification data, including the Global Smartphone Database 2025, public manufacturer specifications and model-code aliases. Browser model hints and optional shared calibration templates can help select a starting scale. You can always calibrate manually.
Support Screen Ruler
Screen Ruler is free and will stay that way. If it saved you a trip to the shed, you can chip in any amount towards keeping it running. Payments go to ThinkSwift, my company, and are handled by Stripe.
Made by Geoffrey Bromilow
Find me on LinkedIn or GitHub. The Contact page explains what to include when reporting a problem.
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