Screen Measuring Tools
Use your screen as a ruler. Calibrate once with a card or coin and measure at real size
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A set of tools that turn a phone or monitor screen into a ruler when no ruler is at hand. After one screen calibration you can measure length, diameter, bolt size, ring size, angles and more at real size.
How to use
- On your first visit, press "Start screen calibration", hold a card or a coin against the screen until the outline matches it exactly, and press "Save this size".
- Under "What do you want to measure", choose the tool that fits the object.
- For a quick length, line up the end of the object with the 0 mark of "A ruler ready to use" and read the scale.
How it works
- You can calibrate with a card, a coin, a banknote, a standard object, the screen size or your own ruler. The calibration is saved in this browser on this device and is used by every measuring tool.
- Browser zoom is corrected automatically, so drawings stay at real size.
- Only objects that lie flat against the screen can be measured accurately. With thick or round objects the reading changes with the viewing angle.
Questions and answers
- Can I measure length with my phone?
- Yes. After calibrating with a card or a coin, the screen shows real-size marks. A careful match is accurate to about 1 mm, for objects shorter than the screen.
- Why is a bank card used for calibration?
- Credit, debit and most ID cards share one standard size, 85.6 × 53.98 mm, so they work as a reference everywhere. A coin or a banknote can be used instead.
- Do I need to calibrate every time?
- No. Once saved, the calibration stays in the same browser on the same device. Another device or another browser needs its own calibration.