Yuzool

Online ruler

Measure small things on your screen at real size, once you have matched it to a bank card.

0.0 cm

Put one end of the thing you're measuring on the zero line, then drag the other handle to its far end. Drag the zero line too, to measure between two marks. Calibration is saved on this device.

About the online ruler

This ruler shows real centimetres and inches on your screen. Screens differ in how many pixels they fit into a centimetre, and browsers don't tell a web page, so the ruler asks you to calibrate it once with something everyone has: a bank card.

Every bank, debit, credit and most ID and loyalty cards are the same size, 85.60 × 53.98 mm (the ISO/IEC 7810 ID-1 size). Match the drawn card to a real one and the ruler is accurate on that screen. The calibration is saved on this device.

How to use it

  1. Tap Calibrate. Hold a card flat against the screen in the top corner of the drawn card.
  2. Drag the corner handle (or use the slider and the + and − buttons) until the drawn card matches the real one exactly. Tap Done.
  3. Put one end of the object on the zero line and drag the other handle to its far end.
  4. Read the length between the handles. Drag the zero line too, to measure between two marks.

Good for

  • Checking the size of a screw, bolt or drill bit
  • Measuring a ring, a button or a coin
  • Sizing a photo print or a stamp
  • Measuring a part for a replacement when you have no ruler to hand

Questions

How do I make the online ruler actual size?

Calibrate it with a bank card. Cards are all 85.60 by 53.98 mm, so once the drawn card matches a real one, the ruler measures true centimetres and inches on that screen.

Why isn't a web ruler accurate without calibration?

Browsers measure in CSS pixels, not real millimetres, and the number of pixels per centimetre differs between screens. Before calibration the ruler uses a guess and says Not calibrated.

Does it work on a laptop?

Yes. Calibrate with a card held against the laptop screen, gently, and measure small objects held up to it.

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