Online Ruler

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Online Ruler
On-screen ruler with centimeter/inch scales. Since physical screen sizes vary, calibrate it once using a bank card (standard bank card width: 85.6 mm).
Measurement Unit
0
Calibration (place a physical bank card over the gray bar below and align its width exactly)
Reference: Standard bank card 85.6 mm
Instructions
  • The calibration value is saved in this browser. You do not need to calibrate again next time; recalibration is required when switching devices or browsers.
  • For more accurate measurements, place the object directly against the top edge of the screen and align it with the scale.
  • Measurement accuracy depends on the physical screen size and display scaling. Do not use the ruler when browser zoom is not set to 100%.

Screen ruler for centimeters and inches with bank card calibration

Online Ruler

The online ruler displays physical measurement scales directly on your computer, tablet, or phone screen. It supports both centimeters and inches and provides calibration using the standard 85.6 mm width of a bank card.

How to use the online ruler

Open the ruler and check the displayed centimeter or inch scale. Before measuring, calibrate the ruler using a standard bank card. Place the card against the calibration area and adjust the scale until the displayed reference length matches the real card width.

Why calibration is necessary

Different screens have different physical sizes, resolutions, and pixel densities. Therefore, the same number of screen pixels does not represent the same physical length on every device. Calibration improves the accuracy of the displayed scale.

What can it measure?

  • Bank cards and membership cards
  • Paper and photographs
  • Small electronic devices
  • Cables and small objects
  • Small packages and components

Accuracy

The accuracy depends on screen size, pixel density, browser zoom, and calibration. Keep the browser at 100 percent zoom after calibration. For precision measurements, use a physical ruler or professional measuring instrument.

Mobile devices

The ruler can be used on phones and tablets. Because every device has different screen characteristics, recalibration is recommended when switching devices or browsers.

What is an online ruler?

An online ruler displays centimeter and inch scales on a device screen and can be calibrated with an 85.6 mm standard bank card for everyday physical measurements.
  • Support centimeter and inch measurements
  • Work on computers, phones, and tablets
  • Calibrate the screen using an 85.6 mm standard bank card
  • Measure paper, cards, and other small objects
  • Save calibration settings locally in the browser
  • Recalibrate when changing devices or browsers
  • Keep browser zoom at 100 percent after calibration
  • Use a professional measuring tool for high-precision work
Calibration can make screen measurements more practical, but accuracy depends on the device and calibration. Use a physical measuring instrument when precise dimensions are required.
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