Online Ruler

Calibrate against a standard bank card, then use a screen ruler with millimeter and inch markings.

Units

Calibration multiplier

Calibration reference — match this bar to the long edge of a standard bank card (85.60 mm)

85.60 mm reference

Default 96 CSS pixels per inchPhysical screen size cannot be detected reliably by browsers. Calibrate for accurate real-world measurements on your specific display and zoom level.

How to use this Online Ruler

Measure on-screen lengths in centimeters and inches with optional physical calibration. Enter your values above and the result is calculated directly in your browser. No account is required.

Fast answer, clear inputs

This tool is built around one job: give the answer quickly without forcing a signup or hiding the result. Related tools are linked nearby when the next calculation or conversion is useful.