Centimeter scale and metric divisions
Each centimeter is divided into 10 millimeters. A major centimeter mark therefore represents 10 mm, while the smaller divisions provide a convenient way to estimate tenths of a centimeter.
How to measure in centimeters
- Set browser zoom to 100%.
- Open the ruler and select cm.
- Calibrate against a known physical reference when the physical size matters.
- Align one edge of the object with the 0 mark.
- Read the centimeter position or place a measurement guide at the opposite edge.
Using a known reference
A compatible ISO/IEC 7810 ID-1 card has nominal dimensions of 85.60 mm × 53.98 mm and can be used as a convenient calibration reference. A physical ruler with a known length works as well.
Use the reference to establish the scale for the screen you are actually using. Do not assume the same centimeter scale remains valid after changing displays or materially changing browser zoom or display scaling.
When centimeter mode is useful
Everyday sizing
Compare small objects, labels, paper elements, crafts, and household items.
Layout work
Use calibrated physical units when a design or placement needs a real-world reference.