Screen Ruler

Screen Ruler runs directly in the browser, so you can finish common tasks quickly without installing extra software.

Free to useBrowser-basedDirect shareable URL

Drag rulers to position. Drag edges to resize.

Horizontal Length: 400px

Vertical Length: 300px

Hold a credit card (85.6mm wide) to the ruler and adjust until it matches.

Actual size on screen (px)

Known width (mm)

PPI: 96

100

200

300

400

400px / 105.8mm

100

200

300

300px / 79.4mm