📏 On-Screen Ruler & Pixel-to-Physical Converter

Turn your screen into a ruler. Calibrate once with a bank card (85.6 mm wide) or by entering your screen's diagonal size, then measure real objects in mm, cm and inches — and convert between CSS pixels, physical pixels, points, mm and inches for design work.

Step 1 — calibrate

Hold a bank card against the screen and slide until it matches:

BANK CARD · 85.60 mm

…or enter screen diagonal (inches):

Step 2 — measure (drag on the ruler, or use the box)

Drag to measure Units:

Resizable measuring box

drag corner ↘

Unit converter (uses your calibration)

CSS px Device px mm inches pt (1/72 in) CSS "in" (96px)