Online Ruler

Online Ruler is a free set of measuring tools that run entirely in your browser. Its actual-size screen ruler shows centimeter, millimeter and inch scales, and a calibration step fixes the usual problem of on-screen rulers being wrong on phones and high-DPI displays: match the outline to an ISO/IEC 7810 ID-1 bank card (85.60 x 53.98 mm) or enter your screen diagonal. Drag along the ruler to read a distance in mm, cm and inches at once, use top, left or right rulers or full screen. An image measurement tool reads lengths and angles from a photo, and a converter handles mm, cm, m, inches, feet and pixels. No account; nothing is uploaded.