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2026-05-04 15:53
Why I Built an Online Ruler That Needs Calibration
Most "online ruler" pages look simple: draw a rectangle, add centimeter ticks, add inch ticks, done.
That works only if every screen maps CSS pixels to real-world size in the same way. They do not.
A 13-inch laptop, a 27-inch external monitor, a phone, a tablet, and a 4K display can all render the same CSS width with different physical sizes. Browser zoom, operating-system scaling, Retina-style ...