Screen Ruler
A ruler at actual size on your screen, calibrated with a bank card: measure an object in cm or inches, find a ring size, see a coin or a sheet at 1:1
Calibration
A browser doesn't know the size of your screen's pixels. Measure once with a card, and the ruler is right on this screen from then on.
Match my edges
Hold any card the size of a bank card (ID card, driving licence, loyalty card) flat against the screen, its corner in the outline's top-left corner, and resize the outline until it matches the card's edges. The arrow keys on the slider fine-tune it.
inches
Enter the diagonal of the screen, between 3 and 120 inches.
Kept for this screen only, in your browser. Leave the browser's zoom at 100%: on Safari, zooming changes the sizes without the page knowing.
Ruler
Lay the object against the screen from the top-left corner. Drag across the ruler to measure between two points; in full screen, it covers the whole screen.
Ring size
Lay a ring that fits on the circle and resize it until the circle's line just shows inside the ring. A finger is a little larger in the evening and in the heat.
Actual size
×
mm