True-size scale, angle gauge and a daily size-guessing game.
Drag the A and B handles, or focus one and press the arrow keys. Shift makes the step ten times larger. Only the visible length can be measured.
Drag the arms around the dial, or focus one and use the arrow keys (Shift for 10 degrees). The angle gauge does not depend on calibration.
How long is it?
Drag the knob or use the arrow keys (Shift for bigger steps), then lock in. The scale is logarithmic, so a 10 percent miss costs the same on a coin as on a sheet of paper. Sizes are the standard published dimensions.
| Object | You | Actual | Miss |
|---|
Hold a bank card (or any ID-1 card, 85.60 by 53.98 mm) flat against the screen. Line one edge up with both ends of the bar, then adjust the size until they match.
Screens vary in real pixel density, and browser zoom changes it too. This page cannot read your screen's physical size, so the scale is only as accurate as your calibration, usually within a millimetre or two when you match carefully. Your calibration stays on this device and adjusts itself if the zoom level changes. For anything that matters, check against a physical measuring tool.