Screen Ruler and Pixel Measure
100% PrivateProductivity ToolsMeasure anything on screen in pixels by drawing a box around it.
Runs entirely in your browser. Your input is not uploaded to Ovatly or anywhere else.
Drag on the area below to draw a measurement box. Pixel counts are exact. Millimetre and centimetre readouts are estimates from the standard CSS reference size (96 pixels per inch) until you calibrate with a bank card below.
Hold a bank or ID card against the screen and move the slider until the bar below is exactly as wide as the card, then press Calibrate. Until then, physical sizes on this page are estimates.
- 1Drag across the measuring area to draw a box; the readout appears below it.
- 2Read the width, height and diagonal in pixels: those numbers are exact.
- 3For physical sizes, hold a bank card to the screen, move the calibration slider until the bar matches the card's width, and press Calibrate.
- 4Measure again: millimetre and centimetre figures now use your screen's real pixel density.
You draw a box 300 pixels wide. Before calibration, at the standard CSS reference of about 3.78 pixels per millimetre, the ruler estimates 79.4 mm. You then calibrate with a bank card and your screen turns out to run at 5 pixels per millimetre; the same 300 pixel box now reads 60 mm, which is its true size on your display.
- Pixel measurements are exact; physical measurements are only as good as the calibration. Browser zoom and operating system display scaling change the true pixels-per-millimetre, so recalibrate after changing either.
- Without calibration the ruler assumes the CSS reference size of 96 pixels per inch, which many real displays do not match, so treat uncalibrated millimetre figures as rough estimates.
- The measuring area is a fixed canvas on this page: it measures boxes you draw here, using known-size test elements, not arbitrary windows elsewhere on your screen.
The two screens pack pixels at different densities, and display scaling differs too. Pixels are the same count on both; the physical size differs. Calibrate on each screen for accurate millimetres.
About this tool
The Screen Ruler and Pixel Measure lets you measure anything you can draw a box around on screen: drag on the measuring area and read the box's width, height and diagonal in pixels. With a quick calibration using a bank card, it also estimates the size in millimetres and centimetres. Designers use it to sanity-check layouts and spacing without opening a graphics editor.
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Part of Ovatly's free tools in Productivity Tools.