Online Screen Ruler
A pixel-accurate screen ruler you can drag to measure anything on your screen. Shows size in pixels, centimeters, and inches. Calibrate to your monitor.
Screen DPI (96 = standard)
Drag the ruler or its edges to resize
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Pixels
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Centimetres
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Inches
Frequently asked
questions
The pixel measurements are exact. Physical measurements (cm/inches) depend on your screen's DPI (dots per inch). Use the calibration feature — hold a ruler to your screen and drag until it matches — for accurate physical measurements.
Hold a physical ruler against your screen. Use the DPI input field to enter your screen's DPI, or adjust it until the on-screen ruler matches your physical ruler at a known measurement. Standard monitors are 72–96 DPI; modern HiDPI/Retina screens are 144–220+ DPI.
Yes — click the "Vertical" button to switch the ruler orientation. The same drag-to-resize functionality applies.