Capture
Click Start screen capture and choose a screen, window, or tab. Pick Entire screen to measure outside the browser.
Measure angles and distances
anywhere on your screen
Including content outside the browser. Capture your screen, then click to measure. Everything stays on your device.
Click Start screen capture, then choose a screen or window to share. Pick a whole monitor to measure things outside the browser.
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Click two points a known distance apart.
Enter the real distance between the two points:
Tap to place points. Drag empty space to pan, scroll to zoom, drag a handle to fine tune.
How to use
Zoom in
Freeze the frame, then scroll or use +/− to zoom and drag to pan. Full screen gives the most room for precise clicks.
Angle
In Angle mode, click three points: one arm, the vertex, then the other arm. The reflex angle is shown too.
Distance & scale
Distance mode measures between two points. Use Scale to calibrate from a known length and read real units.
Everything runs locally in your browser. The screen stream is never uploaded.
A screen ruler and protractor that works anywhere
Screen Ruler is a free online tool for measuring angles and distances directly on your screen. Because it uses your browser's screen-capture feature, you can measure on top of any application - a CAD drawing, a PDF, a photo, a map, a game, or a design mockup - not just web pages. Share a single window or your entire monitor, freeze the frame, zoom in, and click to measure with precision.
Use Angle mode as an on-screen protractor: click the two arms and the vertex to read the angle in degrees, including the reflex angle. Use Distance mode as a pixel ruler, or calibrate a real-world scale from a known length to read millimetres, centimetres, metres, inches, or feet. Nothing is installed and nothing is uploaded - the capture is processed entirely on your device.
Frequently asked questions
How do I measure an angle on my screen?
Click Start screen capture and share your screen, then in Angle mode click three points: one arm, the vertex, then the other arm. The angle in degrees appears instantly.
Can I measure things outside the browser?
Yes. Choose Entire screen when sharing and you can measure angles and distances on any application or window on that monitor, not just the browser.
How do I measure a real-world distance?
Use Configure scale: click two points a known distance apart and enter that distance and unit. Distance mode then reports measurements in real units.
Is Screen Ruler free and private?
Yes. It is free and runs entirely in your browser. The captured screen is processed locally and never uploaded.
Which browsers are supported?
Recent Chrome, Edge, and Firefox support the Screen Capture API used here. Safari support is more limited.