What is it?
The Online Protractor measures any angle: on the screen, or in a photo you open, like a roof slope, a ramp, a posture or a homework diagram.
Who is it for?
Students with geometry homework, carpenters and builders checking angles in photos, physiotherapy and posture checks, and designers.
How to measure
- Drag the pink corner onto the point of the angle, then drag the two blue dots along each side of it. (The tool shows this hint too.)
- Read the Angle; the other side of the angle is shown too, so 120° also shows (other side 240°).
- Reset handles starts again.
Angles in a photo
- Tap Measure an angle in a photo and choose the picture.
- Place the handles on the lines in the photo. Remove photo clears it.
The photo never leaves your device.
Accurate photo angles
- Take the photo straight on, with the camera square to the surface. Photos taken from an angle distort angles.
- Wide-angle lenses bend lines near the edges. Keep the object in the middle of the photo.
- Zoom the page to place the handles precisely on small details.
For slopes on site, a phone’s spirit level or a real inclinometer is better than a photo.
Example
To check a ramp in a photo, place the corner where the ramp meets the ground and the dots along the ground and the ramp: an angle near 5° meets common accessibility ramp guidance.
Errors and how to fix them
- Photo won’t open: use JPG or PNG.
- Handles hard to place: zoom the page and use Reset handles to start again.
Open the tool: Online Protractor
Still stuck?
Contact support. Tell us which tool or page you were using, what you tapped, what you saw, and your phone or computer and browser (for example: Android phone, Chrome). We reply by email.
Questions, or an error not listed here?
Tell us in the comments: what you were doing, the exact message you saw, and your device and browser. We read every comment and add new fixes to this article.