Online Protractor
Drag the arms to read any angle, type an exact one, or put a photo behind it: 360°, free.
or measure over a photo · see all measuring tools
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Drag the arms · the round handle rotates, tap it to reset · pinch to zoom
Drag the arms to read any angle, type an exact one, or put a photo behind it: 360°, free.
or measure over a photo · see all measuring tools
This is a real protractor on your screen: a 180° or 360° instrument with two draggable arms and a live readout in degrees. Drag either arm and the angle between them updates instantly, along with its complementary and supplementary partners and the value in radians. If you already know the angle you need, type it into the exact-angle box and the arms jump to it - handy for drawing, checking homework answers, or setting a bevel.
Nothing installs and nothing uploads. The protractor is drawn by your browser, so it stays razor sharp at any size - scale it up with a pinch or the mouse wheel and rotate the whole instrument to fit whatever you are measuring.
Press Open protractor and the instrument appears with its two arms at 60°. Drag either arm to any angle and the reading follows in whole degrees; for tenths of a degree, tap the big reading and type the exact value - the arms jump to it. The 180° / 360° switch changes between the half-circle scale and the full circle, where reflex angles read directly without adding two measurements together.
To measure on a photo, press the photo button - or just drop or paste an image anywhere on the page - and the picture slides in behind the instrument. Lower the photo opacity, move and rotate the protractor over the detail you care about, and read the angle. The eye button hides the dial so only the two arms remain over the picture. For measurements that stay drawn on the image - with saved lines you can download - use the angle measurer instead; it is built exactly for that.
A physical object works too: scale the protractor up, press the padlock so touches change nothing, and hold the object flat against the screen - line its edges up with the arms and read the angle. The lock is what makes this work, because the object touching the screen cannot move anything. The same trick measures things already on your display: drop the center on any corner you see and line the arms up with its edges.
The whole measuring family works the same way: distances, areas, perimeters and circle radii on photos, plus pixel coordinates.
Yes, completely - every feature on this page is free, with no account, watermark or daily limit. It runs inside your browser, and a photo you place behind the instrument never leaves your device.
The instrument itself is exact: arms sit at the angle shown to a tenth of a degree, and typed angles are set precisely. When you measure a photo, the practical accuracy depends on the photo - perspective and lens distortion can make a true right angle look like something else in the picture, so shoot as straight-on as you can.
The 180° mode is the classic half-circle school protractor with the double scale, best for geometry class. The 360° mode measures a full turn, so reflex angles - anything past 180° - read directly without adding two measurements together.
Yes, two ways. Put the picture behind this protractor and align the arms by eye, or use the dedicated measure angle tool, where you click three points on the photo and the angle is computed for you and stays drawn on the image.
Two angles are complementary when they add up to 90° and supplementary when they add up to 180°. The tool shows both partners for the current reading automatically - measure 35° and it tells you the complement is 55° and the supplement is 145°.
Yes - the arms are made for fingers and pinch scales the instrument. The padlock freezes it so you can even measure a small object held against the display.