Online Protractor

Drag the arms to measure any angle from 0° to 180°. The reading shows degrees, the supplementary and reflex angles, and radians.

How to read a protractor

A protractor has two scales. Use the outer scale when your angle opens from the right (0° on the right) and the inner scale when it opens from the left. Line the center point up with the corner (vertex) of the angle and one side with 0°.

Types of angles

• Acute: less than 90°
• Right: exactly 90°
• Obtuse: between 90° and 180°
• Straight: 180°
• Reflex: more than 180°

Need one on paper? Print our printable protractor.

FAQ

How do I use the online protractor?

Drag the two arms to line up with the angle you want to measure. The angle between them appears instantly, along with its supplement and reflex angle. Hold Shift to snap to whole degrees.

Can I measure an angle in a photo?

Yes. Open the photo on the same screen next to this page, or take a screenshot and hold your phone up to the screen. The protractor doesn't need calibration because angles don't depend on screen size.

How do I measure an angle larger than 180°?

Measure the smaller angle and read the reflex value: 360° minus the measured angle.

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