How to use the online protractor
This full-circle protractor has a fixed baseline pointing left at 0°. Rotate only the measuring arm or enter a value from 0° to 360°. The top is 90°, right is 180° and bottom is 270°. Angles do not depend on your display’s centimeter calibration.
Use the online protractor
Place the center at the vertex and align the fixed left baseline with one side. Rotate the single handle to align the measuring arm with the other side. Left is 0°, top is 90°, right is 180° and bottom is 270°. Angles increase from the left through the top toward the right. You can also enter 270° or 360° directly.
From acute angles to a full turn
An acute angle lies between 0° and 90°, a right angle is 90°, and an obtuse angle lies between 90° and 180°. A straight angle is 180°. A reflex angle is greater than 180° and less than 360°. The opposite-direction angle equals 360° minus the current reading.
Get a better alignment
View the screen straight on to reduce visual alignment errors. Focus a handle with Tab and use the arrow keys for fine adjustments. This tool does not upload images or correct camera perspective; angles in a distorted photograph require an appropriate undistorted reference.
A few common questions
Do I need screen calibration for angles?
On an ordinarily scaled display, an angle is independent of physical size. You do not need centimeter calibration to measure it.
Can I measure a full 360-degree angle?
Yes. The circular scale supports 0° to 360°. Coincident arms normally represent 0°; enter 360 to explicitly display one full turn.