An acute angle is less than 90°. An obtuse angle is between 90° and 180°. A reflex angle is between 180° and 360°. The size of an angle can be estimated without using a protractor.

This KS2 maths article explores how an angle is a measure of a turn. Learn how to draw and measure angles using a protractor.

In this video from DIY YouTuber See Jane Drill, we learn how to measure the angle of the necessary cut with nothing but a decent level.