How many acute angles can be in a quadrilateral?

A quadrilateral can have 0 to 3 acute angles, but never 4:

• A rectangle and a square are both quadrilaterals with four right angles, hence they have no acute angles.
• A kite-shaped figure can have one acute and three obtuse angles, or three acute and one obtuse angles.
• A parallelogram and a rhombus have two acute and two obtuse angles.

The sum of the interior angles of any quadrilateral is 360º; thus it would be impossible for all angles to be acute (less than 90º each)