Angle type
Acute Angle — Less Than 90°
An acute angle is any angle with a measure greater than 0° and less than 90°. Think “sharp” — like the point of a slice of pizza.
Updated Online Protractor
Range: 0° < acute < 90° (0 < rad < π/2).
Examples: 15°, 30°, 45°, 60°, 75°.
Acute angles appear everywhere — triangle corners, roof pitches, clock hands at 1:05, and the hands of scissors when slightly open.
On the tool: snap to 30°/45°/60° or set snap “Off” for 45.2°-style readings.
How to measure an acute angle
- Place the protractor center on the vertex.
- Align handle A with one edge at 0° (usually the left-to-right baseline).
- Drag handle B to the second edge — a reading like
45.0°with label Acute confirms it.
If the reading jumps to 315° instead of 45°, you’re seeing the reflex complement — toggle “Measure reflex angle” off to see the inner acute value.