Polygon angle calculator
Interior, exterior and missing angles
Add a side length to get the size too. Any unit.
Result
Interior angle
120.00°
- Exterior angle
- 60.00°
- Central angle
- 60.00°
- Sum of the interior angles
- 720°
- Diagonals
- 9
Polygon angle calculator
Find the interior, exterior and central angles of any regular polygon, work out how many sides an angle implies, or find the missing angle of any polygon — with area and radii from a side length.
Frequently asked questions
What are the angles of a pentagon?
Each interior angle of a regular pentagon is 108°, and the five interior angles add up to 540°. Each exterior angle is 72°.
The interior angles of any pentagon, regular or not, add up to 540°, and the calculator above finds a missing one. To build a five-sided frame, cut both ends of every piece at 36°: see the miter settings for five sides.
What are the angles of a hexagon?
Each interior angle of a regular hexagon is 120°, and the six interior angles add up to 720°. Each exterior angle is 60°.
These come from a formula that works for any polygon with n sides: the interior angles add up to (n − 2) × 180°, so in a regular polygon each one is (n − 2) × 180° ÷ n. A hexagonal frame is cut at 30° on each end: see the miter settings for six sides.
What are the angles of an octagon?
Each interior angle of a regular octagon, such as a stop sign, is 135°, and the eight interior angles add up to 1,080°. Each exterior angle is 45°.
An eight-sided frame or box is cut at 22.5° on each end: see the miter settings for eight sides. For any other number of sides, change the number above.
Guides
About these measurements
Readings are estimates taken from rendered pixels and consumer device sensors. Do not rely on them for structural engineering, surveying, manufacturing inspection, navigation, or medical decisions. Check anything safety-critical with a calibrated instrument.
All processing happens in your browser. No image, camera frame or sensor reading is ever uploaded.
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