Regular polygon interior/exterior angle, perimeter, apothem, area, and circumradius from side count and length.. Regular Polygon Calculator is a free online tool from the ToolsRift Math Calculators collection. It runs entirely in your browser — nothing to install, no signup, and your data never leaves your device.
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How to use Regular Polygon Calculator
Enter the number of sides and the side length and the calculator returns angles, perimeter, apothem, area and circumradius.
Frequently asked questions
How is the interior angle of a regular polygon found?
Interior angle = (n−2) × 180° / n, where n is the number of sides.
What is the apothem?
The distance from the center to the midpoint of a side; it equals s / (2 tan(π/n)) for side length s.
How is the area calculated?
Area = (1/2) × perimeter × apothem, or equivalently (1/4)n·s²·cot(π/n).
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