⬡ Regular Polygon Calculator
Calculate the area, perimeter, interior angle, apothem, and circumradius of any regular polygon.
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What this calculator finds
A regular polygon has all sides and all interior angles equal. Given the number of sides and the length of one side, this calculator finds the shape’s area, perimeter, interior angle, apothem (distance from center to the midpoint of a side), and circumradius (distance from center to a vertex).
The formulas
- Area = (n · s²) / (4 · tan(π/n))
- Perimeter = n · s
- Interior angle = (n − 2) · 180° / n
- Apothem = s / (2 · tan(π/n))
- Circumradius = s / (2 · sin(π/n))
where n is the number of sides and s is the side length. As n grows large, a regular polygon’s shape approaches a circle. This tool is for general math and educational purposes.
Last reviewed August 2026