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Polygon Calculator
Find the angles, area, perimeter and diagonals of any regular polygon.
Regular polygon calculator
Area: —
Perimeter: —
Interior angle: —
Exterior angle: —
Apothem: —
Circumradius: —
Diagonals: —
How to use the Polygon Calculator
- Enter how many sides the regular polygon has.
- Enter the length of one side.
- Read the angles, area, perimeter and diagonals.
Features
- Interior and exterior angles
- Area and perimeter from the side length
- Apothem, circumradius and diagonal count
- Runs locally in your browser
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Frequently Asked Questions
Common questions about the free online polygon calculator.
Enter the number of sides and the side length. The tool applies the standard regular polygon
area formula and shows the result.
Each interior angle is n minus two, multiplied by 180 and divided by n, where n is the number
of sides in the polygon.
The exterior angle is 360 divided by the number of sides, and all the exterior angles always
add up to 360 degrees.
A polygon with n sides has n times n minus three, divided by two diagonals, and the tool
works that number out for you.
The apothem is the distance from the centre of the polygon to the midpoint of any side, and
it is used in the area formula.
No. Every calculation happens locally in your browser, so nothing you type is ever sent to a
server.
Yes. The calculator is fully responsive and works on desktop, tablet and phone screens of any
size.
Yes. The polygon calculator is completely free, unlimited and needs no account, sign-up or
installation.
Last updated: October 10, 2026