Regular Polygon Calculator
Calculate angles, area, and perimeter of any regular polygon from a triangle to a dodecagon
About this calculator
The Regular Polygon Calculator computes interior angles, exterior angles, area, perimeter, and apothem for any regular polygon from a triangle to a 20-sided figure. Enter the number of sides and side length to instantly see all properties. Great for geometry, architecture, and understanding how polygons scale.
How to use the Regular Polygon Calculator calculator
- Enter the measurements you know into the input fields.
- Read the computed properties — they update instantly as you type.
- Compare the diagram with your figure to confirm the setup is right.
- Copy the page URL to share the exact calculation.
Common examples
- Equilateral triangle (3 sides), side = 6 cm → Area ≈ 15.59 cm², Perimeter = 18 cm, Interior angle = 60°
- Square (4 sides), side = 5 m → Area = 25 m², Perimeter = 20 m, Interior angle = 90°
- Regular pentagon (5 sides), side = 4 cm → Area ≈ 27.53 cm², Perimeter = 20 cm, Interior angle = 108°
- Regular hexagon (6 sides), side = 3 cm → Area ≈ 23.38 cm², Perimeter = 18 cm, Interior angle = 120°
- Regular octagon (8 sides), side = 2 m → Area ≈ 19.31 m², Perimeter = 16 m, Interior angle = 135°
Frequently asked questions
How does the Regular Polygon Calculator calculator work?
Enter the known measurements of your figure and the calculator applies the standard geometric formulas to find the remaining properties, alongside a diagram that reflects your numbers. All values are computed with high-precision arithmetic.
When would I use the Regular Polygon Calculator calculator?
It helps with geometry homework, technical drawing, construction and DIY layout, and any situation where you know some measurements of a shape and need the rest.
How accurate are the results?
Formulas are evaluated at 30 significant digits of precision internally, including roots and trigonometric functions. Displayed values are rounded for readability, but the underlying computation does not accumulate floating-point drift.
Can I share a specific calculation with someone else?
Yes. Every value you enter updates the URL, so copying the address bar and sharing the link reopens the exact same figure and results for whoever clicks it.