The square footage of a regular pentagon is about 1.720 × side². Measure one side in feet, square it, and multiply by 1.720. For example, 6-foot sides cover 1.720 × 6² ≈ 61.9 square feet.
For decks and floors, see our octagon deck guide and square footage calculator for polygon area in practice.
How to Calculate the Square Footage of a Regular Pentagon
A regular pentagon has five equal sides, so one side length is enough. Pentagons are used for gazebos, corner garden beds and some decorative patios and window bays.
The formula
Area = ¼ × √(5(5 + 2√5)) × side² ≈ 1.720 × side²
The pentagon is five identical triangles meeting at the centre; the 1.720 factor adds them up.
How to measure
Measure one side from corner to corner, then check a second side. If the sides differ, the shape is irregular — a baseball home plate is a common example — and should be split into a rectangle and a triangle instead.
Worked example
A pentagonal gazebo floor has 7-ft sides.
Area = 1.720 × 7² = 1.720 × 49 ≈ 84.30 square feet. Allow 10–15% extra decking for the angled cuts.
Where this shape is used
- Gazebos: Five-sided gazebo floors and roofs.
- Corner garden beds: Pentagon beds fill a corner with straight edges.
- Feature patios: Pavers and gravel for five-sided seating areas.
Related shape calculators
Working with a different shape? Try the hexagon calculator, heptagon calculator, octagon calculator, or the decagon calculator. Each one shows the formula, a worked example and unit conversions.