Formula and example
How it is calculated
A = ½·|Σ(xᵢ·yᵢ₊₁ − xᵢ₊₁·yᵢ)|. The perimeter is the sum of distances between consecutive vertices.
Worked example
The points (0;0), (4;0), (4;3), (0;3) give an area of 12 cm², a perimeter of 14 cm and a centroid at (2;1.5).
Things to check
- Enter the points in order around the boundary. Non-adjacent edges that cross or touch are rejected.
- Holes and geographical coordinates on a sphere are not modelled. The centroid assumes a uniformly filled area.
Frequently asked questions
Do I need to repeat the first point at the end?
No. The final edge back to the first point is added automatically. An exactly repeated closing coordinate is also accepted.