Area and perimeter of shapes
Rectangles, triangles, circles, trapezoids, ellipses and regular polygons.
Tool
Tools › Geometry and measurement
How it is calculated
Rectangle: area = length × width. Triangle: area = base × height ÷ 2. Trapezoid: area = (longer base + shorter base) × height ÷ 2.
Circle: area = π × diameter² ÷ 4 and perimeter = π × diameter, with π ≈ 3.1416. A circle 10 m across has 78.54 m² and a circumference of 31.42 m.
Ellipse: area = π × a × b, where a and b are half the length and half the width. The perimeter has no simple exact formula; Ramanujan's approximation is used.
Regular polygon with n sides of length L: area = n × L² ÷ (4 × tan(180°/n)). A hexagon with 2 m sides has 10.39 m².
Keep in mind
- For an irregular plot, split it into triangles, measure their three sides with a string and add the areas with the “Triangle from three sides” tool: there is no need to measure angles or heights.
- Output units are the input units squared: if you measure in paces or varas, the area comes out in square paces or square varas.