Geometry
Rectangle area & perimeter
- where
- area (m²)
- length (m)
- width (m)
- perimeter (m)
Explain this equation
This gives the area and perimeter of a rectangle, such as a slab, a base, a panel or the plan of a building. Area is used for quantities; perimeter is used for footings, edging, DPC runs and setting-out.
L and W are the two side lengths in metres. A is the space enclosed, in m². P is the distance all the way round the outside, in m.
Area is length times width. The perimeter has two lengths and two widths, so it is 2(L + W).
A 4 m × 3 m base is 12 m² and has a 14 m perimeter. Doubling both sides multiplies the area by four but only doubles the perimeter, which is why larger plans have proportionally less edge.
Watch out: decide which line you are measuring. Outside faces, centrelines and inside faces give different perimeters on a real wall.
Calculate a rectangular plan, base or panel.
Enter your values to see the result.
Good to know
Perimeter is the complete outside boundary.
Sources
- Geometry / arithmetic
Estimates are not design approval or British Standards compliance checks. Structural arch, retaining-wall, wind, foundation, lintel and masonry-capacity design are not performed. Use the project engineer’s specification.