Geometry
Rectangle area & perimeter
- where
- area (m²)
- length (m)
- width (m)
- perimeter (m)
Explain this equation
Works out the area and perimeter of any rectangle: a floor, a ceiling, a base, a panel or a wall elevation. Use area for boards, sheets and finishes, and perimeter for trims, edging or a run of formwork.
L and W are the two side lengths in metres. A is the surface they enclose in square metres. P is the distance all the way round the outside edge, in metres.
A rectangle is L strips of width W laid side by side, so the area is simply L × W. The boundary has two lengths and two widths, which is why P = 2(L + W).
A 4 m × 3 m room is 12 m² with a 14 m perimeter. Double one side and the area doubles, but the perimeter grows by only twice that side.
Watch out: measure both sides in metres. Mixing millimetres and metres gives an area that is out by a factor of a thousand.
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
This is a calculation aid, not a structural design or compliance certificate. Every default is an example, not a specification for your project.