Rectangle Area Calculator

Formula

A = b × h

Area of a rectangle: formula and worked example

A rectangle is a four-sided shape with four right angles, where each pair of opposite sides has the same length. To get the area you multiply base by height: A = b·h. Take b = 6 m and h = 4 m and the area comes to 24 m². The perimeter is P = 2(b + h), and for the diagonal you lean on Pythagoras: d = √(b² + h²). Same example, d = √(36 + 16) = √52 ≈ 7.21 m.

Where the rectangle shows up in practice

Floors, walls, screens, doors, windows, and almost every paper size you handle. When you are painting or tiling a wall, tack on a 10% safety margin for cuts and waste. Paper is a neat case: the A-series (A0, A1, …, A4) keeps a fixed ratio of √2 between its sides. Fold an A4 in half and you get an A5 with exactly the same proportions, which is why layouts and margins scale so cleanly from one size to the next.

Then there is the golden rectangle, prized for its looks, with sides in the ratio b/h = φ ≈ 1.618 (the golden ratio). You meet it again and again in classical architecture (the Parthenon facade), in Renaissance painting and in modern logo work. Its quirk: slice off a square and what remains is a smaller golden rectangle, a shape that keeps repeating itself.