Rectangle: properties & formulas
Four right angles and two pairs of equal opposite sides make the rectangle a useful model for rooms, screens, and sheets of paper.
- 4 sides
- 4 right angles
- 2 equal diagonals
- 2 lines of symmetry
Properties of a rectangle
| Sides | 4; opposite sides are equal and parallel |
|---|---|
| Vertices | 4 |
| Interior angles | Four 90° angles (sum 360°) |
| Diagonals | 2, equal in length; they bisect each other |
| Lines of symmetry | 2 (4 for a square) |
| Rotational symmetry | Order 2 (order 4 for a square) |
Rectangle formulas
| Area | A = wh |
|---|---|
| Perimeter | P = 2(w + h) |
| Diagonal | d = √(w² + h²) |
| Missing side | w = A / h |
Rectangle area calculator
Give your shape a size.
Use the same unit for every dimension. Changing the unit relabels the measurements; it does not convert them.
From dimensions to an answer
A worked example
An 8 × 5 rectangle has area 40 square units, perimeter 26 units, and diagonal √89 ≈ 9.434 units.
Rectangle: common questions
Wondering about the why? Start here.
How do I find a rectangle’s dimensions from its area and perimeter?
The width and height are the two numbers whose product is the area and whose sum is half the perimeter. For area 24 and perimeter 20, look for two numbers that multiply to 24 and add to 10: the rectangle is 6 × 4.
How do I calculate a rectangle’s area and perimeter?
Multiply width by height for area: A = wh. Add width and height and double the result for perimeter: P = 2(w + h). A 6 cm by 4 cm rectangle has area 24 cm² and perimeter 20 cm.
Compare area and perimeterIs a square also a rectangle?
Yes. A rectangle has four right angles, and a square satisfies that definition with all four sides equal. Enter the same width and height to calculate a square’s area and perimeter.
Explore regular polygons