Area of a Rectangle Calculator
Calculate the area, perimeter, and diagonal of a rectangle from its length and width. See also Area of Parallelogram Calculator and Area of Trapezoid Calculator.
How to Calculate the Area of a Rectangle
To find the area of a rectangle, multiply its length by its width. The length is the longer side and the width is the shorter side, though the formula works regardless of which you call which. The result is in square units. You can also find the perimeter (total distance around) by adding all four sides: P = 2(l + w), and the diagonal using the Pythagorean theorem: d = √(l² + w²).
Rectangle Area Formula
Area = length × width
Perimeter = 2 × (length + width)
Diagonal = √(length² + width²)
Example
Find the area of a rectangle with length 10 and width 6:
A = length × width
A = 10 × 6
A = 60 square units
Perimeter = 2 × (10 + 6) = 32
Diagonal = √(100 + 36) = √136 ≈ 11.6619
Rectangle Area Reference Table
| Length | Width | Area | Perimeter | Diagonal |
|---|---|---|---|---|
| 2 | 1 | 2 | 6 | 2.2361 |
| 4 | 3 | 12 | 14 | 5.0000 |
| 5 | 3 | 15 | 16 | 5.8310 |
| 6 | 4 | 24 | 20 | 7.2111 |
| 8 | 5 | 40 | 26 | 9.4340 |
| 10 | 6 | 60 | 32 | 11.6619 |
| 12 | 8 | 96 | 40 | 14.4222 |
| 15 | 10 | 150 | 50 | 18.0278 |
| 20 | 12 | 240 | 64 | 23.3238 |
| 25 | 15 | 375 | 80 | 29.1548 |
| 50 | 30 | 1500 | 160 | 58.3095 |
| 100 | 50 | 5000 | 300 | 111.8034 |
Frequently Asked Questions
What is the difference between area and perimeter?
Area measures the space inside the rectangle (in square units), while perimeter measures the total distance around the outside (in linear units). Area = l × w, Perimeter = 2(l + w).
Is a square a special rectangle?
Yes. A square is a rectangle where all four sides are equal. The area formula still applies: A = side × side = side².
How do I find the diagonal of a rectangle?
Use the Pythagorean theorem: diagonal = √(length² + width²). The diagonal divides the rectangle into two right triangles.
Can I find the area if I only know the perimeter?
Not uniquely — many rectangles can share the same perimeter but have different areas. You need both length and width, or the perimeter plus one side length.