Rectangle Area Calculator
Calculate the area, perimeter, and diagonal of a rectangle from its length and width.
Enter the length and width of the rectangle
Area
—
Perimeter
—
Diagonal
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Rectangle Formulas
Area = length × width
Perimeter = 2 × (length + width)
Diagonal = √(length² + width²)
Perimeter = 2 × (length + width)
Diagonal = √(length² + width²)
Example: A rectangle with length 8 and width 5
Area = 8 × 5 = 40 square units
Perimeter = 2 × (8 + 5) = 26 units
Diagonal = √(64 + 25) = √89 ≈ 9.434 units
Area = 8 × 5 = 40 square units
Perimeter = 2 × (8 + 5) = 26 units
Diagonal = √(64 + 25) = √89 ≈ 9.434 units
Special Cases
| Shape | Condition |
|---|---|
| Square | length = width |
| Golden Rectangle | length / width ≈ 1.618 |
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 edge (in linear units).
How is the diagonal calculated?
The diagonal of a rectangle is found using the Pythagorean theorem. Since the diagonal creates a right triangle with the length and width, d = √(l² + w²).
Can a rectangle have equal length and width?
Yes — a rectangle with equal sides is called a square. A square is a special case of a rectangle.
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Last updated: 2026-08-08