Rectangle Calculator
Find area, perimeter, and diagonal of a rectangle
Results
Area
Perimeter
Diagonal
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Rectangle Calculator Formula
Area of a rectangle:
A = length × width
Perimeter of a rectangle:
P = 2 × (length + width)
Diagonal of a rectangle:
d = √(length² + width²)
How to Use This Calculator
- Enter the length of the rectangle.
- Enter the width of the rectangle.
- Click Calculate to see area, perimeter, and diagonal.
- Share your result by copying the URL that updates automatically after calculating.
Frequently Asked Questions
What is the formula for the area of a rectangle?
The area of a rectangle is A = length × width. This equals the number of unit squares that fit inside the shape. For example, a rectangle 10 meters long and 5 meters wide has an area of 50 square meters.
How do you find the perimeter of a rectangle?
The perimeter is the total distance around the outside: P = 2 × (length + width). Unlike area, perimeter is measured in linear units (meters, feet), not square units.
What is the diagonal of a rectangle?
The diagonal connects two opposite corners and is calculated using the Pythagorean theorem: d = √(length² + width²). If you need to calculate angles of the diagonal, use the Pythagorean theorem calculator.
What units are used?
This calculator is unit-agnostic. If you enter measurements in feet, area is in square feet, perimeter in feet, and diagonal in feet. Just be consistent with your units. To convert area units, use the area converter.
Is a square a rectangle?
Yes. A square is a special rectangle where all four sides are equal. The area formula A = length × width still applies — for a square, it becomes A = s². Similarly, the diagonal of a square simplifies to d = s × √2.
Can I share my calculation?
Yes. After clicking Calculate, the URL updates with your length and width values. Copy and share the URL to let anyone open the same pre-filled form with all three results.