Rectangle Calculator

Calculate the area, perimeter, and diagonal of a rectangle instantly.

Rectangle Calculator

Enter the length and width of the rectangle below to calculate the area, perimeter, and diagonal.

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About This Tool

Welcome to our free online Rectangle Calculator. Whether you're a student working on geometry homework, a carpenter measuring materials, or just someone curious about shapes, this tool is designed to provide instant and accurate calculations.

We built this tool to eliminate the need for manual calculations, offering a simple and intuitive interface to find a rectangle's area, perimeter, and diagonal length all at once just by entering two numbers.

Formulas Used

For a rectangle with length l and width w:

  • Area: Area = l × w
  • Perimeter: Perimeter = 2l + 2w
  • Diagonal: Diagonal = √(l² + w²)

Frequently Asked Questions

What is a rectangle?

A rectangle is a 2D geometric shape with four sides and four right angles (90 degrees). Opposite sides are equal in length and parallel to each other.

What is the difference between length and width?

Conventionally, the longer side is referred to as the length, and the shorter side is the width. However, mathematically, it does not matter which is which for calculating area, perimeter, or diagonal.

Is a square a rectangle?

Yes! A square is a special type of rectangle where all four sides are equal in length. All squares are rectangles, but not all rectangles are squares.

How do you find the area of a rectangle?

You find the area by multiplying the length by the width. The formula is Area = length × width, and the result is typically expressed in square units.

What is the perimeter of a rectangle?

The perimeter is the total length of the outside boundary of the rectangle. You can calculate it by adding all four sides together, or by using the formula Perimeter = 2 × (length + width).

How do you calculate the diagonal of a rectangle?

The diagonal is the straight line connecting opposite corners of the rectangle. You calculate it using the Pythagorean theorem: Diagonal = √(length² + width²).

Can a rectangle have a length or width of zero?

In physical geometry, a rectangle must have positive length and width to exist as a 2D shape. If either dimension is zero, it essentially becomes a line segment or a point.

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