Area of Rectangle Calculator
Area
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Perimeter
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Diagonal
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How to Calculate the Area of a Rectangle
The area of a rectangle is calculated by multiplying its length by its width: A = L x W. This is one of the most fundamental formulas in geometry, used in everything from flooring projects to land measurement. The perimeter, or total distance around the rectangle, is P = 2(L + W).
This calculator also computes the diagonal using the Pythagorean theorem: d = sqrt(L² + W²). The diagonal is useful when you need to know the longest straight-line distance across a rectangular space, such as fitting furniture through a doorway or determining screen size.
All measurements are unit-agnostic — enter values in meters, feet, inches, or any consistent unit. The results will be in the corresponding squared units for area, and linear units for perimeter and diagonal.
Frequently Asked Questions
What is the formula for the area of a rectangle?
The area of a rectangle equals length multiplied by width (A = L × W). For example, a rectangle 8 meters long and 5 meters wide has an area of 40 square meters.
How do you find the perimeter of a rectangle?
The perimeter is the sum of all four sides: P = 2(L + W). For a 10 × 6 rectangle, the perimeter is 2(10 + 6) = 32 units.
How is the diagonal of a rectangle calculated?
The diagonal is found using the Pythagorean theorem: d = √(L² + W²). This gives the straight-line distance from one corner to the opposite corner.
Is a square a special type of rectangle?
Yes, a square is a rectangle where all four sides are equal. Every formula for rectangles works for squares — you simply use the same value for both length and width.