How to Calculate the Width of a Rectangle With the Perimeter

A rectangle is a two-dimensional geometric shape composed of two sets of parallel lines that intersect at right angles. Each side of a rectangle, its length or width, has a side opposite of equal length and adjacent sides of differing lengths. The perimeter of any geometric object is the distance around that object, and the perimeter of a rectangle is the sum of its sides' measurements. The width of a rectangle can be calculated from its perimeter and length.

Instructions

Perimeter and Length

1. Double the length of the rectangle. For example, the length is 21. Multiplying 21 by 2 results in 42.

2. Subtract the doubled length from the perimeter. For this example, the perimeter is 70. Subtracting 42 from 70 results in 28.

3. Divide the difference of the perimeter and the length doubled by 2. For this example, 28 divided by 2 equals 14. The width of the rectangle is 14.

References

• AAA Know: Perimeter of a Rectangle
• Math Goodies: Perimeter
• Math Is Fun: Quadrilaterals

Resources

• Calculator Soup: Rectangle Calculator