Understanding Rectangle Measurements
A rectangle has four sides with opposite sides equal in length and four 90° corners. Knowing the length and width is enough to calculate several other useful measurements, including area, perimeter, and the distance diagonally from one corner to the opposite corner.
Rectangle calculations are useful for everything from measuring rooms and walls to sizing panels, sheets, workpieces, gardens, and other rectangular spaces.
Area vs. Perimeter
Area measures the amount of surface contained inside a rectangle. It is calculated by multiplying the length by the width and is expressed in square units, such as square feet, square inches, or square meters.
Perimeter measures the total distance around the outside edge. It is calculated by adding all four sides, or by multiplying the sum of the length and width by two. Because perimeter measures distance rather than surface area, it is expressed in regular linear units rather than square units.
Using the Diagonal Measurement
The diagonal is the straight-line distance from one corner of a rectangle to the opposite corner. This measurement can be useful when checking whether a rectangular layout is square.
For construction or layout work, measuring both diagonals provides a useful check. If the opposite sides are positioned correctly and both diagonal measurements are equal, the corners should form a square rectangular layout.
Why Aspect Ratio Can Be Useful
Aspect ratio compares a rectangle's length with its width. Two rectangles can have completely different physical sizes while still having the same aspect ratio.
Aspect ratios are commonly used for screens, photographs, signs, panels, layouts, and other applications where the proportions of a rectangle matter in addition to its actual dimensions.
Common Uses for Rectangle Calculations
Rectangle measurements are useful when estimating flooring, carpet, tile, drywall, paint coverage, countertops, plywood, sheet metal, fabric, concrete slabs, decking, and other materials. They can also help with room layouts, garden planning, framing, and checking the dimensions of rectangular objects or work areas.