Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Calculate a rectangle's area and perimeter from its length and width.
This tool calculates both the area and perimeter of a rectangle from its length and width.
Enter the length and width. Area and perimeter appear instantly.
Area = length × width
Perimeter = 2 × (length + width)
These two results measure different things, and people often mix them up. The area is the amount of flat surface inside the rectangle, measured in square units. The perimeter is the total distance around the outside edge, measured in ordinary length units. You need the area when you are covering a surface, for example with flooring, paint, sod, or fabric. You need the perimeter when you are running something along the edge, such as fencing, baseboards, a border, or a picture frame. The calculator shows both to four decimal places, using whatever unit you enter.
Imagine a hypothetical rectangular room that is 4.5 meters long and 3.2 meters wide. Enter length 4.5 and width 3.2.
Area = 4.5 × 3.2 = 14.4 square meters
Perimeter = 2 × (4.5 + 3.2) = 15.4 meters
If you were laying flooring, the surface to cover is 14.4 square meters, and you would normally order extra to allow for cuts and waste. If you were fitting skirting boards, you would start with 15.4 meters, then subtract door openings and add spare length for angled cuts.
A perimeter of 40 units could be a 10 by 10 square with an area of 100, a 15 by 5 rectangle with an area of 75, or a 19 by 1 strip with an area of only 19. For a fixed perimeter, the area is largest when the rectangle is a square and shrinks as it becomes long and thin. This matters when you are planning a fenced garden or pen with a limited amount of fencing: making the shape closer to square gives the most enclosed space. You can test this yourself by trying different length and width pairs whose sum stays the same.
If you know the area and one side, the other side is the area divided by the known side. A hypothetical 60 square meter rectangle that is 12 meters long must be 5 meters wide. If you know the perimeter and one side, the other side is half the perimeter minus the known side. Enter the recovered pair to confirm the tool returns the values you started with.
That's a square -- see the dedicated Square Area & Perimeter Calculator.
No. Multiplication and addition do not depend on order, so swapping them gives the same area and perimeter.
This tool does not calculate it, but you can use the Pythagorean theorem: the diagonal is the square root of length squared plus width squared. For a 3 by 4 rectangle it is 5.
Split it into two rectangles, run each one through the calculator, and add the areas. For the perimeter of the whole outline, add up every outer edge instead of adding the two separate perimeters.
That depends on the material and the cutting pattern, so follow the manufacturer or supplier advice. The calculator gives only the exact geometric area.
Reference: NIST Weights and Measures