What Is the Perimeter of a Rectangle?
The perimeter of a rectangle is the total distance around its outside edge — the sum of all four sides. Because a rectangle has two pairs of equal sides (two lengths and two widths), you can find the perimeter quickly with a simple formula instead of adding each side individually. This calculator works with any consistent unit (meters, feet, inches, centimeters) and also reports the area as a bonus.
How to Use This Calculator
Enter the length and width of your rectangle in the same unit of measurement, then read off the perimeter. The result table also shows the area (length \(\times\) width) so you have both key measurements in one place. Use whole numbers or decimals — both work.
The Formula Explained
The perimeter formula is $$P = 2 \times \left( \text{Length} + \text{Width} \right)$$ You add the length and the width together to get the measurement of two adjacent sides, then multiply by 2 because the opposite sides are identical. This is mathematically the same as length + length + width + width, just written more compactly.
Worked Example
Suppose a rectangle has a length of 10 m and a width of 5 m. Add them: \(10 + 5 = 15\). Multiply by 2: $$2 \times 15 = 30 \text{ m}$$ The area would be \(10 \times 5 = 50\) square meters. So this rectangle has a perimeter of 30 m and an area of 50 m².
FAQ
What units does the answer use? The perimeter is in the same linear unit you entered (e.g. meters in, meters out). The area is in those units squared.
Does this work for a square? Yes — a square is a special rectangle. Just enter the same value for length and width and the formula still applies.
What if I only know the area and one side? Divide the area by the known side to find the other side, then use the perimeter formula.
