Perimeter of a Parallelogram
Total length around a parallelogram.
Formula
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Example
Sides 5 and 8: P = 2(5+8) = 26 units.
How it works
A parallelogram has two pairs of equal opposite sides, so its boundary is made from two copies of one side length and two copies of the adjacent side length. Adding all four sides gives a + b + a + b, which simplifies to 2(a + b). This is why the perimeter depends only on the two adjacent side lengths.
When to use it
Use this formula when you need the distance around a parallelogram-shaped figure, such as in geometry problems, fencing a slanted plot, or finding the border length of a tilted design. It is useful whenever the only side measurements given are the lengths of two adjacent sides.
Worked example, step by step
Suppose a parallelogram has adjacent sides of 6 cm and 11 cm. P = 2(a + b) P = 2(6 + 11) P = 2(17) P = 34 cm
Common mistakes to avoid
- Adding only one pair of equal sides instead of all four sides
- Using the formula with a base and height, which are not the side lengths
- Forgetting to multiply the sum of the adjacent sides by 2
Did You Know?
Opposite sides of a parallelogram are equal, so its perimeter is just twice the sum of two adjacent sides.
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