Perimeter is the measurement obtained as a result of the sum of the sides of a flat geometric figure. That is, the perimeter is what the contour of the figure measures.

The term perimeter comes from the Greek *περίμετρος* , a word made up of the prefix *περί* (peri), which means around and *μετρος* (metron), which means measure.

Perimeter is also a word used in military jargon to refer to a high security space.

## How to remove the perimeter

To calculate the perimeter of a geometric figure it is necessary to know two basic variables:

- The number of sides of the figure.
- The length of each of those sides.

In the case of the circumference, it is necessary to know the length of the radius or the diameter of the circumference in order to calculate its perimeter.

## Perimeter formulas

These are the formulas to calculate the perimeter of some basic geometric figures:

### Scalene triangle

A scalene triangle is one that has three unequal sides. The **formula to calculate the perimeter of a scalene triangle** is:

*P = a + b + c*

*where a, b and c are each of the sides.*

An **example of perimeter in a scalene triangle** whose sides measure 3, 4 and 12 cm, would be:

P = 3 + 4 + 12

P = 19 cm.

See also Scalene triangle.

### Isosceles triangle

An isosceles triangle is one that has two equal sides. The **formula to calculate the perimeter of an isosceles triangle** in this case, would be:

*P = 2xl + b*

An **example of perimeter in an isosceles triangle** , whose sides measure 37, 37, and 15 cm, would be:

P = 2×37 + 15

P = 74 + 15

P = 89 cm.

### Equilateral triangle

The equilateral triangle is one that has three equal sides. The **formula for the perimeter of the equilateral triangle** is:

*P = 3xl*

An **example of perimeter in an equilateral triangle** whose sides measure 9 cm would be:

P = 3×9

P = 27 cm.

### Square

A square is a flat geometric figure that has four equal sides. The **formula to calculate the perimeter of a square** is:

*P = 4xl*

An **example of perimeter in a square** whose sides measure 7.5 cm would be:

P = 4×7.5 cm.

P = 30 cm.

### Rectangle

A rectangle is a flat geometric figure that has four sides with two different measurements (height and width). The **formula to calculate the perimeter of a rectangle** is:

*P = 2x (a + b)*

An **example of perimeter in a rectangle** whose sides measure 2 and 8 cm respectively, would be:

P = 2x (2 + 8)

P = 2x (10)

P = 20 cm.

### Circumference

A circumference is a closed, flat, curved line formed by points that are equidistant from the center.The **formula for the circumference of the circumference** is:

*P = 2π. r*

An **example of the perimeter of a circle** whose radius measures 7.47 cm would be:

P = 2x (3.14) x 7.47

P = 6.28x 7.47

P = 46.91 cm.