# What is the perimeter?

Perimeter is one of mathematical, and more precisely, geometric terms, it is mainly used to calculate the sides of a figure.

From our article you will learn what a perimeter is and how it is measured on the example of basic geometric shapes.

## Perimeter Detection

Perimeter is the total length of all sides or circles of a particular shape. The perimeter is denoted by a capital letter �P�, and it can be measured in various length units, such as millimeters (mm), centimeters (cm), meters (m), etc. For different figures there are different formulas for finding the perimeter. Below we give some examples of how to find the perimeter of a rectangle and some other shapes.

## Measure the perimeter

In order to know the perimeter of a polygon, you will need a ruler. By measuring all sides of a polygon with a ruler and adding the numbers together, you will know what its perimeter is. For example, you have the sides of 13, 14, 15 and 17 centimeters, we add and get P = 13 + 14 + 15 + 17 = 59 cm. For more information about finding the perimeter of various polygons, you can learn from our article How to find the perimeter of a polygon .

If you need to know the perimeter of a complex figure (such figures can be attributed to figures with uneven lines), then for this you will need a rope or thread. With the help of these things it is necessary to describe the exact contour of the figure, and not to get confused, you can make marks on the rope with a pencil. Or you can simply cut it, and then attach all the parts to the ruler. Thus, you will learn what the perimeter is equal to in almost any complex figure.

There is another device for calculating the perimeter of complex figures: it is called a curvimeter (roller range finder). With it, you need to set the roller to any point of the figure and describe the outline of the figure with a roller. The resulting number will be equal to the perimeter. About finding the perimeter from other geometric shapes, you can learn from our article How to find the perimeter. Well, we'll tell you about several ways to change the perimeter for different shapes.

## Circle, square, equilateral triangle

Sometimes in order to determine the value of the perimeter of some figures, it is not necessary to put all the sides together, but it is sufficient to use multiplication. For example, to find the perimeter of an equilateral triangle, the side length must be multiplied by 3.For example, if the side is 12 cm, then P = 12 x 3 = 36 cm, since all sides have the same length. You can find out other interesting information about triangles by reading our article What is the perimeter of a triangle.

Let's also look at how to find out the perimeter of a circle. This is quite simple: you just need to determine the length of the circle, and you can do this by multiplying the radius �r� by the number π≈3.14 and then by 2 (P = L = 2 ∙ π ∙ r).

An even simpler task is to determine the perimeter of such a shape as a square. To do this, it is enough to know the length of one of the sides of the square, after which to multiply this value by 4 � the result obtained will be the desired number.

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