The perimeter of any polygon (including **triangle perimeter**) is calculated by the definition of the perimeter. To do this, simply add up the lengths of all sides of the polygon.

P_{Abcde} = AB + BC + CD + DE + EA = 3 + 4 + 3 + 2 + 2 = 14 (cm)

## How to find the perimeter of a rectangle?

Below in the article you will learn what it is and how to find the perimeter of a rectangle if its sides are known. And also how to find the sides of a rectangle, if its perimeter is known. And one more interesting construction applied task.

The perimeter is the length of the geometric shape along its outer border.

The perimeter of a rectangle is the sum of the lengths of its sides.

Formulas for calculating the perimeter of a rectangle: P = 2 * (a + b) or P = a + a + b + b.

We summarize! In order to calculate the perimeter of a rectangle, it is necessary to add all its sides.

**Typical mathematical and practical problems:**

Initial data: Define the perimeter of a rectangle with side lengths of 5 cm and 10 cm.

According to the formula, the perimeter of the rectangle is = 2 * (5 + 10) = 30 cm.

Input data: Determine the sides of the rectangle expressed as integers if the perimeter of the rectangle is 10.

Using the formula, we determine the sum of the lengths of the sides (a + b) = P / 2 = 10/2 = 5

The integer values of the sides can only be 1 + 4 = 5 and 2 + 3 = 5

Answer: The lengths of the parties can be only 2 and 3 or 1 and 4.

__Task number 3 (practical):__

Initial data: Determine the number of skirting boards in sufficient quantity to repair the floor in a room 5 meters long and 3 meters wide, if the length of one skirting board is 3 meters.

Room Perimeter = 2 * (5 + 3) = 16 meters

Number of skirting boards = 16/3 = 5.33 pieces

Usually in construction stores, skirting boards are not sold per meter, but individually. Therefore, we accept the following integer. This is six.

Answer: The number of skirting boards is 6 pieces.

The solution to the problem of calculating the perimeter is a fairly simple mathematical problem, but of very important practical importance, for example, in the construction or general planning of a territory.

This page provides the easiest online calculator for calculating the perimeter of a rectangle. With this program you can find the perimeter of a rectangle in one click, if its length and width are known.

### Entering data in a calculator to calculate the perimeter of a rectangle

You can enter numbers or fractions in the online calculator. Read more in the rules for entering numbers.

**N.B.** In the online calculator, you can use the values in the same unit of measure!

If you have difficulty converting units, use the unit of distance and length converter.

## How to find the perimeter of a rectangle

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Calculating the perimeter of a rectangle is a fairly simple task. All you need to know is the width and length of the rectangle. If these values are not given, you need to find them. This article will tell you how to do this.

## Theory. Rectangle perimeter

**Rectangle perimeter** ABCD is equal to twice the sum of the sides adjacent to one corner.

where P is the perimeter of the rectangle,

a is the length of the first side,

b is the length of the second side.

You can enter numbers or fractions (-2.4, 5/7,.). Read more in the rules for entering numbers.

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My name is Dovzhik Mikhail Viktorovich. I am the owner and author of this site, I have written all the theoretical material, and also developed online exercises and calculators that you can use to study mathematics.