Home / United States / Math Classes / Calculators / Perimeter of Rectangle Calculator

The perimeter of a rectangle calculator is a free online tool that calculates the perimeter, width, or length of a rectangle. The calculation is done when any two of the measurements among the rectangle’s perimeter, width or length are known to us. The perimeter of a rectangle calculator tool from BYJU’S displays the desired result in a fraction of a second....Read MoreRead Less

**1.**

Identify the two quantities out of the three quantities of the rectangle, the length, width and perimeter, that are known, and enter them into the respective input fields.

If you enter length and width, the perimeter will be calculated.

If you enter length and perimeter, the width will be calculated.

If you enter width and perimeter, the length will be calculated.

**2.**

Select the appropriate units for the input and output.

**3.**

Click on ‘Solve’ to obtain the required quantity.

**4.**

Click on the reset button to enter new inputs.

**5.**

You can check ‘Show steps’ by clicking in the box to understand the stepwise method for obtaining the answer.

**6.**

You can also play around with different input values by clicking ‘example’ to test out random values.

**7.**

Click on the ‘explore’ button to see the changes in the perimeter of a rectangle when the length and the width are changed. Click on the “play” button to see the animation of the perimeter.

**8.**

When on the ‘Explore’ page, click on the ‘Calculate’ button if you want to go back to the calculator.

First, let’s understand what a rectangle is. A rectangle is a four-sided, two-dimensional figure. A rectangle’s opposite sides are parallel to each other and of equal length, and each interior angle is 90 degrees.

Now, what is the perimeter? The perimeter is the measure of the length of the boundary of a shape.

So this means that the perimeter of a rectangle is equal to the sum of its four sides. Let’s call the longer side of the rectangle as its length and the shorter side as its width. Since the opposite sides are equal in measure, the formula for the perimeter of a rectangle is written as:

Perimeter = Length + Length + Width + Width = 2 (Length + Width)

Let’s shorten this further!

P = 2 (l + w), where “P” is the perimeter, “l” is the length and “w” is the width.

**Example 1:** Find the perimeter of a rectangle whose length is 25 feet and width is 12 feet.

**Solution :**

Perimeter of rectangle (P)

= 2(l + w) Formula for perimeter of rectangle

= 2 × (25 + 12) Substitute values of length and width

= 74 feet Simplify

Thus, the perimeter of the rectangle is 74 feet.

**Example 2: **Calculate the length of a rectangle whose width and perimeter are 10 cm and 48 cm, respectively.

**Solution :**

Perimeter of rectangle (P)

P = 2(l + w) Formula for perimeter of rectangle

\(l = \frac{p}{2}-w\) Solve for l

\(l = \frac{48}{2}-10\) Substitute values of w and P

l = 14 cm Simplify

Thus, the length of the rectangle is 14 cm.

Frequently Asked Questions on Perimeter of a Rectangle Calculator

The perimeter of a rectangle is the sum of the length of all its sides. So to calculate the perimeter, we simply add the measures of the sides of a rectangle.

We know that the opposite sides of a rectangle are equal, so let’s assume the length of one side to be “l” and the other adjacent side to be “w”. Then, the perimeter of the rectangle will be l + w + l + w = 2l + 2w = 2(l + w).

Area of a rectangle is length × width. Suppose we know the perimeter of a rectangle and only one value out of either the length or width, we can still calculate its area. For example, if the perimeter and width is known to us, then the length can be calculated, Perimeter = 2(length + width), then

\(\text{length}=(\frac{\text{perimeter}}{2})-\text{width}\)

Now the values needed to calculate the area of a rectangle, width and length, are now known, hence we can calculate its area.

All interior angles of a rectangle measure 90 degrees. So the adjacent sides of a rectangle are perpendicular to each other. Therefore, the angle between the sides that make up the width and length of a rectangle is 90 degrees.

The perimeter is defined as the sum of the lengths of the sides of an object. The perimeter of different flat shapes are measured in any unit that is used to measure length, including metres, centimetres, miles, feet, inches, etc.

We need to understand how to calculate perimeter for everyday use. Let’s say a person needs to fence a garden, they would need to calculate the perimeter first to decide the length of the fencing. Also professionals such as architects and engineers use the perimeter of shapes to solve multiple challenges.