How To Get The Area Of A Rectangle

Download Article

A rectangle is a quadrilateral^[1] with two sides of equal length and two sides of equal width that contains four right angles. To find the area of a rectangle, all you have to do is multiply its length with its width. If you want to know how to find the area of a rectangle, just follow these easy steps.

1
Understand the rectangle. The rectangle is a quadrilateral, which means it has four sides.^[2] Its opposite sides are equal in length, so the sides along its length are equal, and the sides along its width are equal as well. If one side of the rectangle is 10, for example, then the opposite side's length will also be 10.
- Also, every square is a rectangle, but not all rectangles are squares. So treat squares like rectangles in terms of finding its area.
2

Learn the equation for finding the area of a rectangle. The equation for finding the area of a rectangle is simply A = L * W. This means that the area is equal to the length of the rectangle times its width.^[3]

Advertisement

1
Find the length of the rectangle. In most cases, you will be given the length, but if not, you can find it using a ruler.^[4]
- Note that the double hash marks on the long sides of the rectangle mean that the lengths of the two sides are the same.
2
Find the width of the rectangle. Use the same methods to find it.
- Note that the single hash marks on the wide sides of the rectangle mean that the two widths have equal length.
3

Write the length and width next to each other. In this example, the length is 5 cm and the width is 4 cm.
4
Multiply the length times the width. Your length is 5 cm and your width is 4 cm, so you should plug them into the equation A = L * W to find the area.^[5]
- A = 4 cm * 5 cm
- A = 20 cm^2
5
State your answer in square units. Your final answer is 20 cm^2, which means "twenty centimeters squared."^[6]
- You can write your final answer in one of two ways: either 20 cm.sq. or 20 cm^2.
Advertisement

1
Understand the Pythagorean theorem. The Pythagorean theorem is a formula for finding the third side of a right triangle if you know the value of two of the sides. You can use it to find the hypotenuse of a triangle, which is its longest side, or its length or width, which meet at a right angle.^[7]
- Since a rectangle is comprised of four right angles, the diagonal that cuts through the shape will create a right triangle, so you can apply the Pythagorean theorem.
- The theorem is: a^2 + b^2 = c^2, where a and b are sides of the triangle and c is the hypotenuse, or longest side.^[8]
2
Use the Pythagorean theorem to solve for the other side of the triangle. Let's say that you have a rectangle with a side of 6 cm and a diagonal of 10 cm. Use 6 cm for one side, use b for the other side, and take 10 cm as your hypotenuse. Now just substitute your known quantities into the Pythagorean theorem and solve. Here's how to do it:^[9]
- Ex: 6^2 + b^2 = 10^2
- 36 + b^2 = 100
- b^2 = 100 - 36
- b^2 = 64
- square root (b) = square root (64)
- b = 8
  - The length of the other side of the triangle, which is also the other side of the rectangle, is 8 cm.
3
Multiply the length times the width. Now that you've used the Pythagorean theorem to find the length and width of the rectangle, all you have to do is multiply them.^[10]
- Ex: 6 cm * 8 cm = 48 cm^2
4

State your answer in square units. Your final answer is 48 cm^2, or 48 cm. sq.

Advertisement

Add New Question

Question

How do I find the area in meters?

You cannot find an area in meters, because area is expressed in square meters. If the values of your rectangle sides are not in meters, then you must first convert those units to meters, and then multiply the converted values to get the area in square meters.
Question

If the problem says length is 105 breadth is 81 and other said of length is 103 and breadth is 53, how do I find the area of the rectangle?

A rectangle has 2 sides of equal length and 2 sides of equal width (breadth). By definition, the object in which you are describing is not a rectangle. The object you have is an irregular quadrilateral.
Question

How do I find the area of a rectangle when each side is a different length?

It is not a rectangle if each side is a different length. It is either an irregular shape or a trapezoid. There is no formula for finding the area of an irregular shape. The area of a trapezoid is found by multiplying its height by the average of its bases.
Question

How can I find the area of a rectangle with only one number?

If both the sides are labeled with that same number, then it is a square. Square the number to get the area. If it's not a square, you can't, unless there's more information available than you're letting on (like an equation to calculate the length of the other side).
Question

How can I find the area of a rectangle if I only know the diagonal?

The area of a rectangle is calculated by multiplying its width times its length. You'll need this info, not the diagonal, to solve the problem.
Question

How can I find the length of a rectangle if given only the area and width?

The area of a rectangle is equal to its length multiplied by its width. This equation is represented by A=L*W. If you have only the area and width, you can use the same equation to solve for the area. For example, if the area is 60 and the width is 5, your equation will look like this: 60 = x*5. Divide 60 by 5 to find x, or the length. The answer here is 12.
Question

How do I calculate the area of an irregular rectangle?

Onebluethinker

Community Answer

There is no such thing as an irregular rectangle. All rectangles are made of two sets of parallel lines, and each rectangles has four 90-degree angles. The area is calculated by multiplying the length of the rectangle by its width.
Question

If I am only given the diagonal of a rectangle how can I find the area?.

You can't with just that information.
Question

How do I find the area of a quadrilateral?

There is no area formula for a non-specific quadrilateral. There are commonly available area formulas for a square, rectangle, parallelogram, rhombus, and trapezoid.
Question

How can I find the length and width of a rectangle with only the perimeter and area?

This is a "two equations in two unknowns" situation. Write two equations, one for the area and one for the perimeter, both in terms of length and width. Solve either equation for one of the unknowns. Plug that value back into either equation, which will give you the value of the other unknown.

See more answers

Ask a Question

200 characters left

Include your email address to get a message when this question is answered.

Submit

All squares are rectangles. However, not all rectangles are squares.
If you're finding area, your answer will always be squared.

Thanks for submitting a tip for review!

About This Article

Article SummaryX

To quickly calculate the area of a rectangle, find the length of the base. Then, multiply the base by the height of the rectangle to get the area. For example, a rectangle with a base of 6 and a height of 9 has an area of 54. Be sure to include the units of the measurements in your answer. If you need to find the area if you only know the area or the length of 1 side and a diagonal, keep reading the article!

Did this summary help you?

Thanks to all authors for creating a page that has been read 518,225 times.