Whether you need to know the area of a carpet, a land parcel, a TV screen or a window, this area of a rectangle calculator will solve your problem in a blink of an eye! All you have to do is input the length and width, and allow this rectangle calc to find the values of P (perimeter) and A (area).

Take a look at the trapezoid and circle calculators for other geometric shapes, or keep reading to learn how to find the area of a rectangle!

How to find the area of a rectangle?

area of a rectangle

The image above shows a typical rectangle. It has four sides and four right angles. The lengths of its sides are denoted with a and b, while the length of the diagonal is denoted with d.

If all sides of the rectangle have equal lengths, it is called a square.

Our area of a rectangle calculator uses the following formulas:

  • For the area: A = a * b

  • For the perimeter: P = 2 * (a + b)

  • For the diagonal: d² = a² + b²

If you're interested in 3D solids rather than two-dimensional shapes, check out the surface area calculator.

Rectangle calc: find A (area)

  1. Choose the length of the rectangle - for example, a = 5 cm.
  2. Decide on the width of the rectangle - for example, b = 6 cm.
  3. Multiply these two values: A = 5 * 6 = 30 cm².
  4. The area of the rectangle is 30 cm².

Rectangle calc: find P (perimeter)

  1. Choose the length of the rectangle - for example, a = 5 cm.
  2. Decide on the width of the rectangle - for example, b = 6 cm.
  3. Add these two values: a + b = 5 + 6 = 11 cm.
  4. Multiply the result by 2: P = 2 * 11 = 22 cm.
  5. The perimeter of the rectangle is 22 cm.

Rectangle calc: find D (diagonal)

  1. Choose the length of the rectangle - for example, a = 5 cm.
  2. Decide on the width of the rectangle - for example, b = 6 cm.
  3. Calculate a to the power of two: a² = 25 cm².
  4. Calculate b to the power of two: b² = 36 cm².
  5. Add these two values: a² + b² = 25 + 36 = 61 cm².
  6. Finally, take a square root of the result: d = √(a² + b²) = √61 - 7.81 cm.
  7. The length of the diagonal is 7.81 cm.

Naturally, instead of calculating all of these values manually, you can go ahead and use this area of a rectangle calculator. You can also use it in reverse - for example, to calculate the width of a rectangle with a known length and perimeter.

Golden rectangle

golden rectangle

A special type of a rectangle, called the golden rectangle, is shown in the image above. Such a rectangle fulfills the following condition:

(a + b) / a = a / b = ϕ

where φ is the golden ratio equal to 1.618.

Bogna Haponiuk

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Area of a Rectangle Calculator