Dimensions of a Rectangle Calculator

Created by Vishnuvardhan Shakthibala
Reviewed by Rijk de Wet
Last updated: Jun 05, 2023

If you're wondering how to find dimensions of a rectangle given area and perimeter, do not fret — our dimensions of a rectangle calculator helps you find the dimensions of a rectangle right away.

If you want to know more about rectangles and how to find their dimensions, please continue to read the below article.

What are the dimensions of the rectangle?

A rectangle is a 2-dimensional geometrical shape formed by four perpendicular sides. Out of four sides, two sides are unique, and the other two sides are similar to the unique sides. These two unique sides are the dimensions of a rectangle.

How to use our "Dimensions of a Rectangle Calculator"?

If you're unsure of how to use the "dimensions of a rectangle calculator", just follow these steps:

  1. Input the perimeter (P);
  2. Input the area (A); and
  3. Right away, you will get the dimensions of the rectangle.


How do you find the dimensions of a rectangle?

To find the dimensions of a rectangle:

  1. Rewrite the perimeter equation P = 2(a+b) in terms of one of the dimensions, like so: b = P/2−a.
  2. Now insert the above equation into the equation for the area (A):
    • The area equation is given as A = a×b.
    • Substituting b inside A = a×b, we get A = a(P/2−a).
  3. Solve the quadratic equation a² − (P/2)×a + A = 0 to get a.
  4. Find b using b = P/2−a or b = A/a.
  5. Hurray! Now you know how to find the dimensions of a rectangle given area and perimeter.

How do you find the dimensions of a square?

To find the dimensions of a square with side length a:

  1. if you have the perimeter (P), write the perimeter equation P = 4a in terms of the side length, as a = P/4.
  2. If you have the area (A), write the area equation A = a² in terms of the side length, as a = √A.
  3. You can see that to find dimensions of a square, you just have to know either area (A) or perimeter (P).

How to find the dimensions of a square whose area is 20 m²?

To find the dimensions of a square with a given area, you just have to take the square root of A. Therefore, one of the dimensions of a square is a = √20 = 5 m.

What is the perimeter of a rectangle?

The perimeter (P) of a rectangle is the sum of all the individual sides of a rectangle, i.e., P = 2x(a+b).

Vishnuvardhan Shakthibala
Image of a rectangle with sides a and b, diagonal d, perimeter and area marked.
Area (A)
Perimeter (P)
Length (a)
Width (b)
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