Rectangle area calculator

Calculate the area of a rectangle based on the formula for calculating its area, which tells us that, if we want to calculate the area of a rectangle, we have to multiply its base by its height. In the case of the squareBoth values are equal, so it would be enough to square the value of one of its sides, but in the rectangle there are differences between one and the other.

How to calculate the area of a rectangle

Rectangle area calculator
The rectangle is one of the easiest regular figures to calculate its area. We simply have to multiply its base by its height and that's it. This is expressed mathematically by the following formula:

Area of rectangle = base x height

For example, if we are given a rectangle whose base measures 6 centimeters and its height measures 3 centimeters, what is its area? To calculate it, we apply the above formula and we have that:

Area = 6 cm x 3 cm = 18 cm2

Calculate the diagonal of a rectangle

If what we want is calculate how long the diagonal of a rectangle isthen we have to resort to the Pythagorean Theorem.

Pythagorean Theorem

If we look at the figure above, we can see that that triangle is half of a rectangle to which we have made a cut along its diagonal. Thanks to this, we can calculate the length of the diagonal easily by applying the following formula:

Formula Hypotenuse

When we solve the operation, we already have the value of the diagonal.

Calculate the area of an irregular rectangle

If we are asked to find the area of an irregular rectangle then we will not be able to apply the formula we have seen. In this case, what we have to do is to divide the figure into different triangles and calculate the area of each of them. We explain how to calculates the area of a triangle in the link we have just left.

When you have the surface of all triangles composing the irregular rectanglesimply add up all their values and the result you are looking for.

Area of a 3D rectangle

Rectangular prism

If we are asked to calculate the area of a 3D rectangleWhat we have to do is to calculate the area of each of its 6 faces. For example let's find the area of the three-dimensional rectangle in the figure above.

To this end, we will calculate the surface area of the 3 different faces. The remaining 3 missing sides are equal and thus we save calculations by multiplying by 2:

Side 1: 4 x 3 = 12 cm2

Side 2: 4 x 6 = 24 cm2

Side 3 6 x 3 = 18 cm2

Total area of the 3D rectangle: 2 x (12 + 24 + 18) = 108 cm2

If you have any doubt about how to calculate the area of a rectangle, leave us a comment and we will help you as soon as possible.

8 thoughts on “Calculadora de área de un rectángulo”

  1. Hi, how are you? I was given this exercise:
    The width of a closet is four times its height. The measure of the depth coincides with the height. If the prerimeter of the closet is 1440 cm, express the measurements of the closet in meters.

    • Hello Lautaro,

      The exercise you propose is simple, let's see it step by step.

      The cabinet is shaped like a rectangular prism and in this case, its formula is:

      P = 4L + 4B + 4C


      - L: the height of the cabinet
      - C: depth
      - B: the width of the cabinet

      1 - We are told that the width of a closet is four times its height, therefore:

      B = 4L

      2 - We are told that the depth is equal to the height. Therefore:

      C = L

      If we take these equivalences to the initial formula we have that:

      P = 4L + 4B + 4C = 4L + 4(4L) + 4L = 24L = 1440cm

      Now we clear and we are left with:

      L = 1440cm / 24 = 60 cm

      Now we substitute in each unknown and we have the resulting dimensions of the cabinet:

      Height: 60cm
      Depth: 60cm
      Width: 240cm

      I hope it has been helpful.


    • Hello Samuel,

      We don't quite understand your question. The rectangle is a plane figure, it has no faces.

      In case you are referring to a rectangular prism, you could know the area of the base from a face that is equal to the base since the rest will be different.

      Best regards!

  2. Hi, how is it going? I have a question, I was given the following exercise:
    - we want to paint the 4 walls and the ceiling of a living room that is 12m long, 7m wide and 3.5m high. Knowing that it has 1 door of 2x1m, and 2 windows of 2x2m. how much surface will have to be painted? There are 25m2 paint cans available. How many paint cans are needed?

    • Hello Nicolas,

      You are asked to calculate the surface of each wall, taking out the area of windows and doors. It is very simple.

  3. I have to calculate the area of a 3d rectangle of 28 × 15 × 9 cm, according to this page should give me 72.930 cm but, in the exercise comes the total value that should give me and says that it is 1614 cm, what am I doing wrong?

    • Hello Alma,

      If you want to calculate the area, it cannot be 3D because then we would be talking about calculating volume and for that I recommend the calculator of a rectangular prism:

      If what you want is to calculate area, then you have one of the measurements you give us left over.


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