Formula for perimeter of rectangle

Learn and know what is a perimeter and how to find it for a rectangle. All the school going students should know about this concept. Perimeter and areas are a very important concept.

Formula for perimeter of rectangle

Do you know what is a perimeter? A Perimeter is nothing but the sum of all the sides of the given diagram. Now in this case i.e. for a rectangle sum of all the sides gives the perimeter.

The Formula for finding the perimeter of rectangle:

Let us consider a rectangle PQRS with length as “L “units and breadth as “B” units.

Formula for perimeter of rectangle

Therefore, the perimeter of rectangle PQRS is = 2 (L + B) units.

Proof for the perimeter of rectangle formula:

Formula for perimeter of rectangle

We know that in a rectangle opposite sides are always equal in length.

PQ = RS = L units

In the same way, QR and PS are equal in length.

QR = PS = B units

Perimeter of rectangle

  = sum of all its sides

  = PQ + QR + RS + SP

  = L + B + L + B

  = 2L + 2B

  = 2 ( L + B)

Therefore, perimeter of rectangle is also defined as twice the sum of its length and breadth.


*What is the perimeter of rectangle whose length is 5 cm and breadth is 17 cm.


We know that P = 2(L + B)

                              = 2 (5 + 17)

                              = 2 (22)

                              = 44 cm.

*Find the length of the rectangle whose perimeter is 40 cm and breadth is 10cm.



Breadth = 10 cm

Perimeter = 40 cm

We know that

P          = 2(L + B)

40        = 2 (L + 10)

40/2    = L + 10

20        = L + 10

20 – 10 = L

10 =  L

Therefore, length of rectangle is 10 cm.

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