How to find the perimeter

Introduction: How to find the perimeter

How to find the perimeter. The term geometry means a measure of the Earth. It can be said without a doubt that geometry is that branch of mathematics that studies forms in the plane and space and the relationships between them. In this specific case, we speak of the perimeter. The latter represents the sum of the length of the sides that make up a figure. The quadrilateral is that geometric figure that has four sides, four corners, and four vertices. The sum of the internal angles of this figure is 360 °. The quadrilateral has two diagonals and two opposite sides with vertices that are not in common. By reading this tutorial, you can have some correct indications and valuable tips on calculating the perimeter of a quadrilateral.


  • pencil
  • ruler
  • compass

Regular figures: How to find the perimeter

It should be noted that the term quadrilateral is used when we want to refer to a two-dimensional geometric figure that is delimited by four straight lines. The perimeter of a quadrilateral is obtained by measuring and subsequently adding the length of its four sides. It is therefore not necessary to use complex formulas to calculate it.

If the quadrilateral is irregular to calculate the perimeter (P), all the sides must add, and the formula is P = a + b + c + d. While if the geometric figure is regular, all sides are equal, the formula P = 4l uses. In the rectangle which is composed of two pairs of equal sides, the formula P = 2a + 2b or P = 2 (a + b) is used. Within the category of quadrilaterals, there are the rectangle, the square, the parallelogram, the rhombus, the trapezoid (rectangle, scalene, isosceles).

Quadrilaterals with congruent sides

As already explained in the previous step, the formula for calculating the perimeter of a quadrilateral is P = sum of the four sides. It is also worth noting that some of the quadrilaterals mentioned have congruent sides. They have sides that, if they superimpose, occupy the same part of the plane. When it is necessary to calculate the perimeter of these quadrilaterals, the formula can be further simplified. However, this simplification is not possible for the rectangle trapezius and the scalene trapezius as these two quadrilaterals have no congruent side.


For example, the isosceles trapezoid has equal oblique sides. Its perimeter can calculate either by adding the sides or by the formula P = b1 + b2 + (lx 2). In other words, the minor base must add to the significant bottom plus the double product of the oblique side. Both the rhombus and the square all have congruent sides. The parallelogram is a convex polygon that has four sides parallel two by two.

It can also define as a quadrilateral with opposite sides parallel and consequently congruent. In this case, the perimeter calculation obtains by applying the formula: P = (l1 + l2) X2. It is necessary to add up the side with its consecutive side; then, you must multiply everything twice. In everyday practical applications, it is essential to know the units of measurement in which the data express (for example, centimeters, meters, etc.). If these few simple examples carefully follow, you can have more precise ideas on calculating the perimeter of any quadrilateral. At this point, there is nothing left to say but to wish you a good job.
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