Direct square proportion is the relationship between two things in which the quantity of one is directly proportional to the square of the other. In this relationship, the ratio of the first to the square of the second is a constant.

An example of direct square proportion is when a circle is directly proportional to the square of its radius. This example is expressed by an equation stating that the area of a circle is equal to the constant multiplied by the square of the radius. Direct proportion is the relationship between two things in which the quantity of one is directly proportional to the other, without the second quantity being squared. In this type of proportion, the two quantities change by the same factor.