Inverse Proportion Definition

What Inversely Proportional Means in Science

The volume of an ideal gas is inversely proportional to its pressure (Boyle's law).
The volume of an ideal gas is inversely proportional to its pressure (Boyle's law). Multi-bits / Getty Images

Inverse proportion is the relationship between two variables when their product is equal to a constant value. When the value of one variable increases, the other decreases, so their product is unchanged.

y is inversely proportional to x when the equation takes the form:

y = k/x

or

xy = k

where k is a constant

In contrast, directly proportional variables increase or decrease with each other.

Inversely Proportional Examples

  • Speed and travel time are inversely proportional. The faster you go, the less time it takes to complete your trip.
  • The volume of an ideal gas is inversely proportional to the pressure of the gas (Boyle's Law)