A price floor is a government- or group-imposed limit on how low a price can be charged for a product. For a price floor to be effective, it must be greater than the equilibrium price.

A price floor can be set below the free-market equilibrium price. In the first graph at right, the dashed green line represents a price floor set below the free-market price. In this case, the floor has no practical effect. The government has mandated a minimum price, but the market already bears a higher price.

By contrast, in the second graph, the dashed green line represents a price floor set above the free-market price. In this case, the price floor has a measurable impact on the market. It ensures prices stay high so that product can continue to be made.

A price floor set above the market equilibrium price has several side-effects. Consumers find they must now pay a higher price for the same product. As a result, they reduce their purchases or drop out of the market entirely. Meanwhile, suppliers find they are guaranteed a new, higher price than they were charging before. As a result, they increase production.