Consumer Surplus vs Deadweight Loss

Consumer surplus is the difference between the maximum price a consumer is willing to pay and the actual price they pay.

It measures the net benefit consumers receive from buying a good or service. On a demand curve, it is the area below the demand curve and above the price paid, up to the quantity purchased.

Deadweight loss is the loss of total surplus that occurs when a market is not at its efficient competitive equilibrium.

It measures mutually beneficial trades that fail to occur because of a price control, tax, monopoly, or externality. On a supply-and-demand graph it is the triangular area between the demand and supply curves over the units no longer traded. A market is allocatively efficient when deadweight loss is zero.