What is consumer surplus?

The difference between the actual price which the consumer is willing to spare for any commodity and the actual price which is paid by them is known as consumer surplus.  Consumer satisfaction is gauged by overall social surplus which is comprised of consumer surplus and producer surplus in terms of utility.

It is a measure of the actual benefit gained by the consumer in the transaction as per the value of the good as seen by the consumer. Consumer surplus is positive when the consumer is ready to pay more than the actual price of the good. It is found by the area which falls below the demand curve and above the price line. It is infinite in case of the inelastic demand curve and zero in case of a perfectly elastic demand curve.