There are several ways to calculate cost reduction. One common method is to compare the cost of goods or services before and after a change has been made. This can be done by looking at the total cost, the unit cost, or the marginal cost. Another approach is to compare the cost of a good or service with that of a similar good or service. This can be done by looking at the price elasticity of demand or the cost structure. Finally, one can also look at how technological changes or other factors have affected the cost of production.