In business, it is a frequent occurrence that you need to ship several boxes or cases through the mail. Each mail service, such as FedEx, UPS or the USPS, charges different rates for shipping. However, if you ship a lot of packages at one time or over the course of a year, you may receive a discounted rate. When you finally receive your bill, the bill will show the expense for all the packages. To track expenses, it's easy to look at the expense on a per case basis.

Use your invoices from your shipping company and add together your total shipping costs for the year. For example, assume shipping cost you $50,000 one year.

Determine the number of shipments you made during the year. In the example, assume you shipped 60,000 cases.

Divide the total amount you spent on shipping by the total number of shipments you made. In the example, $50,000 divided by 60,000 cases equals $0.84 per case shipped.