Companies can calculate their sales revenue from a derived number based on the cost of a unit and the number of units sold. Generally, the cost of a unit times the number of units sold equals the sales revenue for the company. However, companies often have more than one product and therefore calculate the sales revenue for individual products, then combine the revenue figures in a single sum.

Determine the cost of a unit and the number of units sold for each product line. For example, Firm A sells widgets and each widget sells for £3 a unit. Firm A sells 100,000 units during the year.

Multiply the cost per unit by the number of units sold. In our example, £3 multiplied by 100,000 equals £390,000 of sales revenue.

Combine the sales revenues from other products. For example, if Firm A also sells buckets that produce sales revenue during the year of £130,000, its total sales revenues is £390,000 plus £130,000, which equals £520,000.