Salespeople in many businesses earn a small salary supplemented by a commission. The commission compensates the employee based on a percentage of the sales, according to the book "Contemporary Business Mathematics for Colleges." The gross sales refers to the amount of money taken in from sales before factoring in any business costs. Use this figure to calculate a salesperson's commission earnings.

Convert the percentage of commission to a decimal by dividing the commission rate by 100. For instance, if an employee earns a 5 percent commission, 5/100 = 0.05.

Find your employee's gross sales by adding up all of his sales for the pay period to find the gross amount. For example, if the employee had sales in a month of $25,000, $70,000 and $5,000, his total gross sales would be" $25,000 + $70,000 + $5,000 = $100,000.

Multiply the commission as a decimal by the gross sales to find the commission based on the gross sales. For example, if an employee sold $100,000 at 5 percent commission: $100,000 x 0.05 = $5,000.

Repeat the process for calculating commission for additional employees.