A pro rata salary is calculated by dividing someone's annual, full-time salary by any portion of an employment period that is less than a year, according to Discovering People. For example, if a full-time employee makes $52,000 per year, the pro rata salary for one week is $1,000 because there are 52 weeks in a year. Divide $1,000 by 40 hours per week, and the hourly wage is $25.
Pro rata employment rates are for part-time, seasonal or temporary workers who make the equivalent of a full-time salary for less than one year. Discovering People indicates the hourly wage is multiplied by the hours worked per week for a weekly pro rata salary. At $25 per hour and 20 hours per week, a pro rata employee makes $500 per week at the same rate as the full-time worker who makes $52,000 a year.
One advantage to pro rata employment is that employees have the same benefits of full-time workers such as health insurance, paid time off, holidays and maternity leave. The Site explains that someone who works 20 hours per week gets half the holiday hours and half the maternity leave of full-time employees.
The term "pro rata" is a Latin phrase meaning "proportional." The Free Dictionary reveals that pro rata is divided according to someone's participation or involvement.