How Do You Calculate "pro Rata" Salary?

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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.