If you have the total number of hours worked for the quarter, divide by 40 to get the number of equivalent full time employee weeks, and divide that by 13 weeks in the quarter to get the average number of full time employees. Or if you have the hours worked by week, you can take the average over 13 weeks and divide by 40 hours per full time employee week.
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them