The number of productive hours per FTE can vary. Not only do different companies have different policies for vacation and sick leave, there are other factors such as company specific training (non-reimbursable), jury duty, reserve duty, time off for short term disability, pregnancies, etc. I believe the 1980 is an average based on a large population taking into consideration all non productive time off. That?s the reason that you end up with a partial day. I?ve seen the number used for years, but I?ve not validated whether it is still a representative average.
The specific number of hours equivalent to an FTE for a particular contract can vary. If looking at a small population of employees, a company may not factor in some of these potential causes of lost productivity. If the contract is to provide 5 FTEs or the hours are equivalent to 5 FTS, then it would too inefficient to have a sixth person on staff just in case an employee gets pregnant and needs a couple of months off. If the work force is several hundred, history will tell you that over the course of a year, X employees will go out on maternity leave, Y employees will be out several months on reserve duty, Z weeks will be spent on jury duty, etc. The demographics of the work force, male/female, young/old, can also impact it.
Because of the variables, I am always hesitant to dictate the number of hours per FTE. Tell the contractor what is required, whether that is to perform these tasks or a need for 20 guards, 40 hours a week. Let the company figure out how many people need to be hired. If you need to know how the FTEs relate to the number of hours, have the company provide number of productive hours they used and the basis for that number.