What is an FTE, how is it used, and what are the varieties of FTE calculation that you might see in academia?
An FTE stands for Full-Time Equivalent and is the unit of calculation for counting faculty positions or student enrollment at a university.
For faculty positions
A 1.0 FTE position is nominally a full-time position for one faculty member. If a department has 4 FTE, then you can expect that it has four full-time faculty at minimum (see adjunct FTEs below).
Someone may have a split FTE such that for example, half of their FTE belongs to one department and half belongs to another -- e.g., Prof. Alice could be 0.5 Math and 0.5 Computer Science.
The ratio can vary so that Prof. Bob could be 0.25 Physics and 0.75 Geology.
Some spousal hires are structured so that Profs. Alice and Bob are both 0.5 in the same department (or even separate units).
Some universities have "zero FTE" positions. This is often used to indicate affiliate faculty. For example, Prof. Alice could be 0.5 FTE in Math, 0.5 FTE in CompSci, but also have a 0.0 FTE slot in Physics.
Adjuncts are occasionally included in FTE but the exact calculation of an adjunct to a regular FTE varies considerably by university.
Bifurcated FTE Ranks: Some universities have separate "senior faculty (tenured)" FTE and "junior faculty (untenured)" FTE calculations, so that a 4 unit program may have 2 senior FTE and 2 junior FTE.
More than 1.0 FTE: Some universities also allow for someone to have more than 1.0 FTE. Since 1.0 FTE is calculated on a 9 month term (in the United States), one could conceivably have up to a 1.33 FTE by working through the summer. The NSF and others often restrict summer salary to .25 so the max under those grants is 1.25 FTE.
For student enrollment
Student enrollment can also be measured in FTE. "FTE enrollment" is computed as the sum of credits carried by all enrolled students, divided by the number of credits in a full-time load at that institution, school, or department.
For example, at the University of Colorado, a full-time undergraduate load is 30 credits a year, and a full-time graduate load is 24 credits per year, therefore
Student Full-Time Equivalent Enrollment (SFTE) = total undergraduate student credit hours in a fiscal year divided by 30 plus total graduate student credit hours in a fiscal year divided by 24
This measure may be used for budgeting, resource allocation between departments or within a department, facilities planning, faculty hiring, and other similar considerations.