The short version
FTE = total hours worked ÷ full-time benchmark hours. Add up everyone’s weekly hours — full-timers at the benchmark, part-timers at their actual average — and divide by what “full-time” means at your company (usually 40). The answer is your workforce expressed as full-time people: 20 employees can be just 16.0 FTE if several are part-time. Run your numbers in the FTE calculator; the rest of this guide is the method behind it.
The standard formula, in three steps
Step 1: convert everyone to weekly hours. Full-timers: count × benchmark. Part-timers: count × their average weekly hours. With 12 full-timers on a 40-hour week and 8 part-timers averaging 20 hours: 12 × 40 = 480, and 8 × 20 = 160.
Step 2: add them. 480 + 160 = 640 hours per week across the whole staff.
Step 3: divide by the benchmark. 640 ÷ 40 = 16.0 FTE. As one formula:
FTE = (full-time count × benchmark + part-time count × average hours) ÷ benchmark
Worked example: the 16.0-FTE bakery
Bright Side Bakery has 12 full-timers and 8 part-timers averaging 20 hours a week, on a 40-hour benchmark. Full-time hours: 12 × 40 = 480. Part-time hours: 8 × 20 = 160. Total: 640. Divided by 40: 16.00 FTE — even though headcount is 20. The four-FTE gap is the part-time share of the workforce, and it’s exactly the gap that trips up staffing budgets built on headcount alone.
The IRS monthly method (the 120-hour rule)
The Affordable Care Act’s employer test does not use the standard formula — it uses a fixed monthly divisor. The IRS method: add up every part-timer’s hours for the month, divide by 120, then add your full-time headcount (30+ hours a week). For the bakery: monthly part-time hours = 8 × 20 × 52 ÷ 12 = 693.3; 693.3 ÷ 120 = 5.78; plus 12 full-timers = 17.78 FTE.
Notice the two methods disagree — 16.0 vs 17.78 — and both are “right.” Use the standard method for budgeting, staffing plans, and grant reporting; use the IRS monthly method for the legal employer-size test. Never compare a standard-method number against the 50-FTE legal line.
The 50-FTE line that matters
Average 50 or more full-time equivalents — full-time employees plus full-time equivalents, measured month by month across the prior calendar year — and you’re an Applicable Large Employer under the ACA. That brings the employer shared responsibility provisions: offer affordable minimum-value coverage to full-time staff or face potential penalties. Growing companies watch this line the way drivers watch a speed limit, because crossing it changes the compliance workload overnight. The calculator shows your distance from it on the IRS monthly figure.
Four mistakes that skew FTE
1. Using headcount as FTE. Twenty people is not 20 FTE unless everyone is full-time. Budgets built on headcount overstate available labor by the part-time gap.
2. Forgetting the benchmark moves the answer. The bakery’s staff is 16.0 FTE on a 40-hour week but 20.0 FTE on a 32-hour week — same people, same hours. Always state your benchmark when you report FTE.
3. Counting contractors. 1099 contractors, agency temps, and owners are generally excluded from FTE — which is one more way the 1099 vs W-2 choice changes the math beyond taxes.
4. Mixing the methods. Comparing a standard-method FTE against the 50-FTE legal line understates (or overstates) where you stand. Match the method to the question.
Frequently asked questions
How many hours is 1.0 FTE?
Whatever your organization defines as full-time — commonly 40 hours a week, but 37.5 and 32 are real benchmarks too. 1.0 FTE is one full-time workload, not a fixed number of hours.
Can FTE be higher than headcount?
Yes. If everyone works overtime — say 20 people averaging 45 hours on a 40-hour benchmark — FTE is 22.5 against a headcount of 20. FTE measures work, so sustained overtime pushes it above the body count. Check what that overtime costs before it becomes the plan.
Do seasonal workers count?
For general FTE math, yes — their hours count like anyone’s. For the ACA employer test, seasonal workers get special treatment: months where they push you over 50 may be disregarded if they worked 120 days or fewer. The details are fiddly; confirm with benefits counsel before relying on the exception.
Is FTE the same as headcount?
No. Headcount counts people; FTE counts workload. A company with 20 employees and 16.0 FTE has a 20% part-time share — useful context for scheduling, benefits planning, and hiring.