Full-Time Equivalent (FTE) Calculator (incl. US ACA 120-hour rule)

Understanding the full-time equivalent (FTE) calculator — concept and principle

This calculator converts a mix of full-time and part-time staff into full-time equivalents (FTE). It gives the general FTE based on hours, the headcount, the total part-time hours and a separate count under the US Affordable Care Act (ACA) rules for the month. Employers, HR teams and accountants use it for budgeting, reporting and checking whether ACA employer rules may apply.

Hours turned into full-time staff — with the default inputs: 22.17 FTE.

How it is calculated

General FTE = full-time employees + total part-time hours ÷ full-time hours per month
Full-time hours per month: 40 × 52 ÷ 12 = 173.33 by default
ACA: anyone with 130 or more hours in the month counts as full-time
ACA FTE from the rest = Σ min(hours, 120) ÷ 120
ACA count = full-time employees + part-timers with 130+ hours + ACA FTE

Enter each part-timer's hours for the month, one per line or separated by spaces.

The principle

FTE expresses working time in units of one full-time job, so a team of mixed contracts can be compared with a budget or another team. Two people working half time each make 1 FTE. The ACA count is a legal measure with its own rules set by the US Internal Revenue Service: 30 hours a week or 130 hours a month means full-time, and other employees' hours are pooled in 120-hour units. An employer averaging 50 or more full-time plus FTE employees over the previous calendar year is an applicable large employer.

Worked example

Defaults: 18 full-time employees; part-time hours 80, 64, 120, 96, 140, 40, 72, 110; 173.33 full-time hours.

Total part-time hours = 722.
FTE from part-time staff = 722 ÷ 173.33 = 4.17; total FTE = 18 + 4.17 = 22.17.
Headcount = 18 + 8 = 26.
ACA: one part-timer has 140 hours, so 1 counts as full-time.
The other seven total 582 hours (none above 120); 582 ÷ 120 = 4.85 ACA FTE.
ACA count = 18 + 1 + 4.85 = 23.85.

Each point is the calculator re-run with only “Full-time employees” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Full-time employees	Total FTE (all hours ÷ full-time hours)
4.5	8.67
9	13.17
13.5	17.67
18	22.17
22.5	26.67
27	31.17
36	40.17

How to read the result

General FTE is the right figure for staffing budgets and productivity ratios. The ACA figure for one month is only one of twelve: the large-employer test averages the twelve monthly counts of the previous year. A month near 50 is a reason to track all months carefully and take professional advice.

Common mistakes

Using contracted hours instead of hours actually worked or paid.
Counting more than 120 hours for one part-timer in the ACA FTE pool.
Treating a single month's ACA count as the annual test.
Mixing weekly and monthly hours.

Keep in mind: ACA rules include special cases (seasonal workers, measurement periods) not covered here. This is not legal or tax advice.

Frequently asked questions

How many hours is 1 FTE?

It depends on your standard: with 40 hours a week, about 173.33 hours a month or 2,080 hours a year.

What is an applicable large employer under the ACA?

An employer with on average at least 50 full-time employees, including full-time equivalents, during the previous calendar year.

Why does the ACA cap hours at 120?

The IRS rule counts at most 120 hours per non-full-time employee per month when calculating FTEs.

Sources: U.S. Internal Revenue Service, "Determining if an employer is an applicable large employer"

Checked 9 Nov 2026. General FTE: hours worked ÷ full-time hours (arithmetic). ACA rules: U.S. Internal Revenue Service, “Determining if an employer is an applicable large employer” (Affordable Care Act, employer shared responsibility) — 30 hours a week or 130 hours a month = full-time; FTEs = non-full-time hours (max 120 each) ÷ 120; 50-employee threshold averaged over the prior year.

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