An FTE calculator converts a workforce into a common unit. Thirty-two people, some working five days and some working one, cannot be added up meaningfully — the sum tells you nothing about capacity, nothing about cost per unit of output, and nothing that can be compared with last year if the mix has changed. Expressing everyone as a fraction of a standard full week solves that, and the result is the number that budgets, capacity plans and most regulatory thresholds are actually built on.
Arb Digital publishes this in the free tool library at arbsbuy.com for owners and managers who need one defensible figure rather than three arguable ones. It is a different job from the live employee cost calculator, which prices a single employee from salary upward. This page works at the workforce level: it takes a mixed team and reduces it to equivalents, then applies a cost per equivalent that you supply.
What This FTE Calculator Does
Enter how many full-time employees you have and what a full-time week means in your organisation, then the combined weekly hours worked by part-time staff and by temporary or seasonal staff. The calculator divides each group's hours by the standard week and adds the results to the full-time count.
The headline is total FTE. The grid shows total headcount alongside it, so the two are never confused, plus the part-time contribution in FTE terms, the FTE-per-head ratio, and the annual cost of the whole workforce at the cost per FTE you enter. The bars split total FTE between the three groups, which is the fastest way to see how much of your capacity is permanent full-time and how much is not.
Keeping temporary staff in a separate line is deliberate. Two organisations with identical total FTE are in very different positions if one has 6 percent of its capacity on temporary arrangements and the other has 30 percent, and a single blended number hides that completely.
How to Use It
- Define the standard week first and use the same definition everywhere. A 37.5-hour standard and a 40-hour standard produce different FTE figures from identical staff, and neither is wrong — but mixing them is.
- Enter combined hours, not averages. Eleven part-timers working 214 hours between them is one input, not eleven.
- Decide contracted or actual hours and be consistent. Contracted hours give a capacity plan; actual hours including overtime give a workload measure. They answer different questions.
- Build the cost per FTE from your own payroll — salary plus employer taxes, benefits, insurance and any overhead you allocate to people.
- Recalculate whenever the mix changes, not just when headcount does. Converting two full-timers to four half-timers leaves FTE unchanged and raises headcount by two.
The Formula / How It's Calculated
The general formula is FTE = full-time employees + (part-time hours ÷ standard weekly hours) + (temporary hours ÷ standard weekly hours). Total headcount is simply the number of people. FTE per head is FTE divided by headcount, and annual cost is FTE multiplied by the cost per equivalent.
Work the defaults. There are 18 full-time employees against a 40-hour standard week, contributing 18.00 FTE. Eleven part-time staff work 214 hours a week between them, which is 214 ÷ 40 = 5.35 FTE. Three temporary staff work 60 hours a week, which is 60 ÷ 40 = 1.50 FTE. Total FTE is 18.00 + 5.35 + 1.50 = 24.85.
Headcount is 18 + 11 + 3 = 32 people, so FTE per head is 24.85 ÷ 32 = 0.777. In other words the average person in this organisation works about 78 percent of a full week. Annual cost at 72,000 per FTE is 24.85 × 72,000 = 1,789,200.
The shares follow: full-time is 18.00 ÷ 24.85 = 72.43 percent of capacity, part-time is 21.53 percent and temporary is 6.04 percent. Note how different that picture is from headcount, where full-time staff are only 56.25 percent of the people. Capacity and people are distributed differently, and confusing the two is how staffing plans go wrong.
The Standard Week Is a Choice, Not a Fact
The denominator does all the work in this calculation, and there is no universal value for it. Thirty-five, 37.5 and 40 hours are all common standards, and some sectors use annualised hours instead of weekly ones.
The same 214 part-time hours produce 5.35 FTE against a 40-hour week and 5.71 FTE against a 37.5-hour week — a difference of about 7 percent on that component. Across a large workforce that is easily a whole FTE or more, which matters when the figure is being used for a budget or to test a regulatory threshold. Pick the definition your contracts of employment actually use, write it down, and apply it to every group.
A second trap is annualising incorrectly. Weekly FTE assumes the pattern holds all year. If a group works only part of the year — a summer season, a term-time contract — a weekly calculation overstates their annual contribution substantially. The correct treatment is to convert their total annual hours to an annual full-time figure: someone working 600 hours in a year against a 2,080-hour full-time year is 0.29 FTE for the year, however close to full-time they looked during the weeks they were actually there. Enter seasonal staff on that annualised basis in the temporary field, scaled to a weekly equivalent, or run the calculation separately for the season.
Where Statutory Definitions Override Your Own
For internal planning you can define FTE however you like. For regulatory thresholds you cannot, and the definitions used in law are often deliberately different from the commonsense one.
The clearest example is the United States employer shared responsibility rules, where the Internal Revenue Service defines a full-time employee as someone averaging at least 30 hours of service a week or 130 hours a month, and then calculates full-time equivalents from everyone else by a specific method: combine the monthly hours of all non-full-time employees, counting no more than 120 hours for any one person, and divide the total by 120. The IRS guidance on determining if an employer is an applicable large employer works this through with an example: fifteen part-time employees at 60 hours a month contribute 900 hours, and 900 ÷ 120 = 7.5 full-time equivalents.
Notice three differences from the general formula. The threshold for full-time is 30 hours, not your standard week. The divisor is 120 monthly hours, not your standard week either. And individual hours are capped, so a part-timer working long hours in one month cannot contribute more than one equivalent. A general-purpose FTE figure and a statutory one can therefore differ substantially for the same workforce, and using the wrong one to test a threshold is a compliance error rather than a rounding difference. Similar divergences exist in grant funding rules, in headcount-based reporting obligations and in sector licensing, so always read the definition attached to the requirement rather than reusing your internal number.
What FTE Is Good For and What It Hides
FTE is the right unit for anything that scales with hours: payroll budgeting, capacity planning, revenue per FTE, cost per FTE and productivity comparisons over time. It is the only way to compare a department that runs on full-timers with one that runs on part-timers, and it is the correct denominator when you are dividing output by workforce.
It is the wrong unit for anything that scales with people. Every employee needs a contract, an induction, a manager's attention, a workstation, a licence for each system they use, and a place in the payroll run. Those costs attach to heads, not to hours, so a team of 32 people at 24.85 FTE carries meaningfully more administrative load than a team of 25 full-timers at the same 25 FTE. Management span is the same story: a manager with fourteen part-time reports is doing more coordination than one with seven full-time reports, even though the FTE is similar.
The FTE-per-head ratio is the number that makes this visible, and it is worth tracking over time. A falling ratio means the workforce is fragmenting into smaller contracts — often a deliberate and sensible response to variable demand, but one that raises per-head costs and turnover exposure. Reading it alongside the employee turnover rate calculator is instructive, because part-time and temporary populations frequently turn over faster than full-time ones. The Small Business Administration's guidance on managing your business covers the payroll and record-keeping foundations that make either measure reliable.
Arb Digital builds long-term online growth programmes that raise demand against the team you already have, rather than adding heads to chase it.
Web Growth Services Talk to Arb DigitalCommon Mistakes to Avoid
- Mixing standard weeks — using 37.5 hours for one department and 40 for another makes the total FTE figure meaningless.
- Annualising a seasonal pattern — a weekly FTE for staff who work three months a year overstates their annual contribution by a factor of four.
- Using an internal FTE for a statutory test — legal definitions set their own thresholds, divisors and caps, and rarely match an internal convention.
- Budgeting per-head costs on FTE — laptops, licences and onboarding scale with people, so an FTE-based budget understates them whenever part-time staff are numerous.
- Including overtime without deciding to — actual hours give a workload measure and contracted hours give a capacity measure; both are valid, mixing them is not.
Related Free Tools From Arb Digital
Pair this with the employee cost calculator to build the cost per FTE, the employee turnover rate calculator for stability of the workforce behind it, the hourly to salary calculator for converting part-time rates, the overtime pay calculator when actual hours exceed contracted ones, the prorated salary calculator for part-period pay, and the contractor vs employee calculator when capacity could be bought rather than hired. The full free online tools hub lists everything else.
Frequently Asked Questions
Divide the total hours worked by part-time and temporary staff by the standard full-time week, then add the number of full-time employees. The result expresses a mixed workforce as a number of full-time equivalents.
Headcount counts people regardless of hours. FTE counts capacity, so two half-time employees are two heads but one FTE. Costs that attach to people should be budgeted on headcount and costs that scale with hours on FTE.
Whatever your organisation defines as a full-time week — commonly 35, 37.5 or 40 hours. There is no universal figure, and some statutory rules set their own threshold that is lower than any of these.
Annualise them. Divide their total annual hours by the annual full-time hours rather than using a weekly figure, because a weekly calculation assumes the pattern continues all year and badly overstates a short season.
Only if you are measuring workload rather than capacity. Contracted hours give a planning figure, actual hours including overtime give a demand figure, and the important thing is applying one basis consistently.
Often not. Regulatory definitions set their own hour thresholds, divisors and per-person caps, so a statutory equivalent count can differ from an internal one for exactly the same workforce.
Not under a contracted-hours basis, because nobody can contribute more than one full-time equivalent. It can happen on an actual-hours basis if overtime is included, which is itself a useful signal that the team is running above its designed capacity.
This calculator performs arithmetic on figures you supply and is provided for general information only. It is not employment, tax or legal advice, and statutory definitions of full-time and full-time equivalent differ from the general formula used here — confirm any figure used for compliance, funding or reporting with a qualified professional.
