FTE Capacity Planning With Public Holidays: A Practical Method
A team of 5.4 FTE does not have 5.4 times the working days of one person in every month. Holidays that land on part-timers' working days and fixed leave make the real number lumpier.
A delivery manager sizes next month's work from headcount: six people, 5.4 FTE, roughly 20 working days, so about 108 person-days. The real figure for May 2027 in England turns out to be 93 person-days. The gap comes from two Monday bank holidays, a part-timer who only works the start of the week, and leave already in the diary.
Full-time equivalent is a useful way to describe a team, but it is a poor way to calculate monthly capacity unless you apply it to the actual calendar.
Why FTE alone is not enough
FTE expresses contracted time as a fraction of a full-time week. Someone working three days out of five is 0.6 FTE. Multiplying FTE by a month's working days assumes that holidays and leave fall evenly across everyone's working pattern. They do not.
- Public holidays fall on specific weekdays. Someone who never works Mondays is unaffected by a Monday holiday; someone who works Monday to Wednesday is hit hard by one.
- Leave is booked in blocks, by individuals, and is often concentrated in particular months.
- Months have different numbers of weekdays, and the number of each weekday in a month (four or five Mondays, for example) varies.
Worked example: a six-person team, May 2027, England
May 2027 starts on a Saturday. It has 21 weekdays. Two bank holidays fall on Mondays: the early May bank holiday on 3 May and the spring bank holiday on 31 May. That leaves 19 working days for a Monday-to-Friday worker. See the UK holiday calendar for the dates.
The team:
- Four full-time members (Monday to Friday).
- One member at 0.8 FTE, working Monday to Thursday.
- One member at 0.6 FTE, working Monday to Wednesday.
Total FTE: 4 + 0.8 + 0.6 = 5.4.
Step 1: Count each person's working days
May 2027 contains five Mondays, four Tuesdays, four Wednesdays and four Thursdays (and four Fridays). Two of the Mondays are bank holidays.
| Member | Pattern | Pattern days in May | Holidays on pattern | Working days |
|---|---|---|---|---|
| Full-time × 4 | Mon–Fri | 21 each | 2 | 19 each (76 total) |
| 0.8 FTE | Mon–Thu | 17 | 2 | 15 |
| 0.6 FTE | Mon–Wed | 13 | 2 | 11 |
| Total | 102 |
The FTE shortcut, 5.4 × 19 working days, gives 102.6. That is close here, but note why: the 0.6 FTE member has 11 working days, which is 0.58 of a full-timer's 19, because both holidays fell on their working days. In a month with Friday holidays, they would come out ahead of their FTE share. Over a year, these effects can add up, which is why some employers pro-rate holiday entitlement for part-timers rather than simply giving them whichever holidays fall on their days. That is a policy question; check your contracts.
Step 2: Subtract booked leave
Suppose leave already booked for May is:
- One full-timer: a week off, 5 working days.
- Another full-timer: 3 days.
- The 0.8 FTE member: 1 day.
102 − 9 = 93 person-days available.
Step 3: Apply a planning factor if you use one
Not all available time goes on planned project work. Meetings, support, reviews and unplanned absence take a share. Many teams apply a planning factor, but the right value is specific to the team. Derive it from your own past data (planned versus actual delivered effort) and label it clearly. For illustration only, an 80 per cent factor would give 93 × 0.8 = 74.4 person-days of plannable work.
Compare that with the opening estimate of 108. Planning to the larger figure would have overcommitted the team by nearly half.
Teams across several countries
Distributed teams add a calendar per location. In the same month, a colleague in Germany has Labour Day on Saturday 1 May (no substitute), Ascension Day on Thursday 6 May and Whit Monday on 17 May. A colleague in the United States has Memorial Day on Monday 31 May. Each person's working days must be counted against their own calendar.
For work that needs people together, such as reviews, pairing or releases, look not only at total capacity but at the days when the people involved are all working. The team overlap tool shows shared working days and hours across locations, which is often the real constraint.
Looking ahead more than a month
For quarterly or annual plans, run the same count month by month rather than once for the whole period. Holidays and leave are uneven, and the months that are short for one person may be normal for another. A simple grid with one row per person and one column per month, filled with working days after holidays and booked leave, makes the lumpy months obvious. It also shows when a single absence, such as one specialist's long leave, removes a capability rather than just a share of capacity.
Common mistakes
- Using a fixed 20 or 21 days per month. Actual working days in England in 2027 range from 19 (May) to 22 (several months).
- Pro-rating holidays by FTE. Holidays hit specific weekdays; count them against each pattern.
- Ignoring leave until it is taken. Use booked leave plus a provision for leave typically taken in that month.
- Treating the planning factor as universal. Use your own history.
- One calendar for a distributed team. Use each member's location.
A monthly capacity routine
- List each team member with their working pattern and location.
- Count their working days for the month on their own calendar, using the business days calculator or the relevant country page.
- Subtract booked leave and known commitments such as training.
- Apply your team's own planning factor, if you use one, and note its source.
- Check overlap days for any work that needs several people at once.
- Revisit mid-month when leave or sickness changes the picture.
