The three most important are:
- Contracted weekly hours = the number of hours you are employed to work
- Shift span = the total time from the start of a shift to the finish
- Paid shift length = the working time after unpaid breaks are removed
For example:
- Contracted hours: 37.5 hours per week
- Shift: 07:00–19:00
- Shift span: 12 hours
- Unpaid break: 30 minutes
- Paid shift length: 11h 30m
What are NHS contracted hours?
Your contracted hours are the number of hours you are employed to work.
For a standard full-time Agenda for Change working pattern, the usual reference is 37.5 hours per week.
That does not necessarily mean you must work 5 × 7.5-hour shifts. It simply describes the full-time weekly contractual hours.
The way those hours are arranged can depend on your rota.
For example, one employee may work five shorter shifts, while another may work longer shifts across a repeating rota. Both can still have 37.5 contracted hours per week.
UK nations: 37.5 hours is the standard full-time week in England. NHS Scotland’s standard full-time week reduced to 36 hours from 1 April 2026, so the full-time reference and WTE figures differ there.
What is a shift length?
A shift length describes an individual period of work.
For example, 07:00–19:00 has a total start-to-finish span of 12 hours.
But this does not automatically mean you are being paid for 12 hours.
If the shift includes an unpaid break, the paid shift length will be shorter.
This is why it helps to separate shift span from paid shift length.
Shift span vs paid shift length
Suppose your shift is 07:00–19:00. From start to finish, that is 12 hours.
Now suppose you have a 30-minute unpaid break. Your paid shift length becomes 11h 30m.
So the three figures might be:
- Shift start: 07:00
- Shift finish: 19:00
- Shift span: 12h
- Unpaid break: 30m
- Paid shift length: 11h 30m
For many calculations, including working out how much annual leave a particular shift represents, the paid shift length is the more useful figure.
Why 37.5 contracted hours does not mean five 7.5-hour shifts
A 37.5-hour full-time contract can be worked in different ways.
The simplest pattern would be:
5 × 7.5 hours = 37.5 hours
But NHS rotas do not always use five equal working days.
A member of staff may instead work a mixture of:
- long shifts
- shorter shifts
- weekdays
- weekends
- different hours from one week to another
The contract describes the total working-hours commitment. The rota describes how those hours are actually arranged. Those are two different things.
How long shifts fit into a 37.5-hour contract
Long shifts do not necessarily have to add up to exactly 37.5 hours in every individual week.
Hours can be arranged over a rota cycle so that the average matches the contracted requirement.
For example:
- Week 1 paid hours: 34.5h
- Week 2 paid hours: 40.5h
Total over two weeks:
34.5 + 40.5 = 75 hours
Average:
75 ÷ 2 = 37.5 hours per week
So one week is below 37.5 hours and the next is above it. Across the two-week period, the average is 37.5 hours.
This is why looking at one isolated rota week does not always tell you whether the contracted-hours total is correct.
What does averaging over a rota period mean?
A rota may be designed over a longer period rather than treating every week as identical.
For example, over four weeks a full-time employee would have a reference total of:
37.5 × 4 = 150 hours
Those 150 hours could be distributed unevenly. For example:
- Week 1: 34.5h
- Week 2: 40.5h
- Week 3: 34.5h
- Week 4: 40.5h
Total: 150 hours. Average: 37.5 hours per week.
The exact rota arrangement depends on the role, department and local working arrangements, but the important principle is that contracted weekly hours and individual weekly rota totals are not always identical.
Part-time NHS contracted hours
Part-time staff work fewer contracted hours than the standard full-time 37.5-hour week.
For example:
| Contracted weekly hours | Whole-time equivalent |
|---|---|
| 37.5h | 1.0 WTE |
| 30h | 0.8 WTE |
| 22.5h | 0.6 WTE |
| 18.75h | 0.5 WTE |
The WTE figure shows the proportion of full-time hours worked.
30 ÷ 37.5 = 0.8 WTE
22.5 ÷ 37.5 = 0.6 WTE
However, contracted weekly hours do not tell you what the individual shifts look like.
Same contracted hours, different shift patterns
Two employees can have exactly the same contracted weekly hours while working very different shifts.
For example, both employees work 22.5 hours per week.
Employee A
- Monday: 7h 30m
- Tuesday: 7h 30m
- Wednesday: 7h 30m
- Total: 22h 30m
Employee B
- Monday: 10h
- Tuesday: 7h 30m
- Wednesday: 5h
- Total: 22h 30m
Both employees have the same contracted weekly hours. But their individual shift lengths are different.
That can matter when annual leave is deducted.
Contracted hours vs rota hours
Your contracted hours describe the overall working-hours commitment.
Your rota hours describe what you are actually scheduled to work over a particular period.
They may not always look identical.
For example, your contract could state 37.5 hours per week, while one rota week shows 40.5 hours and another shows 34.5 hours.
That does not necessarily mean your contractual hours have changed. The rota may be designed to average out over a longer period.
If your rota totals regularly do not appear to match your contract, check the relevant rota period rather than comparing only one week.
Which number should you use?
Different calculations need different hour figures.
To calculate WTE
Use contracted weekly hours.
30 ÷ 37.5 = 0.8 WTE
To calculate the length of a specific shift
Use: Finish time − start time − unpaid breaks
07:00–19:00 = 12h, minus a 30m unpaid break = 11h 30m paid
To convert annual leave hours into shifts
Use paid shift length.
92 hours leave ÷ 11.5-hour paid shift = 8 shifts
To compare with the standard full-time NHS reference
Use 37.5 contracted hours per week.
Knowing which number to use prevents several common calculation mistakes.
How contracted hours affect annual leave
Your contracted weekly hours are important when calculating annual leave entitlement.
For part-time staff, contracted hours can be used to calculate WTE.
22.5 ÷ 37.5 = 0.6 WTE
The full-time annual leave entitlement can then be adjusted to that proportion.
For a detailed calculation, see NHS Part-Time Annual Leave in Hours and How to Work Out NHS Annual Leave in Hours.
How shift length affects annual leave usage
Once your annual leave entitlement is known, your individual shift lengths can affect how much leave is used.
For example, suppose your rota includes:
- Monday: 10h paid
- Tuesday: 7h 30m paid
- Wednesday: 5h paid
Taking Monday as annual leave may use 10 hours. Taking Wednesday may use 5 hours.
Your contracted weekly hours help determine how much annual leave you receive. Your paid shift length helps determine how that leave is used.
This is one of the most important distinctions to understand.
Why unpaid breaks matter
An unpaid break can change the paid length of a shift.
For example:
- Shift span: 12 hours
- Unpaid break: 30 minutes
- Paid shift: 11h 30m
If you mistakenly use 12 hours instead of 11h 30m, calculations involving shifts or leave may be incorrect.
Always check whether the break is paid or unpaid before deciding which shift length to use.
Common mistakes with NHS contracted hours and shifts
Assuming 37.5 hours means five identical working days
It does not necessarily. 37.5 hours is the standard full-time weekly reference, not a required five-day shift pattern.
Using shift span instead of paid shift length
A 12-hour start-to-finish period may contain unpaid breaks. The paid shift could be shorter.
Treating contracted hours and rota hours as the same thing
A rota may vary from week to week while still averaging to the contractual total.
Assuming every week must equal exactly 37.5 hours
Depending on the rota arrangement, some weeks may be higher and others lower.
Using shift length to calculate WTE
WTE is based on contracted weekly hours, not the length of one individual shift.
Using contracted weekly hours to calculate one shift
A 37.5-hour contract does not tell you how long a particular shift is. You need the actual shift start, finish and break information.
Forgetting unpaid breaks
Breaks can change the paid shift length significantly.