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Working time reference period

Your average night working time is normally calculated over a 17 week ‘reference period’ or however long a worker has been working for their employer if this is less then 17 weeks. This can be changed with agreement from your employer as part of a 'collective agreement'. This is an agreement reached between an employer and the trade union.

• Joining a trade union

Calculating simple working patterns

You average night time working hours is calculated by dividing the number of your normal hours worked in a reference period, by the number of days in the period. This does not include the number of rest days you are entitled to take.

Example

You are a night worker and work four 12-hour shifts each week:

1. Multiply the number of weeks in the reference period (17) with the number of hours you work each week: 17 x (4 x 12) = 816
2. In a 17 week period there are 119 days (17 x 7). You are entitled to take 17 weekly rest periods, therefore the number of days you could be asked to work is: 119 – 17 = 102 days
3. To calculate your daily average working time, your total hours is divided by the number of days you could be required to work: 816 divided by 102 = 8 hours

So you would have worked an average of eight hours a day, which is within the night work limit.

Calculating shift patterns

Sometimes shift working patterns are not as simple to work out or you may have taken leave.

Example

You are a night worker and work a ‘shift cycle’ of five days for 10 hour shifts, followed by three days of rest. The cycle starts at the beginning of the reference period. You also take two weeks leave and work six hours of overtime every five weeks (in the fifth, tenth and fifteenth weeks).

1. Calculate how many shift cycles the reference period covers by dividing the number of days in your reference period (17 weeks) with the number of days in your shift cycle: 17 x 7 = 119 then 119 / 8 = 15 cycles (rounded to the nearest number)
2. Next total the number of hours worked in the cycles:15 x (5 days x 10 hour shifts) = 750 hours
   
3. Then add the overtime 6 hours overtime x 3 weeks = 18 + 750 = 768 hours worked
4. Then subtract the weekly rest period you must take (rather than the amount your employer allows you) to calculate the number of days you could be asked to work: 119 – 17 = 102 days
5. Finally, divide the total hours worked by the number of days you could have worked: 768 / 102 = 7.53
   

So you would have worked an average of 7.53 hours a day, which is within the night work limit.

The annual leave taken does not affect the calculation of average working hours.

Do you have a problem with your night worker rights?

If you feel you are exceeding the night work limits:

• your employer may be in breach of contract
• the Health and Safety Executive could take action against your employer

If you think you are not receiving any other rights as a night worker you can:

• talk to your manager to try to sort matters quickly - be aware that your employer must keep records of the hours you have worked for them
• contact your trade union or health and safety representative (if you have one) for advice
• either approach matters informally or follow the contractual grievance procedure
  

• How to resolve a problem at work

• Breach of contract

• Health and safety at work

Where to get help

If you need further help the Pay and Work Rights helpline offers free and confidential advice on working hours.

• Pay and Work Rights Helpline

More useful links

• Advice for employers on working at night from Business Link Opens new window