If the employees work a fixed number of days per week (of equal length), holiday entitlement should be calculated in days, rather than hours. For example, if the '13.5 hour' employee is working 3 days (of 4½ hours each) every week, then her holiday entitlement is 5.6 x 3 days = 16.8 days (including all 'enforced holidays', when the business is closed, such as public holidays).
The 'multiply by 5.6' rule holds true whenever employees work to a regular pattern (as illustrated above), except when someone works for more than 5 days per week. Under those circumstances, it has to be remembered that the statutory holiday entitlement is capped at 28 days.
For employees with an irregular work pattern, the calculation should be made on the basis of 12.07% of the hours worked). So someone working 30 hours will accrue 0.1207 x 30 hours of holiday entitlement ( = 3.621 hours).
If you need a calculator, see here:
http://www.businessli....l2=1073858926&r.s=tl
Chris