A holiday accrual calculator answers the question that comes up in the middle of the leave year rather than at the start: how much of this person's entitlement have they actually earned so far, and can they book the two weeks they have just asked for? Entitlement is a year's figure; accrual is how much of it has built up by today. For a regular-hours worker it runs with the calendar, so half the year gone is half the entitlement accrued. This page sets out how to calculate accrued holiday the way the free holiday leave calculator on this site does, and where an accrual rule belongs in a policy.
The accrued leave calculator runs with the leave year, in twelfths
Take the full-year entitlement and multiply by the months of the leave year that have passed, divided by twelve. A full-timer on 28 days is 14 days accrued at the half-year point; after nine days taken, that is 5 days accrued and still to book. Counting in days of the year rather than months is finer and the calculator accepts either. The accrued leave calculator on this site takes days a week, weeks of leave, months elapsed and days taken, and returns the accrued figure and the balance against it.
Booking ahead of accrual is a policy decision, not arithmetic
Nothing in law stops an employer letting someone take their whole year's leave in April, and many do. The accrual calculation exists so the employer can decide: a policy can say leave is bookable against the full-year entitlement, or only against what has accrued, or something between the two for the first year of employment. Whichever it is, it belongs in the written policy, and the policy template on this site has a line for it, so the answer is the same whoever is asked.
Accrual for irregular hours is a different calculation
For leave years beginning on or after 1 April 2024 an irregular-hours or part-year worker accrues holiday at 12.07 per cent of the hours actually worked in each pay period, not in twelfths of a year's figure. The calculator on this page is for regular patterns; the zero hours contract page on this site works the hours-based version, and the two must not be mixed in one record.
Why the accrued figure matters most for leavers
A leaver is owed pay for accrued holiday not taken, and can be asked to repay overtaken leave only if the contract allows it. The accrued figure at the leaving date is therefore the one number that turns into money, and it should come from the same calculation used all year rather than a fresh estimate on the last day. Keeping every request against the employee, which is what the paid wall chart on this site does, is what makes the leaving figure trustworthy.
Questions people ask about holiday accrual calculator
How do I calculate accrued holiday?
Full-year entitlement times the fraction of the leave year that has passed. 28 days at the half-year point is 14 days accrued; subtract days already taken for the balance available.
Can an employee take holiday before they have accrued it?
Yes, if the employer allows it; the law sets the entitlement, not the timing. State the rule in the policy so it is applied the same way to everyone.
Does accrual work the same for zero hours staff?
No. Irregular-hours and part-year workers accrue at 12.07 per cent of hours worked in each pay period for leave years starting on or after 1 April 2024, and that is a separate calculation on this site.
What happens to accrued holiday when someone leaves?
Accrued and untaken holiday is paid in the final pay. Overtaken holiday can be deducted only where the contract provides for it, so the accrual figure at the leaving date has to be right.