The total number of holiday days a full-year employee receives.
Usually the end of your company's holiday year (often Dec 31st or Mar 31st).
Leave blank if calculating based solely on dates. Fill if calculating for part-time hours.
Only required if 'Hours Worked Per Week' is entered.
Days in Period:–
Pro-Rata Factor:–
Entitlement: 0 Days
function calculateProRatedLeave() {
// Get input values
var entitlementInput = document.getElementById("annualEntitlement").value;
var startDateInput = document.getElementById("startDate").value;
var endDateInput = document.getElementById("endDate").value;
var partTimeHoursInput = document.getElementById("hoursPerWeek").value;
var fullTimeHoursInput = document.getElementById("fullTimeHours").value;
// Element references for output
var resultBox = document.getElementById("resultBox");
var daysInPeriodDisplay = document.getElementById("daysInPeriodResult");
var percentageDisplay = document.getElementById("percentageResult");
var finalResultDisplay = document.getElementById("finalLeaveResult");
// Validation
if (!entitlementInput || !startDateInput || !endDateInput) {
alert("Please fill in the Annual Entitlement, Start Date, and End Date.");
return;
}
var entitlement = parseFloat(entitlementInput);
var start = new Date(startDateInput);
var end = new Date(endDateInput);
// Check date validity
if (end 0 && fullTime > 0) {
hourRatio = partTime / fullTime;
}
}
// Final Calculation
// Formula: (Days Employed / Days in Year) * (Hours Worked / Full Time Hours) * Annual Entitlement
var calculatedLeave = dateRatio * hourRatio * entitlement;
// Rounding (Standard practice is often nearest 0.5 or 1 decimal, using 1 decimal for precision)
var roundedLeave = Math.round(calculatedLeave * 10) / 10;
var percentage = (dateRatio * hourRatio * 100).toFixed(1);
// Display Results
daysInPeriodDisplay.innerText = diffDays + " days";
percentageDisplay.innerText = percentage + "% of full year/time";
finalResultDisplay.innerText = roundedLeave;
resultBox.style.display = "block";
}
How to Calculate Pro-Rated Leave
Calculating pro-rated leave (holiday entitlement) is essential for ensuring that employees who join a company part-way through the year, or who leave before the year ends, receive their fair share of statutory or contractual time off. This guide and calculator will help you determine the exact number of days owed.
What is Pro-Rated Leave?
The term "pro-rata" means "in proportion." When applied to annual leave, it refers to adjusting the total holiday allowance based on the amount of time an employee has actually worked during the leave year. This applies to:
New Starters: Employees joining after the start of the holiday year.
Leavers: Employees resigning or being dismissed before the holiday year ends.
Part-Time Workers: Employees working fewer hours than a standard full-time equivalent.
The Calculation Formula
The standard formula for calculating pro-rated holiday entitlement for a partial year is:
(Days Employed ÷ Days in Year) × Annual Entitlement = Pro-Rated Leave
If the employee is also working part-time hours compared to a full-time employee, you must apply a second ratio:
Let's look at a practical example using the logic from the calculator above:
Annual Entitlement: 28 days (Standard statutory minimum in the UK including bank holidays).
Scenario: Jane joins the company on July 1st.
Leave Year Ends: December 31st.
Step 1: Calculate Days Employed.
From July 1st to December 31st is 184 days.
Step 2: Determine Proportion of Year.
184 days ÷ 365 days = 0.504 (roughly 50.4% of the year).
Step 3: Apply to Entitlement.
0.504 × 28 days = 14.11 days.
Most employers will round this figure up to the nearest half-day or full day, giving Jane roughly 14 or 14.5 days of leave for the remainder of the year.
Handling Leap Years
In a leap year, the total number of days is 366. While the difference in calculation is minimal, strict compliance often requires using 366 as the divisor if the period of employment falls within a leap year. Our calculator automatically detects the year of your start date to adjust for this.
Part-Time Adjustments
If an employee works part-time, their leave is usually calculated in hours to ensure accuracy. For example, if a full-time employee (40 hours) gets 20 days off, a part-time employee working 20 hours a week would technically get 10 days off, or the equivalent number of hours (e.g., if days are 8 hours long, they get 80 hours of leave).