Include bank holidays if they are part of the standard contract.
Use 12 for a full year, or less if you started/are leaving mid-year.
Your Pro Rata Entitlement
How to Calculate Pro Rata Holiday Entitlement
Pro rata holiday is the amount of leave an employee is entitled to if they work fewer hours than a full-time employee, or if they only work part of a year. The principle is to ensure that part-time workers receive the same proportion of leave relative to the hours they work as their full-time colleagues.
The Formula
(Actual Weekly Hours ÷ Full-time Weekly Hours) × Full-time Day Entitlement = Pro Rata Days
Example Calculation
If a full-time employee gets 28 days of holiday for working 40 hours a week, and you work 20 hours a week, the calculation is:
Pro Rata Ratio: 20 / 40 = 0.5
Entitlement: 0.5 × 28 = 14 days per year
Mid-Year Starters and Leavers
If you start or leave a job partway through the holiday year, your entitlement is further adjusted by the number of months you are employed. For example, if you are entitled to 20 days per year but only work 6 months of the year, you would receive 10 days.
Legal Minimums
In many jurisdictions, there is a statutory minimum. For example, in the UK, the statutory minimum is 5.6 weeks of paid holiday. For a full-time worker (5 days a week), this equals 28 days. Part-time workers are entitled to the same 5.6 weeks, but proportionate to their working week.
function calculateProRata() {
var ftEntitlement = parseFloat(document.getElementById('ftEntitlement').value);
var ptHours = parseFloat(document.getElementById('ptHours').value);
var ftHours = parseFloat(document.getElementById('ftHours').value);
var monthsWorked = parseFloat(document.getElementById('monthsWorked').value);
var resultArea = document.getElementById('resultArea');
var totalDaysDisplay = document.getElementById('totalDays');
var totalHoursDisplay = document.getElementById('totalHours');
if (isNaN(ftEntitlement) || isNaN(ptHours) || isNaN(ftHours) || isNaN(monthsWorked)) {
alert("Please enter valid numbers in all fields.");
return;
}
if (ftHours <= 0) {
alert("Full-time hours must be greater than zero.");
return;
}
// Calculation Logic
// Step 1: Ratio of hours
var hourRatio = ptHours / ftHours;
// Step 2: Annual pro-rata days
var annualProRataDays = ftEntitlement * hourRatio;
// Step 3: Proportion of the year worked
var yearRatio = monthsWorked / 12;
// Final result
var finalEntitlementDays = annualProRataDays * yearRatio;
// Convert to hours (assuming an 8 hour day for visual reference, but better to use the ratio)
// Most HR systems calculate the specific hour total for accuracy
var averageDayLength = ftHours / 5; // Assuming 5-day standard for day conversion
var finalEntitlementHours = finalEntitlementDays * averageDayLength;
totalDaysDisplay.innerHTML = finalEntitlementDays.toFixed(2) + " Days";
totalHoursDisplay.innerHTML = "Equivalent to approx. " + finalEntitlementHours.toFixed(1) + " hours per year";
resultArea.style.display = "block";
resultArea.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}