Standard statutory leave is often 28 days (including bank holidays).
Enter 12 for a full year, or less if starting/leaving partway.
Total Holiday Entitlement
0 Days
function calculateProRata() {
// Get inputs
var ftEntitlement = parseFloat(document.getElementById('fullTimeEntitlement').value);
var ftHours = parseFloat(document.getElementById('fullTimeHours').value);
var ptHours = parseFloat(document.getElementById('partTimeHours').value);
var months = parseFloat(document.getElementById('monthsEmployed').value);
var resultBox = document.getElementById('resultBox');
var resultDisplay = document.getElementById('finalEntitlement');
var breakdownDisplay = document.getElementById('calculationBreakdown');
// Validation
if (isNaN(ftEntitlement) || isNaN(ftHours) || isNaN(ptHours) || isNaN(months)) {
alert("Please enter valid numbers in all fields.");
return;
}
if (ftHours <= 0) {
alert("Full-time hours must be greater than 0.");
return;
}
if (months 12) {
alert("Months employed must be between 0 and 12.");
return;
}
// Calculation Logic
// 1. Calculate the pro-rata ratio based on hours (Part Time / Full Time)
var hoursRatio = ptHours / ftHours;
// 2. Calculate the portion of the year worked (Months / 12)
var timeRatio = months / 12;
// 3. Final Calculation
var entitlement = ftEntitlement * hoursRatio * timeRatio;
// Formatting
// Usually rounded to 1 or 2 decimal places, or rounded up to nearest half day.
// We will display 2 decimal places for accuracy.
var formattedResult = entitlement.toFixed(2);
// Show Results
resultBox.style.display = "block";
resultDisplay.innerHTML = formattedResult + " Days";
breakdownDisplay.innerHTML =
"Based on working " + ptHours + " hours out of a standard " + ftHours + " hour week (" + (hoursRatio * 100).toFixed(1) + "% FTE) " +
"over " + months + " months.";
}
How to Calculate Holiday Pro Rata
Calculating holiday pro rata is an essential task for employers and HR professionals managing part-time staff or employees who start or leave partway through the leave year. "Pro rata" simply means "in proportion," ensuring that employees receive a fair amount of holiday leave based on the actual time they work compared to a full-time equivalent.
This guide explains the mathematics behind the calculator above and how to handle various employment scenarios.
The Pro Rata Holiday Formula
To calculate holiday entitlement for a part-time worker who works the same number of hours every week, the standard formula is straightforward. You are essentially calculating the percentage of a full-time week they work, and applying that same percentage to the full-time holiday allowance.
The Basic Formula:
(Hours Worked ÷ Full-Time Hours) × Full-Time Annual Holiday Entitlement = Pro Rata Entitlement
Step-by-Step Calculation
Determine Full-Time Entitlement: Identify the total annual leave a full-time employee receives (e.g., 28 days statutory in the UK).
Calculate the Ratio: Divide the employee's weekly hours by the company's standard full-time weekly hours.
Multiply: Multiply this ratio by the full-time entitlement.
Adjust for Time (If applicable): If the employee is only employed for part of the year, multiply the result by (Months Worked ÷ 12).
Practical Examples
Example 1: Part-Time Employee (Full Year)
Imagine an employee named Sarah. The company's full-time staff work 40 hours a week and get 28 days of holiday.
Sarah works 20 hours per week.
Calculation: (20 ÷ 40) = 0.5 (or 50%).
0.5 × 28 days = 14 days of holiday.
Example 2: Condensed Hours
John works full-time hours (37.5) but compresses them into 4 days instead of 5. His holiday entitlement in hours remains the same as a 5-day worker, but if calculated in days, it must be adjusted so he doesn't get more time off than colleagues.
Ideally, for condensed hours or irregular shifts, it is best to calculate holiday entitlement in hours rather than days to ensure accuracy.
Example 3: Starting Partway Through the Year
Mark joins a company on July 1st. The leave year runs January to December. He works full-time (40 hours).
Full annual entitlement: 28 days.
He works for 6 months of the year (July to Dec).
Calculation: (6 ÷ 12) × 28 = 14 days.
Common Questions on Holiday Pro Rata
How do Bank Holidays fit in?
In many jurisdictions, statutory leave entitlements (like the UK's 5.6 weeks or 28 days) include public/bank holidays. When calculating pro rata for part-time workers, it is safest to give them a pro-rata allowance of the total days (inclusive of bank holidays). If a bank holiday falls on a day they do not work, they do not get an extra day off, but their pro-rata pot of hours/days remains available for them to book other times.
Rounding Up
Legally, you cannot round down holiday entitlement. If a calculation results in a fraction (e.g., 14.3 days), you typically round up to the nearest half-day or keep the decimal to be taken in hours, depending on company policy. You should never round down, as this would deny statutory rights.
What about irregular hours / zero-hours contracts?
For employees with no fixed hours, a common method (specifically in the UK) was the "12.07%" rule, where holiday was accrued at 12.07% of hours worked. However, recent legal rulings (Harper Trust v Brazel) have complicated this, suggesting that 5.6 weeks' holiday must be paid even if fewer weeks are worked. Always check the latest local employment law for zero-hours calculations.