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Pro Rata Holiday Calculator (UK)
Your Estimated Holiday Entitlement
0 Days
Understanding Pro Rata Holiday Entitlement in the UK
Calculating holiday entitlement for part-time workers or employees who start part-way through the year can be confusing. In the UK, every worker is entitled to statutory leave, and this guide explains how the pro rata calculation works legally and mathematically.
What is Statutory Leave?
Under UK law, almost all workers are entitled to 5.6 weeks of paid holiday a year. This is known as statutory leave entitlement or annual leave.
- For a full-time worker working 5 days a week, this equates to 28 days (5 days x 5.6 weeks).
- This 28-day cap typically includes the 8 annual bank holidays, though employers can choose to offer more contractually.
Note: Part-time workers are entitled to the same level of holiday as full-time workers, calculated on a pro-rata basis. Employers cannot treat part-time workers less favourably.
How is Pro Rata Calculated?
To calculate holiday for a part-time worker, you multiply the number of days they work each week by 5.6 (the statutory entitlement figure). However, if the company offers more than the statutory minimum (e.g., 33 days for full-time staff), the calculation adjusts based on the full-time equivalent days.
The standard formula used in our calculator is:
(Your Working Days ÷ Full-Time Working Days) × Full Annual Entitlement = Your Entitlement
Starting or Leaving Part-Way Through the Year
If you start a job part-way through the leave year, you are only entitled to the holiday accrued for the portion of the year you are employed. This is calculated using a monthly accrual system (often 1/12th of the annual entitlement per month) or a daily percentage for more precise payroll calculations.
Example Calculation
Imagine an employee named Sarah:
- Full-time entitlement: 28 days.
- Full-time week: 5 days.
- Sarah works: 3 days a week.
Sarah's calculation: (3 ÷ 5) × 28 = 16.8 days of holiday per year.
If Sarah only worked for 6 months of that year, her entitlement would be halved to 8.4 days.
Rounding Holiday Days
Statutory law states that holiday entitlement cannot be rounded down. While employers are not legally obliged to round up to the nearest full day, many do so for administrative simplicity. Our calculator provides the exact decimal figure to ensure accuracy.
function calculateHoliday() {
// 1. Get Input Values
var ftEntitlementInput = document.getElementById('ftEntitlement');
var fullTimeDaysInput = document.getElementById('fullTimeDays');
var yourDaysInput = document.getElementById('yourDays');
var monthsSelect = document.getElementById('employmentMonths');
var ftEntitlement = parseFloat(ftEntitlementInput.value);
var fullTimeDays = parseFloat(fullTimeDaysInput.value);
var yourDays = parseFloat(yourDaysInput.value);
var monthsEmployed = parseInt(monthsSelect.value);
// 2. Validation
if (isNaN(ftEntitlement) || ftEntitlement < 0) {
alert("Please enter a valid full-time entitlement (e.g., 28).");
return;
}
if (isNaN(fullTimeDays) || fullTimeDays <= 0) {
alert("Please enter valid full-time working days.");
return;
}
if (isNaN(yourDays) || yourDays < 0) {
alert("Please enter your valid working days.");
return;
}
// 3. Logic Calculation
// Step A: Calculate the Pro Rata ratio based on weekly work
var weeklyRatio = yourDays / fullTimeDays;
// Step B: Calculate annual entitlement if worked full year
var annualProRata = weeklyRatio * ftEntitlement;
// Step C: Adjust for months worked (Accrual)
var finalEntitlement = annualProRata * (monthsEmployed / 12);
// Statutory Cap Logic Check (UK Specific)
// Statutory max for 5-day week is 28 days.
// If someone works part time, it scales.
// We output the raw calculation but ensure it doesn't return NaN.
// 4. Formatting Results
// Rounding to 1 decimal place is standard for display, though exact allows for 2.
var displayValue = Math.round(finalEntitlement * 100) / 100;
// Prepare Breakdown Text
var breakdownHTML = "
Calculation Breakdown:";
breakdownHTML += "Full-Time Basis: " + fullTimeDays + " days/week = " + ftEntitlement + " days holiday.";
breakdownHTML += "Your Ratio: " + (weeklyRatio * 100).toFixed(1) + "% of a full-time role.";
if (monthsEmployed < 12) {
breakdownHTML += "Full Year Entitlement would be: " + annualProRata.toFixed(2) + " days.";
breakdownHTML += "Period Adjustment: You are employed for " + monthsEmployed + "/12 months.";
} else {
breakdownHTML += "Calculated for a full leave year (12 months).";
}
// 5. Update DOM
document.getElementById('totalHolidayDisplay').innerHTML = displayValue + " Days";
document.getElementById('breakdownDisplay').innerHTML = breakdownHTML;
var resultBox = document.getElementById('resultBox');
resultBox.style.display = 'block';
// Smooth scroll to result
resultBox.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}