Standard statutory leave is often 28 days (including bank holidays).
Enter 12 if you are employed for the full year.
Your Calculated Holiday
0 Days
function calculateHoliday() {
var fullEntitlement = parseFloat(document.getElementById('fullTimeEntitlement').value);
var standardDays = parseFloat(document.getElementById('standardDaysPerWeek').value);
var yourDays = parseFloat(document.getElementById('yourDaysPerWeek').value);
var months = parseFloat(document.getElementById('monthsWorked').value);
if (isNaN(fullEntitlement) || isNaN(standardDays) || isNaN(yourDays) || isNaN(months)) {
alert("Please enter valid numbers in all fields.");
return;
}
if (standardDays <= 0 || months <= 0) {
alert("Standard days and months worked must be greater than zero.");
return;
}
// Calculation Logic:
// 1. Calculate the pro-rata ratio based on days worked vs standard days
var workRatio = yourDays / standardDays;
// 2. Apply ratio to full entitlement
var annualProRata = fullEntitlement * workRatio;
// 3. Adjust for part-year employment (if not working 12 months)
var monthRatio = months / 12;
var finalEntitlement = annualProRata * monthRatio;
// Rounding to nearest half day is common practice in HR, but let's show 2 decimals
var finalEntitlementRounded = finalEntitlement.toFixed(1);
document.getElementById('resultValue').innerText = finalEntitlementRounded + " Days";
var explanation = "Based on working " + yourDays + " days a week (compared to a standard " + standardDays + "-day week) for " + months + " months of the year.";
document.getElementById('resultExplanation').innerHTML = explanation;
document.getElementById('resultBox').style.display = "block";
}
Understanding Holiday Pro Rata Calculations
Calculating holiday entitlement for part-time staff or employees starting partway through a year can be confusing. The term "pro rata" essentially means "in proportion." If you work less than a full-time schedule, your holiday allowance is calculated in proportion to the amount of time you work.
How the Calculation Works
The standard formula used by most HR departments and statutory guidance follows a simple logic: compare your working time to a full-time equivalent and apply that percentage to the full holiday allowance.
The formula is generally:
(Your Days per Week ÷ Full-Time Days) × Full Annual Holiday Entitlement
If you join or leave a company partway through the leave year, a further calculation is required to pro-rate the entitlement based on the number of months employed.
Key Definitions
Full-Time Entitlement: The total number of days a full-time employee receives per year. In the UK, the statutory minimum is 28 days (5.6 weeks), but many companies offer more.
Standard Work Week: Usually 5 days (Monday to Friday), though this can vary by industry.
Leave Year: The 12-month period over which holiday accrues. This often runs from January to December or April to March.
Example Scenarios
Scenario 1: Part-Time Worker (Full Year)
Jane works 3 days a week. The company's full-time staff work 5 days a week and get 28 days of holiday.
Calculation: (3 ÷ 5) × 28 = 16.8 days.
Jane is entitled to 16.8 days of leave for the year.
Scenario 2: Full-Time Worker (Part Year)
Mark starts a new full-time job (5 days a week) but only works for 6 months of the leave year.
Calculation: 28 days × (6 ÷ 12) = 14 days.
Mark gets 14 days to use during his 6 months of employment.
Rounding Holiday Entitlement
When calculations result in a fraction of a day (e.g., 16.8 days), employers cannot round down statutory leave entitlements. Typically, this is rounded up to the nearest half-day or whole day, or the exact figure is managed in hours, depending on company policy.
Why Use a Calculator?
Manual calculations often lead to errors, particularly when dealing with non-standard work weeks. Using a digital tool ensures that both the part-time ratio and the part-year duration are factored in accurately, ensuring fairness for both the employer and the employee.