Select "Full Year" unless the employee started or left part-way through the leave year.
Please enter valid positive numbers for all fields.
Total Holiday Entitlement0 Days
Full-Time Equivalent:28 Days
Pro Rata Percentage:0%
Equivalent in Hours:0 Hours
Understanding Pro Rata Holiday Entitlement
Calculating holiday entitlement for part-time workers or employees who start part-way through the year can be confusing. "Pro rata" is a Latin term meaning "in proportion," which in employment law ensures that part-time workers receive the same holiday benefits as full-time staff, adjusted relative to the hours they work.
How the Calculation Works
The standard formula for calculating pro rata holiday leave is based on the ratio of hours worked compared to a standard full-time week. The basic formula is:
(Hours Worked ÷ Full-Time Hours) × Full-Time Annual Leave = Pro Rata Entitlement
For example, if a full-time employee works 40 hours and gets 28 days of leave, someone working 20 hours (50% of the time) should logically receive 50% of the leave entitlement, which is 14 days.
Scenario 1: Part-Time Workers (Full Year)
If an employee works fewer hours than a full-time colleague but is employed for the entire year, their holiday is calculated purely on their weekly hours.
Full-time hours: 40 hours/week
Full-time leave: 28 days
Employee hours: 3 days a week (24 hours)
Calculation: (24 ÷ 40) × 28 = 16.8 days
Employers often round up (never down) to the nearest half-day to simplify management, though this is discretionary above the statutory minimum.
Scenario 2: Starting or Leaving Part-Way Through the Year
If an employee joins the company mid-year, their entitlement must be prorated further based on the number of months (or days) they are employed during that leave year. The calculator above includes a "Duration of Employment" field to handle this automatically.
For example, a full-time employee starting 6 months into the year would only be entitled to 50% of the annual allowance.
Bank Holidays
It is crucial to verify if the "Full-Time Annual Holiday Entitlement" input includes public/bank holidays. In many countries, the statutory minimum includes bank holidays. For part-time workers, bank holidays are usually calculated as part of the total pro rata allowance to avoid unfairness if their working days do not fall on bank holidays.
Legal Minimums
Ensure your inputs meet your local labor laws. In the UK, for example, the statutory minimum is 5.6 weeks (28 days for a 5-day week). Part-time workers are entitled to the same 5.6 weeks of their working week.
function calculateProRata() {
// Get input values
var ftDaysInput = document.getElementById('ftDays');
var ftHoursInput = document.getElementById('ftHours');
var ptHoursInput = document.getElementById('ptHours');
var monthsInput = document.getElementById('monthsEmployed');
var errorMsg = document.getElementById('error-message');
var resultArea = document.getElementById('result-area');
// Parse values
var ftDays = parseFloat(ftDaysInput.value);
var ftHours = parseFloat(ftHoursInput.value);
var ptHours = parseFloat(ptHoursInput.value);
var months = parseInt(monthsInput.value);
// Validation
if (isNaN(ftDays) || isNaN(ftHours) || isNaN(ptHours) || ftDays <= 0 || ftHours <= 0 || ptHours < 0) {
errorMsg.style.display = 'block';
resultArea.style.display = 'none';
return;
}
// Logic check: Part time hours shouldn't exceed full time hours (though technically possible for overtime, usually indicates error for this calc)
// We will allow it but just warn, strictly speaking logic remains valid.
errorMsg.style.display = 'none';
// 1. Calculate the Ratio
var workRatio = ptHours / ftHours;
// 2. Calculate Annual Pro Rata (before month adjustment)
var annualProRataDays = workRatio * ftDays;
// 3. Apply Month Adjustment (if not full year)
var monthFactor = months / 12;
var finalDays = annualProRataDays * monthFactor;
// 4. Calculate Hours Equivalent
// If they get X days, and a standard day is (ftHours / 5)? No, that assumes 5 day weeks.
// Better approach for hours: Total annual hours entitlement.
// Full time annual hours = ftDays * (ftHours / 5 [assuming 5 day week standard for 'Days' metric])
// A safer bet without assuming days per week is converting the final result based on the employee's average day length?
// Actually, the simplest accurate hour calc is: (Pro Rata Days) * (Hours per working day).
// Since we don't ask for days worked per week, we calculate total holiday HOURS entitlement directly from the ratio.
// Alternative accurate hour calc:
// Total Full Time Holiday Hours = (ftDays / 5) * ftHours. (Assuming standard 5 day basis for the 28 days quote).
// However, to be purely mathematical without assuming 5 days:
// We assume 'ftDays' implies standard working days.
// Let's calculate purely based on the ratio of the FT entitlement.
// Let's assume the "ftDays" is based on a standard working day length derived from ftHours.
// Average FT day length = ftHours / 5 (Standard assumption for 28 day statutory).
var averageFtDayLength = ftHours / 5;
var totalHolidayHours = finalDays * averageFtDayLength;
// If the user works irregular hours, the hours result is often more useful.
// Formatting results
// Round days to 2 decimal places usually, sometimes rounded up to nearest 0.5. Let's stick to 2 decimals for precision.
var displayDays = finalDays.toFixed(2);
var displayHours = totalHolidayHours.toFixed(2);
var displayPercent = (workRatio * 100).toFixed(1);
// Update DOM
document.getElementById('resultDays').innerHTML = displayDays + " Days";
document.getElementById('displayFtDays').innerHTML = ftDays + " Days";
document.getElementById('displayPercentage').innerHTML = displayPercent + "% (of Full Time)";
document.getElementById('resultHours').innerHTML = displayHours + " Hours";
// Show results
resultArea.style.display = 'block';
}