Standard Calendar Year (365 days)
Work Days Only (260 days)
Days Worked in Period:–
Proration Percentage:–
Accrued Vacation Days:–
Accrued Vacation Hours:–
How to Calculate Pro-Rated Vacation
Calculating pro-rated vacation is a crucial task for HR professionals, payroll managers, and employees who are starting or leaving a job mid-year. Pro-rating ensures that an employee receives a fair amount of vacation time proportional to the actual time they have worked during the accrual period.
Definition: Pro-rated vacation is the calculation of leave entitlement based on the percentage of the year an employee has been employed, rather than the full annual allowance.
When is Pro-Rating Used?
You typically need to calculate pro-rated vacation in the following scenarios:
New Hires: When an employee joins the company partway through the fiscal or calendar year.
Terminations/Resignations: When an employee leaves before the year ends, and you need to determine their final payout or remaining balance.
Status Changes: When an employee moves from part-time to full-time (or vice versa), affecting their accrual rate.
Leave of Absence: If an employee takes unpaid leave that does not count toward service time for accrual purposes.
The Calculation Formula
The standard formula for calculating pro-rated vacation involves two main steps: determining the proration factor and applying it to the annual entitlement.
Step 1: Determine the Time Worked
First, calculate the number of days the employee was active during the accrual period.
(End Date – Start Date) + 1 = Days Employed
Step 2: Calculate the Percentage
Divide the days employed by the total days in the year (typically 365 for a calendar year, or 260 for working days).
Formula:(Days Employed / Total Days in Year) × 100 = % Worked
Step 3: Apply to Entitlement
Multiply the percentage worked by the total annual vacation allowance.
Formula:% Worked × Annual Vacation Days = Pro-Rated Days
Example Calculation
Let's say an employee, Sarah, is entitled to 20 days of vacation per year. She starts her job on July 1st.
Days Employed: July 1st to December 31st is 184 days.
Ratio: 184 / 365 = 0.5041 (approx 50.4%).
Accrual: 0.5041 × 20 days = 10.08 days.
Most companies will round this number, often to the nearest half-day or whole day, resulting in 10 or 10.5 days of vacation for Sarah.
Accrual Bases: Calendar vs. Working Days
While the calendar year (365 days) is the most common denominator, some organizations prefer to use "working days" (typically 260 days a year, assuming a 5-day work week). It is vital to ensure that both the numerator (days worked) and the denominator (base year) use the same unit of measure to avoid calculation errors.
function calculateProratedVacation() {
// 1. Get DOM elements
var entitlementInput = document.getElementById('annualEntitlement');
var hoursPerDayInput = document.getElementById('hoursPerDay');
var startDateInput = document.getElementById('startDate');
var endDateInput = document.getElementById('endDate');
var accrualBaseSelect = document.getElementById('accrualBase');
var resultBox = document.getElementById('result');
// 2. Parse values
var annualEntitlement = parseFloat(entitlementInput.value);
var hoursPerDay = parseFloat(hoursPerDayInput.value);
var startDateStr = startDateInput.value;
var endDateStr = endDateInput.value;
var baseDays = parseFloat(accrualBaseSelect.value); // 365 or 260 usually
// 3. Validation
if (isNaN(annualEntitlement) || annualEntitlement < 0) {
alert("Please enter a valid annual vacation entitlement.");
return;
}
if (isNaN(hoursPerDay) || hoursPerDay <= 0) {
alert("Please enter valid work hours per day.");
return;
}
if (!startDateStr || !endDateStr) {
alert("Please select both a start date and an end date.");
return;
}
var start = new Date(startDateStr);
var end = new Date(endDateStr);
// Normalize time to midnight to ensure accurate day diff
start.setHours(0, 0, 0, 0);
end.setHours(0, 0, 0, 0);
if (end < start) {
alert("End date cannot be before start date.");
return;
}
// 4. Calculate Days Worked (Inclusive)
var timeDiff = Math.abs(end.getTime() – start.getTime());
var diffDays = Math.ceil(timeDiff / (1000 * 3600 * 24)) + 1; // +1 to make it inclusive of start date
// Handle "Calendar" base specifically to account for Leap Years if necessary,
// but for standard HR calc, 365 or 366 is used.
// If value is 'calendar', we determine 365 or 366 based on the year of the start date.
var totalYearDays = baseDays;
if (accrualBaseSelect.value === 'calendar') {
var year = start.getFullYear();
// Check for leap year
var isLeap = (year % 4 === 0 && year % 100 !== 0) || (year % 400 === 0);
totalYearDays = isLeap ? 366 : 365;
}
// If using 'Work Days Only' (260), we should strictly calculate only weekdays between dates
// However, for a simple pro-ration ratio, often companies just take (Calendar Days Employed / 365).
// If the user selected 260, they imply a numerator of working days.
// Let's implement a simple workday counter if base is 260.
var numeratorDays = diffDays;
if (totalYearDays === 260) {
// Count weekdays only
var weekdays = 0;
var curDate = new Date(start);
while (curDate 1) ratio = 1;
var accruedDays = annualEntitlement * ratio;
var accruedHours = accruedDays * hoursPerDay;
// 6. formatting
var percentageDisplay = (ratio * 100).toFixed(2) + '%';
var accruedDaysDisplay = accruedDays.toFixed(2);
var accruedHoursDisplay = accruedHours.toFixed(2);
// 7. Output results
document.getElementById('resDaysWorked').innerHTML = numeratorDays + " days";
document.getElementById('resPercentage').innerHTML = percentageDisplay;
document.getElementById('resAccruedDays').innerHTML = accruedDaysDisplay;
document.getElementById('resAccruedHours').innerHTML = accruedHoursDisplay;
resultBox.style.display = "block";
}