Prorated rent is the portion of the monthly rental rate calculated based on the number of days a tenant actually occupies a property during a partial month. This typically occurs when a tenant moves in or out on a day other than the first of the month.
Instead of paying for the full month when you only live there for a week, proration ensures you pay a fair amount based on your specific occupancy dates.
How to Calculate Prorated Rent
The standard method for calculating prorated rent involves determining the daily rental rate and multiplying it by the number of days the tenant holds possession of the property. The formula is as follows:
Step 1: Determine the Daily Rate. Divide the total monthly rent by the number of days in that specific month (e.g., 28, 30, or 31).
Step 2: Count Billable Days. Calculate the number of days from the move-in date to the end of the month (inclusive).
Step 3: Calculate Total. Multiply the Daily Rate by the Billable Days.
Example Calculation
If the monthly rent is $1,500 and you move in on September 20th:
September has 30 days.
Daily Rate = $1,500 / 30 = $50.00 per day.
Billable Days = September 20 to September 30 = 11 days (counting the 20th).
Prorated Rent = $50.00 x 11 = $550.00.
Why Does the Number of Days in the Month Matter?
Most landlords calculate the daily rate based on the actual number of days in the month the proration occurs. This means your daily rate in February (28 days) will be higher than in August (31 days). Some property managers may use a "Banker's Month" (flat 30 days) for all calculations to simplify accounting, so it is always best to check your lease agreement for the specific calculation method used.
function calculateProratedRent() {
// 1. Get Input Values
var rentInput = document.getElementById('prMonthlyRent').value;
var dateInput = document.getElementById('prMoveInDate').value;
var resultDiv = document.getElementById('prResult');
// 2. Validate Inputs
if (rentInput === "" || dateInput === "") {
alert("Please enter both the monthly rent and the move-in date.");
resultDiv.style.display = "none";
return;
}
var rent = parseFloat(rentInput);
if (rent < 0 || isNaN(rent)) {
alert("Please enter a valid positive rent amount.");
return;
}
// 3. Date Logic
// Create date object. Note: Input date is YYYY-MM-DD.
// We split it to avoid timezone issues ensuring we work with the exact date entered.
var dateParts = dateInput.split("-");
var year = parseInt(dateParts[0]);
var monthIndex = parseInt(dateParts[1]) – 1; // JS months are 0-11
var day = parseInt(dateParts[2]);
// Get total days in the specific month selected
// Using 0 as the day in the next month gives the last day of the current month
var daysInMonth = new Date(year, monthIndex + 1, 0).getDate();
// 4. Calculate Billable Days
// Logic: (Total Days – Move In Day) + 1.
// Example: Move in on the 20th of a 30 day month. 30 – 20 = 10 + 1 = 11 days.
var billableDays = daysInMonth – day + 1;
// Edge case: If date is invalid or calculated days are negative (shouldn't happen with date picker limits usually)
if (billableDays < 1) {
billableDays = 0;
}
// 5. Calculate Financials
var dailyRate = rent / daysInMonth;
var proratedAmount = dailyRate * billableDays;
// 6. Update UI
document.getElementById('prDaysInMonth').innerText = daysInMonth;
document.getElementById('prBillableDays').innerText = billableDays;
// Format as Currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
});
document.getElementById('prDailyRate').innerText = formatter.format(dailyRate);
document.getElementById('prFinalAmount').innerText = formatter.format(proratedAmount);
// Show Results
resultDiv.style.display = "block";
}