This calculator assumes rent is due on the 1st of the month.
Please enter a valid rent amount and date.
Total Days in Month:0
Days Occupied:0
Daily Rate:$0.00
Prorated Rent Due:$0.00
function calculateProratedRent() {
// Input Retrieval
var rentInput = document.getElementById('monthlyRent').value;
var dateInput = document.getElementById('moveInDate').value;
// Error Handling Elements
var errorDiv = document.getElementById('prcError');
var resultDiv = document.getElementById('prcResult');
// Validation
if (!rentInput || !dateInput || parseFloat(rentInput) <= 0) {
errorDiv.style.display = 'block';
resultDiv.style.display = 'none';
return;
}
// Logic
errorDiv.style.display = 'none';
var rentAmount = parseFloat(rentInput);
var moveInDate = new Date(dateInput);
// Avoid timezone issues by explicitly using UTC components or handling offset,
// but for simple date math on input type='date', basic methods usually suffice if we don't convert to UTC string.
// To be safe with 'date' inputs that return YYYY-MM-DD:
var year = moveInDate.getFullYear();
var month = moveInDate.getMonth(); // 0-indexed (Jan is 0)
var day = moveInDate.getDate(); // 1-31 (This gets day of month, but dependent on browser timezone parsing of the YYYY-MM-DD string)
// Correct parsing for YYYY-MM-DD to avoid timezone shifting logic
var dateParts = dateInput.split('-');
var year = parseInt(dateParts[0]);
var month = parseInt(dateParts[1]) – 1; // JS months are 0-11
var day = parseInt(dateParts[2]);
// 1. Calculate Total Days in that specific month
// Create a date for the 0th day of the next month, which gives the last day of current month
var daysInMonth = new Date(year, month + 1, 0).getDate();
// 2. Calculate Occupied Days
// If move in is on the 1st, occupied is all days. If move in is 15th, occupied includes the 15th.
// Formula: Total Days – Move In Day + 1
var occupiedDays = daysInMonth – day + 1;
// Edge case: If start date is invalid or calculated days < 0
if (occupiedDays < 0) {
occupiedDays = 0;
}
// 3. Calculate Daily Rate
var dailyRate = rentAmount / daysInMonth;
// 4. Calculate Total Prorated Amount
var totalProrated = dailyRate * occupiedDays;
// Display Results
document.getElementById('displayTotalDays').innerHTML = daysInMonth;
document.getElementById('displayOccupiedDays').innerHTML = occupiedDays;
document.getElementById('displayDailyRate').innerHTML = '$' + dailyRate.toFixed(2);
document.getElementById('displayTotalDue').innerHTML = '$' + totalProrated.toFixed(2);
resultDiv.style.display = 'block';
}
How to Calculate Prorated Rent
Moving into a new apartment or rental home rarely aligns perfectly with the first day of the month. When you move in on any day other than the 1st, landlords typically charge prorated rent. This ensures you only pay for the specific number of days you legally occupy the unit during that first partial month.
The Prorated Rent Formula
While some landlords use a flat 30-day month for calculations (known as a "banker's month"), the most accurate and common method uses the actual number of days in the specific month of your move-in. Our calculator uses this exact-day method:
Step 1: Determine the total number of days in the move-in month (e.g., September has 30 days, October has 31).
Step 2: Calculate the Daily Rental Rate by dividing the full monthly rent by the total days in that month.
Step 3: Count the Billable Days. This is the number of days from your move-in date to the end of the month (inclusive of the move-in day).
Step 4: Multiply the Daily Rental Rate by the Billable Days.
Calculation Example
Imagine you are leasing an apartment for $1,800 per month and your lease start date is August 18th.
You might notice the formula for days occupied is (Total Days - Start Day) + 1. This "plus one" is crucial because you must pay for the move-in day itself. If you moved in on the 30th of a 30-day month, simple subtraction (30-30) would equal zero, but you actually owe rent for 1 day.
Does this Apply to Move-Outs?
Yes, this calculator can also be used for move-outs. If your lease ends mid-month, you can enter your lease end date to determine how much rent you owe for that final partial month. However, always check your lease agreement, as some contracts require full month's rent regardless of when you vacate.