.rental-calculator-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
background: #fff;
padding: 20px;
border: 1px solid #e0e0e0;
border-radius: 8px;
box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}
.calc-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
@media (max-width: 600px) {
.calc-grid {
grid-template-columns: 1fr;
}
}
.input-group {
margin-bottom: 15px;
}
.input-group label {
display: block;
margin-bottom: 5px;
font-weight: 600;
color: #333;
font-size: 14px;
}
.input-group input, .input-group select {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.input-group input:focus {
border-color: #0073aa;
outline: none;
box-shadow: 0 0 0 2px rgba(0,115,170,0.2);
}
.section-title {
grid-column: 1 / -1;
font-size: 18px;
font-weight: bold;
margin-top: 10px;
margin-bottom: 10px;
color: #2c3e50;
border-bottom: 2px solid #f1f1f1;
padding-bottom: 5px;
}
.calc-btn {
grid-column: 1 / -1;
background-color: #0073aa;
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background 0.3s;
margin-top: 10px;
}
.calc-btn:hover {
background-color: #005177;
}
#calc-results {
display: none;
grid-column: 1 / -1;
background-color: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 6px;
padding: 20px;
margin-top: 20px;
}
.result-row {
display: flex;
justify-content: space-between;
padding: 10px 0;
border-bottom: 1px solid #e0e0e0;
}
.result-row:last-child {
border-bottom: none;
}
.result-label {
color: #555;
font-weight: 500;
}
.result-value {
font-weight: 700;
color: #333;
}
.positive-flow {
color: #27ae60;
}
.negative-flow {
color: #c0392b;
}
.big-result {
font-size: 24px;
margin-top: 10px;
padding-top: 10px;
border-top: 2px solid #ccc;
}
function calculateRentalCashFlow() {
// Get inputs
var price = parseFloat(document.getElementById('purchasePrice').value) || 0;
var down = parseFloat(document.getElementById('downPayment').value) || 0;
var rate = parseFloat(document.getElementById('interestRate').value) || 0;
var years = parseInt(document.getElementById('loanTerm').value) || 30;
var rent = parseFloat(document.getElementById('rentalIncome').value) || 0;
var taxAnnual = parseFloat(document.getElementById('propertyTax').value) || 0;
var insAnnual = parseFloat(document.getElementById('insurance').value) || 0;
var maintPercent = parseFloat(document.getElementById('maintenance').value) || 0;
var vacancyPercent = parseFloat(document.getElementById('vacancy').value) || 0;
var hoa = parseFloat(document.getElementById('hoa').value) || 0;
// Calculations
var loanAmount = price – down;
var monthlyRate = rate / 100 / 12;
var numPayments = years * 12;
// Mortgage Payment Formula
var mortgagePayment = 0;
if (monthlyRate > 0) {
mortgagePayment = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numPayments)) / (Math.pow(1 + monthlyRate, numPayments) – 1);
} else {
mortgagePayment = loanAmount / numPayments;
}
// Monthly Expenses
var taxMonthly = taxAnnual / 12;
var insMonthly = insAnnual / 12;
var maintMonthly = rent * (maintPercent / 100);
var vacancyMonthly = rent * (vacancyPercent / 100);
var totalMonthlyExpenses = taxMonthly + insMonthly + maintMonthly + vacancyMonthly + hoa;
var totalOutflow = mortgagePayment + totalMonthlyExpenses;
var monthlyCashFlow = rent – totalOutflow;
var annualCashFlow = monthlyCashFlow * 12;
// Cash on Cash Return
// (Annual Cash Flow / Total Cash Invested)
// Simplified: Total Cash Invested = Down Payment (Closing costs omitted for simplicity of this tool)
var cocReturn = 0;
if (down > 0) {
cocReturn = (annualCashFlow / down) * 100;
}
var expenseRatio = 0;
if (rent > 0) {
expenseRatio = (totalMonthlyExpenses / rent) * 100;
}
// Update UI
document.getElementById('res-mortgage').innerText = formatCurrency(mortgagePayment);
document.getElementById('res-expenses').innerText = formatCurrency(totalMonthlyExpenses);
document.getElementById('res-ratio').innerText = expenseRatio.toFixed(2) + '%';
var cfElement = document.getElementById('res-cashflow');
cfElement.innerText = formatCurrency(monthlyCashFlow);
var annualCfElement = document.getElementById('res-annual-cashflow');
annualCfElement.innerText = formatCurrency(annualCashFlow);
if (monthlyCashFlow >= 0) {
cfElement.className = "result-value positive-flow";
annualCfElement.className = "result-value positive-flow";
} else {
cfElement.className = "result-value negative-flow";
annualCfElement.className = "result-value negative-flow";
}
document.getElementById('res-coc').innerText = cocReturn.toFixed(2) + '%';
// Show results
document.getElementById('calc-results').style.display = 'block';
}
function formatCurrency(num) {
return '$' + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}
Property Purchase Details
30 Years
15 Years
10 Years
Income & Expenses
Monthly Mortgage (P&I):
$0.00
Total Monthly Expenses:
$0.00
Operating Expense Ratio:
0%
Net Monthly Cash Flow:
$0.00
Annual Cash Flow:
$0.00
Cash-on-Cash Return:
0.00%
Understanding Rental Property Cash Flow
Calculating cash flow is the single most important step in analyzing a potential real estate investment. Cash flow represents the net amount of money moving in or out of your business every month after all expenses and debt service (mortgage) have been paid.
Why Use a Rental Property Calculator?
Many new investors make the mistake of only subtracting the mortgage from the rent to determine profit. However, a true analysis must account for:
- Vacancy Rates: The percentage of time the property sits empty.
- Maintenance & Repairs: Setting aside 5-10% of rent for future repairs is industry standard.
- Capital Expenditures (CapEx): Major replacements like roofs or HVAC systems.
- Property Taxes & Insurance: These costs can rise annually and significantly impact margins.
How to Interpret Your Results
Once you have input your data into the calculator above, focus on these two key metrics:
1. Net Monthly Cash Flow
This is your "take-home" profit. Most investors look for a minimum of $100-$200 per door in net positive cash flow to consider a deal safe.
2. Cash-on-Cash Return (CoC)
This metric measures the annual return on the actual cash you invested (down payment). It compares your investment to other vehicles like the stock market. A CoC return of 8-12% is generally considered good in real estate, while anything above 15% is excellent.
Improving Negative Cash Flow
If the calculator shows a negative number (red), the property is a liability rather than an asset. To fix this, you can try negotiating a lower purchase price, increasing the down payment to lower the mortgage, or finding ways to increase the rental income (e.g., adding amenities or renovating).