.rp-calculator-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 20px;
border: 1px solid #e0e0e0;
border-radius: 8px;
background-color: #f9f9f9;
}
.rp-calc-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
@media (max-width: 600px) {
.rp-calc-grid {
grid-template-columns: 1fr;
}
}
.rp-input-group {
margin-bottom: 15px;
}
.rp-input-group label {
display: block;
font-weight: 600;
margin-bottom: 5px;
font-size: 14px;
color: #333;
}
.rp-input-group input {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.rp-section-title {
grid-column: 1 / -1;
font-size: 18px;
font-weight: bold;
margin-top: 10px;
margin-bottom: 10px;
color: #2c3e50;
border-bottom: 2px solid #ddd;
padding-bottom: 5px;
}
.rp-btn {
grid-column: 1 / -1;
background-color: #27ae60;
color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background-color 0.3s;
margin-top: 10px;
}
.rp-btn:hover {
background-color: #219150;
}
.rp-results {
grid-column: 1 / -1;
background-color: #fff;
padding: 20px;
border-radius: 6px;
border: 1px solid #ddd;
margin-top: 20px;
display: none;
}
.rp-result-row {
display: flex;
justify-content: space-between;
padding: 10px 0;
border-bottom: 1px solid #eee;
font-size: 16px;
}
.rp-result-row:last-child {
border-bottom: none;
}
.rp-result-label {
color: #555;
}
.rp-result-value {
font-weight: bold;
color: #2c3e50;
}
.rp-highlight {
color: #27ae60;
font-size: 20px;
}
.rp-article {
max-width: 800px;
margin: 40px auto;
line-height: 1.6;
color: #333;
}
.rp-article h2 {
color: #2c3e50;
margin-top: 30px;
}
.rp-article h3 {
color: #34495e;
margin-top: 20px;
}
.rp-article ul {
margin-bottom: 20px;
}
function calculateRental() {
// 1. Get Input Values
var price = parseFloat(document.getElementById('rp_price').value);
var downPercent = parseFloat(document.getElementById('rp_down').value);
var rate = parseFloat(document.getElementById('rp_rate').value);
var term = parseFloat(document.getElementById('rp_term').value);
var closing = parseFloat(document.getElementById('rp_closing').value);
var rehab = parseFloat(document.getElementById('rp_rehab').value);
var rent = parseFloat(document.getElementById('rp_rent').value);
var vacancyRate = parseFloat(document.getElementById('rp_vacancy').value);
var tax = parseFloat(document.getElementById('rp_tax').value);
var insurance = parseFloat(document.getElementById('rp_insurance').value);
var hoa = parseFloat(document.getElementById('rp_hoa').value);
var maintenance = parseFloat(document.getElementById('rp_maintenance').value);
var mgmtPercent = parseFloat(document.getElementById('rp_mgmt').value);
// Validation
if (isNaN(price) || isNaN(downPercent) || isNaN(rate) || isNaN(term) || isNaN(rent)) {
alert("Please enter valid numbers for the primary fields.");
return;
}
// 2. Calculate Mortgage (Principal & Interest)
var downPaymentAmount = price * (downPercent / 100);
var loanAmount = price – downPaymentAmount;
var monthlyRate = (rate / 100) / 12;
var numPayments = term * 12;
var monthlyMortgage = 0;
if (rate > 0) {
monthlyMortgage = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numPayments)) / (Math.pow(1 + monthlyRate, numPayments) – 1);
} else {
monthlyMortgage = loanAmount / numPayments;
}
// 3. Calculate Monthly Operating Income
var vacancyAmount = rent * (vacancyRate / 100);
var effectiveGrossIncome = rent – vacancyAmount;
// 4. Calculate Monthly Expenses (Operating + Mortgage)
var monthlyTax = tax / 12;
var monthlyInsurance = insurance / 12;
var monthlyHOA = hoa / 12;
var monthlyMaintenance = maintenance / 12;
var monthlyMgmt = effectiveGrossIncome * (mgmtPercent / 100);
var totalOperatingExpenses = monthlyTax + monthlyInsurance + monthlyHOA + monthlyMaintenance + monthlyMgmt;
var totalExpenses = totalOperatingExpenses + monthlyMortgage;
// 5. Calculate Metrics
var monthlyCashFlow = effectiveGrossIncome – totalExpenses;
var annualCashFlow = monthlyCashFlow * 12;
var annualNOI = (effectiveGrossIncome – totalOperatingExpenses) * 12;
var monthlyNOI = annualNOI / 12;
var totalCashInvested = downPaymentAmount + closing + rehab;
var cocReturn = 0;
if (totalCashInvested > 0) {
cocReturn = (annualCashFlow / totalCashInvested) * 100;
}
var capRate = 0;
if (price > 0) {
capRate = (annualNOI / price) * 100;
}
// 6. Display Results
document.getElementById('res_monthly_cf').innerHTML = "$" + monthlyCashFlow.toFixed(2);
document.getElementById('res_coc').innerHTML = cocReturn.toFixed(2) + "%";
document.getElementById('res_cap').innerHTML = capRate.toFixed(2) + "%";
document.getElementById('res_noi').innerHTML = "$" + monthlyNOI.toFixed(2);
document.getElementById('res_cash_needed').innerHTML = "$" + totalCashInvested.toLocaleString();
document.getElementById('res_mortgage').innerHTML = "$" + monthlyMortgage.toFixed(2);
document.getElementById('res_expenses').innerHTML = "$" + totalExpenses.toFixed(2);
// Show container
document.getElementById('rp_result_container').style.display = "block";
}
Understanding Rental Property Cash Flow
Investing in real estate is one of the most reliable ways to build wealth, but the difference between a successful investment and a financial burden often comes down to one metric: Cash Flow. Our Rental Property Calculator is designed to help investors accurately project the financial performance of a potential acquisition by accounting for all income and expense variables.
What is Positive Cash Flow?
Positive cash flow occurs when a property's gross monthly income exceeds its total monthly expenses. This surplus income is profit that goes directly into your pocket. Expenses include not just the mortgage, but also taxes, insurance, vacancy provisions, maintenance reserves, and property management fees.
For example, if you collect $2,000 in rent and your total expenses (mortgage + operations) are $1,600, your Monthly Cash Flow is $400. Over a year, this accumulates to $4,800 in passive income.
Key Metrics Explained
Cash on Cash Return (CoC)
This is arguably the most important metric for leverage-based investors. It measures the annual return on the actual cash you invested, rather than the total purchase price.
Formula: Annual Cash Flow / Total Cash Invested
If you invest $50,000 (down payment + closing costs) to buy a property that generates $5,000 in annual positive cash flow, your Cash on Cash return is 10%. This allows you to compare real estate returns directly against other investment vehicles like stocks or bonds.
Cap Rate (Capitalization Rate)
The Cap Rate measures the natural rate of return of a property assuming it was bought entirely with cash (no loan). It is calculated by dividing the Net Operating Income (NOI) by the Purchase Price.
Cap Rate is useful for comparing the intrinsic value of different properties regardless of financing. A higher Cap Rate generally indicates a higher potential return, though often accompanied by higher risk (e.g., properties in less desirable neighborhoods).
Net Operating Income (NOI)
NOI is the total income the property generates minus all necessary operating expenses. Critical Note: NOI does not include mortgage payments. It represents the profitability of the property itself, excluding the financing structure.
How to Use This Calculator
To get the most accurate results, ensure you input realistic numbers for:
- Vacancy Rate: No property is occupied 100% of the time. A standard conservative estimate is 5% to 8% (roughly 2-4 weeks of vacancy per year).
- Maintenance: Even if a house is new, things break. budgeting 1% of the property value annually or 10-15% of the monthly rent is a prudent safety net.
- Property Management: If you plan to hire a professional manager, they typically charge between 8% and 12% of the collected monthly rent.
By inputting these detailed expenses, you avoid the "phantom cash flow" trap where investors underestimate costs and find themselves losing money despite high rental income.