.rp-calc-wrapper {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 20px auto;
border: 1px solid #e0e0e0;
border-radius: 8px;
background: #fff;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.rp-calc-header {
background: #2c3e50;
color: #fff;
padding: 20px;
border-radius: 8px 8px 0 0;
text-align: center;
}
.rp-calc-header h2 {
margin: 0;
font-size: 24px;
}
.rp-calc-body {
padding: 25px;
display: flex;
flex-wrap: wrap;
gap: 20px;
}
.rp-input-group {
flex: 1 1 300px;
}
.rp-input-row {
margin-bottom: 15px;
}
.rp-input-row label {
display: block;
margin-bottom: 5px;
font-weight: 600;
color: #333;
font-size: 14px;
}
.rp-input-row input {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.rp-input-row input:focus {
border-color: #3498db;
outline: none;
}
.rp-btn-container {
width: 100%;
text-align: center;
margin-top: 10px;
}
.rp-calc-btn {
background: #27ae60;
color: white;
border: none;
padding: 12px 30px;
font-size: 18px;
border-radius: 5px;
cursor: pointer;
transition: background 0.3s;
font-weight: bold;
}
.rp-calc-btn:hover {
background: #219150;
}
.rp-results {
background: #f8f9fa;
padding: 20px;
border-top: 1px solid #e0e0e0;
border-radius: 0 0 8px 8px;
display: none;
}
.rp-result-grid {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
gap: 15px;
}
.rp-result-item {
background: #fff;
padding: 15px;
border-radius: 6px;
border: 1px solid #ddd;
text-align: center;
}
.rp-result-label {
font-size: 13px;
color: #7f8c8d;
text-transform: uppercase;
letter-spacing: 0.5px;
margin-bottom: 5px;
}
.rp-result-value {
font-size: 24px;
font-weight: 700;
color: #2c3e50;
}
.rp-result-value.positive {
color: #27ae60;
}
.rp-result-value.negative {
color: #c0392b;
}
.rp-article {
max-width: 800px;
margin: 40px auto;
line-height: 1.6;
color: #333;
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}
.rp-article h2 {
color: #2c3e50;
border-bottom: 2px solid #3498db;
padding-bottom: 10px;
margin-top: 30px;
}
.rp-article h3 {
color: #34495e;
margin-top: 25px;
}
.rp-article p {
margin-bottom: 15px;
}
.rp-article ul {
margin-bottom: 15px;
padding-left: 20px;
}
.rp-article li {
margin-bottom: 8px;
}
function calculateRentalCashFlow() {
// 1. Get Input Values
var price = parseFloat(document.getElementById('rpPrice').value);
var downPaymentPercent = parseFloat(document.getElementById('rpDownPayment').value);
var interestRate = parseFloat(document.getElementById('rpInterest').value);
var loanTermYears = parseFloat(document.getElementById('rpTerm').value);
var monthlyRent = parseFloat(document.getElementById('rpRent').value);
var annualTaxes = parseFloat(document.getElementById('rpTaxes').value);
var annualInsurance = parseFloat(document.getElementById('rpInsurance').value);
var monthlyMaintenance = parseFloat(document.getElementById('rpMaintenance').value);
var vacancyRate = parseFloat(document.getElementById('rpVacancy').value);
// 2. Validate Inputs
if (isNaN(price) || isNaN(downPaymentPercent) || isNaN(interestRate) || isNaN(loanTermYears) || isNaN(monthlyRent)) {
alert("Please enter valid numbers for all fields.");
return;
}
// 3. Calculate Mortgage Logic
var downPaymentAmount = price * (downPaymentPercent / 100);
var loanAmount = price – downPaymentAmount;
var monthlyRate = (interestRate / 100) / 12;
var totalPayments = loanTermYears * 12;
var monthlyMortgage = 0;
if (interestRate > 0) {
monthlyMortgage = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, totalPayments)) / (Math.pow(1 + monthlyRate, totalPayments) – 1);
} else {
monthlyMortgage = loanAmount / totalPayments;
}
// 4. Calculate Expenses Logic
var monthlyTaxes = annualTaxes / 12;
var monthlyInsurance = annualInsurance / 12;
var monthlyVacancyCost = monthlyRent * (vacancyRate / 100);
var totalMonthlyOperatingExpenses = monthlyTaxes + monthlyInsurance + monthlyMaintenance + monthlyVacancyCost;
var totalMonthlyOutflow = monthlyMortgage + totalMonthlyOperatingExpenses;
// 5. Calculate Metrics
var monthlyCashFlow = monthlyRent – totalMonthlyOutflow;
var annualCashFlow = monthlyCashFlow * 12;
// Net Operating Income (NOI) = Income – Operating Expenses (Excluding Mortgage)
var annualNOI = (monthlyRent * 12) – (totalMonthlyOperatingExpenses * 12);
// Cap Rate = NOI / Price
var capRate = (annualNOI / price) * 100;
// Cash on Cash Return = Annual Cash Flow / Total Cash Invested
// Assuming Closing Costs are roughly 3% of price (simplified estimation for this calc)
var closingCosts = price * 0.03;
var totalCashInvested = downPaymentAmount + closingCosts;
var cashOnCash = (annualCashFlow / totalCashInvested) * 100;
// 6. Update UI
document.getElementById('rpResults').style.display = 'block';
// Helper for formatting currency
var fmt = new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' });
// Update elements
document.getElementById('resMortgage').innerText = fmt.format(monthlyMortgage);
document.getElementById('resExpenses').innerText = fmt.format(totalMonthlyOperatingExpenses);
document.getElementById('resCashInvested').innerText = fmt.format(totalCashInvested);
var cfEl = document.getElementById('resCashFlow');
cfEl.innerText = fmt.format(monthlyCashFlow);
cfEl.className = 'rp-result-value ' + (monthlyCashFlow >= 0 ? 'positive' : 'negative');
var cocEl = document.getElementById('resCoc');
cocEl.innerText = cashOnCash.toFixed(2) + "%";
cocEl.className = 'rp-result-value ' + (cashOnCash >= 0 ? 'positive' : 'negative');
document.getElementById('resCapRate').innerText = capRate.toFixed(2) + "%";
}
Understanding Rental Property Cash Flow
Successful real estate investing relies heavily on the math. Buying a property because it "looks nice" is a recipe for disaster. This Rental Property Cash Flow Calculator helps you evaluate the financial viability of a potential investment by analyzing income, expenses, and financing costs.
What is Positive Cash Flow?
Positive cash flow occurs when a property's gross monthly income (rent) exceeds the total of all monthly expenses, including the mortgage payment, taxes, insurance, and maintenance. This surplus cash is your profit.
Formula: Cash Flow = Total Income – (Operating Expenses + Debt Service)
Key Metrics Explained
- NOI (Net Operating Income): This measures the profitability of the property before adding in the mortgage payment. It is crucial for determining the raw potential of the asset.
- Cap Rate (Capitalization Rate): Calculated as NOI / Purchase Price. It represents the rate of return you would expect to generate on a real estate investment property if you paid all cash. A higher cap rate generally implies a better return but may come with higher risk.
- Cash on Cash Return (CoC): This is arguably the most important metric for investors using leverage (loans). It calculates the cash income earned on the cash invested.
Formula: Annual Cash Flow / Total Cash Invested (Down Payment + Closing Costs).
The 1% Rule
A common "rule of thumb" in real estate is the 1% rule, which states that the monthly rent should be at least 1% of the purchase price. While this rule is harder to meet in expensive markets, it serves as a quick filter to identify properties that are likely to cash flow positively.
Estimating Expenses Correctly
New investors often overestimate cash flow by underestimating expenses. Be sure to account for:
- Vacancy: Properties won't be occupied 365 days a year. A 5-8% vacancy allowance is standard.
- Maintenance (CapEx): Roofs, water heaters, and HVAC systems eventually break. Setting aside 10-15% of rent for repairs is prudent.
- Property Management: Even if you self-manage, you should factor in a 10% management fee to ensure the deal works if you decide to hire a manager later.
Use the calculator above to adjust these variables and stress-test your investment before making an offer.