Cash flow is the lifeblood of any rental property investment. It represents the net amount of money moving into or out of your business every month. Positive cash flow means your property is generating profit after all expenses are paid, while negative cash flow implies you are losing money to hold the asset.
Using a Rental Property Cash Flow Calculator helps investors analyze deals objectively before signing a contract. It accounts for not just the mortgage, but the "silent killers" of profitability like vacancy rates, repairs, and capital expenditures (CapEx).
Key Metrics Explained
1. Net Operating Income (NOI)
NOI is a calculation used to analyze the profitability of income-generating real estate investments. It equals all revenue from the property, minus all necessary operating expenses. Note that NOI excludes mortgage payments (principal and interest) and income taxes.
Formula: NOI = Gross Operating Income – Operating Expenses
2. Cash-on-Cash Return (CoC)
This is arguably the most important metric for rental investors. It measures the annual return you made on the actual cash you invested (down payment, closing costs, and rehab costs), rather than the total price of the property.
Many new investors fail because they only calculate the mortgage, tax, and insurance. To get an accurate picture, you must estimate:
Vacancy Rate: Properties won't be rented 365 days a year. A standard safe estimate is 5-8%.
Repairs & Maintenance: For routine fixes (leaky faucets, painting). Budget 5-10% of rent.
CapEx: Saving for big-ticket items like a new roof or HVAC system. Budget 5-10% of rent.
Property Management: If you hire a pro, they typically charge 8-12% of the monthly rent.
What is a "Good" Cash Flow?
While this varies by market and strategy, many investors aim for at least $100 – $200 per door, per month in pure cash flow. For Cash-on-Cash return, a return of 8% to 12% is generally considered strong in the stock market, so real estate investors often look for returns exceeding that to justify the illiquidity of the asset.
function calculateRental() {
// Get Input Values
var rent = parseFloat(document.getElementById('monthlyRent').value) || 0;
var otherInc = parseFloat(document.getElementById('otherIncome').value) || 0;
var mortgage = parseFloat(document.getElementById('mortgage').value) || 0;
var taxes = parseFloat(document.getElementById('propertyTax').value) || 0;
var insurance = parseFloat(document.getElementById('insurance').value) || 0;
var hoa = parseFloat(document.getElementById('hoa').value) || 0;
var vacancyPct = parseFloat(document.getElementById('vacancyRate').value) || 0;
var repairsPct = parseFloat(document.getElementById('repairs').value) || 0;
var capexPct = parseFloat(document.getElementById('capex').value) || 0;
var mgmtPct = parseFloat(document.getElementById('management').value) || 0;
var cashInvested = parseFloat(document.getElementById('downPayment').value) || 0;
// Calculations
var grossIncome = rent + otherInc;
// Calculate Variable Costs based on Rent
var vacancyCost = rent * (vacancyPct / 100);
var repairsCost = rent * (repairsPct / 100);
var capexCost = rent * (capexPct / 100);
var mgmtCost = rent * (mgmtPct / 100);
var totalVariable = vacancyCost + repairsCost + capexCost + mgmtCost;
var totalFixed = mortgage + taxes + insurance + hoa;
var totalExpenses = totalFixed + totalVariable;
var monthlyCashFlow = grossIncome – totalExpenses;
var annualCashFlow = monthlyCashFlow * 12;
// NOI Calculation (Gross Income – Operating Expenses EXCLUDING Mortgage)
// Operating Expenses = Taxes + Ins + HOA + Variable Costs
var operatingExpenses = taxes + insurance + hoa + totalVariable;
var noi = (grossIncome – operatingExpenses) * 12;
// CoC Return
var coc = 0;
if (cashInvested > 0) {
coc = (annualCashFlow / cashInvested) * 100;
}
// Formatting currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
});
// Display Results
document.getElementById('results').style.display = 'block';
document.getElementById('resGrossIncome').innerText = formatter.format(grossIncome);
document.getElementById('resTotalExpenses').innerText = formatter.format(totalExpenses);
var cashFlowEl = document.getElementById('resCashFlow');
cashFlowEl.innerText = formatter.format(monthlyCashFlow);
if(monthlyCashFlow >= 0) {
cashFlowEl.className = "positive-cf";
} else {
cashFlowEl.className = "negative-cf";
}
document.getElementById('resNOI').innerText = formatter.format(noi);
var annualFlowEl = document.getElementById('resAnnualFlow');
annualFlowEl.innerText = formatter.format(annualCashFlow);
if(annualCashFlow >= 0) {
annualFlowEl.className = "positive-cf";
} else {
annualFlowEl.className = "negative-cf";
}
var cocEl = document.getElementById('resCoC');
cocEl.innerText = coc.toFixed(2) + "%";
if(coc >= 0) {
cocEl.className = "positive-cf";
} else {
cocEl.className = "negative-cf";
}
}