Formula to Calculate Interest Rate on a Loan

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Rental Property Calculator

Purchase Information
Income & Expenses (Monthly)
Monthly Mortgage (P&I): $0.00
Total Monthly Expenses: $0.00
Net Operating Income (NOI): $0.00
Monthly Cash Flow: $0.00
Cash on Cash Return: 0.00%
Cap Rate: 0.00%

Understanding Rental Property Cash Flow Analysis

Investing in real estate is one of the most reliable ways to build wealth, but the difference between a profitable investment and a financial burden often lies in the numbers. This Rental Property Cash Flow Calculator is designed to help investors analyze the potential profitability of a residential real estate deal.

Key Metrics in Real Estate Investing

When evaluating a rental property, focusing solely on the rental income isn't enough. You must consider all operating expenses and debt service to understand the true return on investment (ROI).

1. Net Operating Income (NOI)

NOI is a fundamental calculation used to analyze the profitability of income-generating real estate investments. It equals all revenue from the property, minus all reasonably necessary operating expenses. Note that NOI represents the income before mortgage payments and taxes.

Formula: Gross Income – Operating Expenses = NOI

2. Cash Flow

Cash flow is the net amount of cash moving into or out of your business at the end of the month. In rental real estate, positive cash flow means the rent collected exceeds the mortgage, taxes, insurance, and maintenance costs. This is "passive income" in your pocket.

3. Cash on Cash Return (CoC)

This metric measures the annual return the investor made on the property in relation to the amount of mortgage paid during the same year. It is considered one of the most important ROI metrics because it tells you how hard your actual cash investment is working.

Example: If you invest $50,000 cash (down payment + closing) and the property generates $5,000 in net annual cash flow, your CoC return is 10%.

4. Cap Rate (Capitalization Rate)

The Cap Rate indicates the rate of return that is expected to be generated on a real estate investment property. It is calculated by dividing the Net Operating Income (NOI) by the property asset value (Purchase Price). It helps compare properties regardless of how they are financed.

Real Life Example: The $250,000 Investment

Let's calculate the numbers for a typical single-family rental scenario to see how small expenses impact profitability.

  • Purchase Price: $250,000
  • Down Payment: 20% ($50,000)
  • Interest Rate: 6.5% on a 30-year fixed loan
  • Projected Rent: $2,200/month

After factoring in property taxes ($250/mo), insurance ($100/mo), vacancy reserves (5%), and maintenance reserves (10%), your total operating expenses might hover around $580/month (excluding the mortgage). With a mortgage payment of roughly $1,264, your total cash outflow is $1,844.

Result: $2,200 Rent – $1,844 Total Outflow = $356 Monthly Cash Flow. This results in a Cash on Cash return of roughly 7.7% per year.

Why Vacancy and Maintenance Reserves Matter

Many novice investors make the mistake of assuming 100% occupancy and $0 in repairs. This calculator forces you to account for these realities. A Vacancy Rate of 5-8% is standard in most markets, accounting for turnover time between tenants. Similarly, setting aside 10-15% for Maintenance and CapEx (Capital Expenditures like a new roof or HVAC) ensures you aren't underwater when a big repair bill hits.

function calculateRental() { // 1. Retrieve Inputs var price = parseFloat(document.getElementById('rpcPrice').value) || 0; var downPercent = parseFloat(document.getElementById('rpcDownPercent').value) || 0; var closingCosts = parseFloat(document.getElementById('rpcClosingCosts').value) || 0; var rate = parseFloat(document.getElementById('rpcRate').value) || 0; var term = parseFloat(document.getElementById('rpcTerm').value) || 0; var rent = parseFloat(document.getElementById('rpcRent').value) || 0; var annualTax = parseFloat(document.getElementById('rpcTax').value) || 0; var annualIns = parseFloat(document.getElementById('rpcInsurance').value) || 0; var monthlyHOA = parseFloat(document.getElementById('rpcHOA').value) || 0; var vacancyRate = parseFloat(document.getElementById('rpcVacancy').value) || 0; var maintRate = parseFloat(document.getElementById('rpcMaintenance').value) || 0; // 2. Loan Calculations var downAmount = price * (downPercent / 100); var loanAmount = price – downAmount; var monthlyRate = (rate / 100) / 12; var totalPayments = term * 12; var monthlyMortgage = 0; if (loanAmount > 0 && rate > 0) { monthlyMortgage = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, totalPayments)) / (Math.pow(1 + monthlyRate, totalPayments) – 1); } else if (loanAmount > 0 && rate === 0) { monthlyMortgage = loanAmount / totalPayments; } // 3. Expense Calculations var vacancyCost = rent * (vacancyRate / 100); var maintCost = rent * (maintRate / 100); var monthlyTax = annualTax / 12; var monthlyIns = annualIns / 12; // Operating Expenses (OpEx) = Tax + Ins + HOA + Vacancy + Maintenance // NOTE: Mortgage is NOT an operating expense for NOI, but IS for Cash Flow. var totalOpEx = monthlyTax + monthlyIns + monthlyHOA + vacancyCost + maintCost; // 4. Income Metrics // Net Operating Income (NOI) = Gross Rent – OpEx var noiMonthly = rent – totalOpEx; var noiAnnual = noiMonthly * 12; // Cash Flow = NOI – Mortgage var cashFlowMonthly = noiMonthly – monthlyMortgage; var cashFlowAnnual = cashFlowMonthly * 12; // 5. ROI Metrics // Cap Rate = (Annual NOI / Purchase Price) * 100 var capRate = 0; if (price > 0) { capRate = (noiAnnual / price) * 100; } // Cash on Cash Return = (Annual Cash Flow / Total Cash Invested) * 100 // Total Cash Invested = Down Payment + Closing Costs var totalInvested = downAmount + closingCosts; var cashOnCash = 0; if (totalInvested > 0) { cashOnCash = (cashFlowAnnual / totalInvested) * 100; } // 6. Formatting Helper function formatMoney(num) { return '$' + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,'); } // 7. Update DOM document.getElementById('resMortgage').innerText = formatMoney(monthlyMortgage); // For display "Total Expenses" usually includes mortgage for the layperson's "Monthly Bill", // but in strict accounting OpEx excludes mortgage. // Let's display "Total Cash Outflow" (OpEx + Mortgage) for the user to understand total checks written. var totalOutflow = totalOpEx + monthlyMortgage; document.getElementById('resExpenses').innerText = formatMoney(totalOutflow); document.getElementById('resNOI').innerText = formatMoney(noiMonthly); var cfElement = document.getElementById('resCashFlow'); cfElement.innerText = formatMoney(cashFlowMonthly); if(cashFlowMonthly >= 0) { cfElement.className = "rpc-result-value rpc-positive"; } else { cfElement.className = "rpc-result-value rpc-negative"; } document.getElementById('resCoc').innerText = cashOnCash.toFixed(2) + '%'; document.getElementById('resCapRate').innerText = capRate.toFixed(2) + '%'; // Show results document.getElementById('rpcResults').style.display = 'block'; }

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