How to Calculate My Mortgage Interest Rate

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Rental Property Cash Flow Calculator

Acquisition & Loan

Income & Expenses

Monthly Mortgage P&I: $0.00
Total Monthly Expenses: $0.00
Net Operating Income (Monthly): $0.00
Monthly Cash Flow: $0.00
Cash on Cash Return (ROI): 0.00%

Understanding Rental Property Analysis

Investing in real estate is one of the most reliable ways to build wealth, but simply buying a property and renting it out doesn't guarantee a profit. To succeed, investors must perform a detailed Cash Flow Analysis. This calculator helps you determine if a potential rental property will put money in your pocket every month (positive cash flow) or take it out (negative cash flow).

How is Cash Flow Calculated?

Cash flow is the net amount of cash moving into or out of an investment. In real estate, the formula is:

  • Gross Income: Total rent collected plus any other income (laundry, parking, etc.).
  • Operating Expenses: Property taxes, insurance, maintenance reserves, management fees, and HOA dues.
  • Debt Service: The principal and interest payments on your mortgage.

Cash Flow = Gross Income – (Operating Expenses + Debt Service)

What is Cash-on-Cash Return?

While cash flow tells you dollar amounts, Cash-on-Cash Return (CoC) measures the efficiency of your investment. It calculates the annual return you are making on the actual cash you invested (Down Payment + Closing Costs + Rehab Costs).

For example, if you invest $50,000 cash to buy a property and it generates $5,000 in positive cash flow per year, your Cash-on-Cash return is 10%. Most investors aim for a CoC return of 8% to 12% or higher.

Why You Should Estimate Expenses Conservatively

A common mistake for new landlords is underestimating expenses. Always account for Vacancy (times when the unit is empty) and Maintenance (saving for future repairs like a new roof or water heater). This calculator allows you to set a percentage reserve for these costs to give you a realistic picture of the property's profitability.

function calculateRentalROI() { // 1. Get Input Values var price = parseFloat(document.getElementById('rpPurchasePrice').value); var downPayPercent = parseFloat(document.getElementById('rpDownPayment').value); var interestRate = parseFloat(document.getElementById('rpInterestRate').value); var loanTerm = parseFloat(document.getElementById('rpLoanTerm').value); var closingCosts = parseFloat(document.getElementById('rpClosingCosts').value); var monthlyRent = parseFloat(document.getElementById('rpMonthlyRent').value); var annualTax = parseFloat(document.getElementById('rpPropTax').value); var annualIns = parseFloat(document.getElementById('rpInsurance').value); var monthlyHOA = parseFloat(document.getElementById('rpHOA').value); var maintPercent = parseFloat(document.getElementById('rpMaintenance').value); // 2. Validate Inputs if (isNaN(price) || isNaN(monthlyRent) || isNaN(interestRate) || isNaN(loanTerm)) { alert("Please fill in all required fields (Price, Rent, Interest Rate, Loan Term) with valid numbers."); return; } // Handle optional empty fields as 0 if (isNaN(downPayPercent)) downPayPercent = 0; if (isNaN(closingCosts)) closingCosts = 0; if (isNaN(annualTax)) annualTax = 0; if (isNaN(annualIns)) annualIns = 0; if (isNaN(monthlyHOA)) monthlyHOA = 0; if (isNaN(maintPercent)) maintPercent = 0; // 3. Perform Calculations // Loan Calculations var downPayment = price * (downPayPercent / 100); var loanAmount = price – downPayment; var monthlyRate = (interestRate / 100) / 12; var totalPayments = loanTerm * 12; // Mortgage Payment (Principal + Interest) var monthlyMortgage = 0; if (loanAmount > 0 && interestRate > 0) { monthlyMortgage = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, totalPayments)) / (Math.pow(1 + monthlyRate, totalPayments) – 1); } else if (loanAmount > 0 && interestRate === 0) { monthlyMortgage = loanAmount / totalPayments; } // Expense Calculations var monthlyTax = annualTax / 12; var monthlyIns = annualIns / 12; var monthlyMaint = monthlyRent * (maintPercent / 100); var totalMonthlyExpenses = monthlyMortgage + monthlyTax + monthlyIns + monthlyHOA + monthlyMaint; // Profit Calculations var monthlyCashFlow = monthlyRent – totalMonthlyExpenses; var annualCashFlow = monthlyCashFlow * 12; var totalInitialCashInvested = downPayment + closingCosts; var cashOnCashROI = 0; if (totalInitialCashInvested > 0) { cashOnCashROI = (annualCashFlow / totalInitialCashInvested) * 100; } // NOI (Net Operating Income) = Income – Operating Expenses (Excluding Mortgage) var operatingExpenses = monthlyTax + monthlyIns + monthlyHOA + monthlyMaint; var monthlyNOI = monthlyRent – operatingExpenses; // 4. Update UI document.getElementById('resMortgage').innerText = formatCurrency(monthlyMortgage); document.getElementById('resExpenses').innerText = formatCurrency(totalMonthlyExpenses); document.getElementById('resNOI').innerText = formatCurrency(monthlyNOI); var cashFlowElem = document.getElementById('resCashFlow'); cashFlowElem.innerText = formatCurrency(monthlyCashFlow); if(monthlyCashFlow >= 0) { cashFlowElem.style.color = "#27ae60"; } else { cashFlowElem.style.color = "#c0392b"; } var cocElem = document.getElementById('resCoC'); cocElem.innerText = cashOnCashROI.toFixed(2) + "%"; if(cashOnCashROI >= 0) { cocElem.style.color = "#27ae60"; } else { cocElem.style.color = "#c0392b"; } // Show results section document.getElementById('rpResults').style.display = "block"; } function formatCurrency(num) { return "$" + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,'); }

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