The Real Interest Rate is Calculated as

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Mortgage Payment Calculator

Estimate your monthly house payments, including interest, taxes, and insurance.

30 Years 20 Years 15 Years 10 Years
Estimated Monthly Payment $0.00
Principal & Interest $0.00
Property Taxes $0.00
Homeowners Insurance $0.00
HOA Fees $0.00
Loan Amount $0.00
Total Interest Paid $0.00

How to Calculate Your Mortgage Payment

Understanding what goes into your monthly mortgage payment is crucial for budgeting a new home purchase. While the sticker price of a home gives you a starting point, your actual monthly obligation (often referred to as PITI) includes several other factors.

1. Principal & Interest (P&I)

This is the core of your mortgage payment. Principal is the money that goes toward paying down the loan balance, while Interest is the cost of borrowing that money from the lender. In the early years of a 30-year mortgage, the majority of this portion goes toward interest.

2. Property Taxes and Insurance

Most lenders require you to pay 1/12th of your annual property taxes and homeowners insurance premiums each month into an escrow account. Our calculator adds these annual costs (divided by 12) to give you a realistic "out-the-door" monthly cost.

Pro Tip: Don't forget Homeowners Association (HOA) fees. While these are rarely paid through your lender, they are a mandatory monthly cost for condos and many planned communities.

How Interest Rates Affect Affordability

Even a small difference in interest rates can have a massive impact on your monthly payment and total loan cost. For example, on a $300,000 loan, the difference between a 6% and a 7% interest rate is roughly $196 per month, which adds up to over $70,000 in extra interest over 30 years.

The Amortization Formula

This calculator uses the standard amortization formula to determine your Principal and Interest payment:

M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]

  • M = Total monthly payment
  • P = Principal loan amount
  • i = Monthly interest rate (Annual Rate / 12)
  • n = Number of months (Loan Term Years × 12)

Frequently Asked Questions

Does this calculator include PMI?
This specific tool calculates the standard PITI + HOA. If your down payment is less than 20%, you may also owe Private Mortgage Insurance (PMI), which typically costs between 0.5% and 1% of the loan amount annually.

How much house can I afford?
A general rule of thumb is the 28/36 rule: spend no more than 28% of your gross monthly income on housing costs and no more than 36% on total debt.

function calculateMortgage() { // 1. Get Input Values var homePrice = parseFloat(document.getElementById('homePrice').value); var downPayment = parseFloat(document.getElementById('downPayment').value); var termYears = parseFloat(document.getElementById('loanTerm').value); var annualRate = parseFloat(document.getElementById('interestRate').value); var annualTax = parseFloat(document.getElementById('propertyTax').value); var annualInsurance = parseFloat(document.getElementById('homeInsurance').value); var monthlyHOA = parseFloat(document.getElementById('hoaFees').value); // 2. Validate Inputs if (isNaN(homePrice) || homePrice <= 0) { alert("Please enter a valid Home Price."); return; } if (isNaN(downPayment) || downPayment < 0) { downPayment = 0; } if (isNaN(annualRate) || annualRate < 0) { annualRate = 0; } if (isNaN(annualTax)) annualTax = 0; if (isNaN(annualInsurance)) annualInsurance = 0; if (isNaN(monthlyHOA)) monthlyHOA = 0; // 3. Calculate Loan Variables var principal = homePrice – downPayment; if (principal < 0) { alert("Down payment cannot be greater than home price."); return; } // 4. Calculate P&I var monthlyRate = (annualRate / 100) / 12; var numberOfPayments = termYears * 12; var monthlyPrincipalInterest = 0; // Handle zero interest rate edge case if (annualRate === 0) { monthlyPrincipalInterest = principal / numberOfPayments; } else { // Standard Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ] var mathPower = Math.pow(1 + monthlyRate, numberOfPayments); monthlyPrincipalInterest = principal * ((monthlyRate * mathPower) / (mathPower – 1)); } // 5. Calculate Monthly Escrow Items var monthlyTaxPayment = annualTax / 12; var monthlyInsurancePayment = annualInsurance / 12; // 6. Calculate Totals var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTaxPayment + monthlyInsurancePayment + monthlyHOA; var totalCostOfLoan = (monthlyPrincipalInterest * numberOfPayments); var totalInterest = totalCostOfLoan – principal; // 7. Format Output (Currency) var formatter = new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD', minimumFractionDigits: 2 }); // 8. Update DOM Elements document.getElementById('principalInterest').innerHTML = formatter.format(monthlyPrincipalInterest); document.getElementById('monthlyTax').innerHTML = formatter.format(monthlyTaxPayment); document.getElementById('monthlyInsurance').innerHTML = formatter.format(monthlyInsurancePayment); document.getElementById('monthlyHOA').innerHTML = formatter.format(monthlyHOA); document.getElementById('totalMonthlyPayment').innerHTML = formatter.format(totalMonthlyPayment); // Additional Statistics document.getElementById('displayLoanAmount').innerHTML = formatter.format(principal); document.getElementById('totalInterestPaid').innerHTML = formatter.format(totalInterest); } // Initial calculation on load so the calculator doesn't look empty window.onload = function() { calculateMortgage(); };

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