Annual Percentage Rate Monthly Payment Calculator

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Mortgage Calculator

Understanding Your Mortgage Payment

A mortgage is a loan used to purchase real estate. The monthly mortgage payment is typically composed of principal and interest. Over time, as you make payments, you pay down the principal balance of the loan. The interest paid is the cost of borrowing the money.

The formula used to calculate your monthly mortgage payment (M) is:

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

Where:

  • P = Principal loan amount (the amount you borrow)
  • i = Monthly interest rate (annual interest rate divided by 12)
  • n = Total number of payments over the loan's lifetime (loan term in years multiplied by 12)

This calculator helps you estimate your P&I (Principal and Interest) payment, which is a significant component of your total monthly housing cost. Keep in mind that your actual monthly payment may also include property taxes, homeowner's insurance, and potentially private mortgage insurance (PMI) or homeowner's association (HOA) fees.

Example Calculation:

Let's say you're looking to buy a home and need a mortgage of $200,000 with an annual interest rate of 5% over a 30-year term.

  • Principal (P): $200,000
  • Annual Interest Rate: 5%
  • Monthly Interest Rate (i): 5% / 12 = 0.05 / 12 ≈ 0.0041667
  • Loan Term: 30 years
  • Total Number of Payments (n): 30 years * 12 months/year = 360

Using the formula, the estimated monthly Principal & Interest payment would be approximately $1,073.64.

function calculateMortgage() { var loanAmount = parseFloat(document.getElementById("loanAmount").value); var interestRate = parseFloat(document.getElementById("interestRate").value); var loanTerm = parseFloat(document.getElementById("loanTerm").value); var resultDiv = document.getElementById("result"); if (isNaN(loanAmount) || isNaN(interestRate) || isNaN(loanTerm) || loanAmount <= 0 || interestRate < 0 || loanTerm <= 0) { resultDiv.innerHTML = "Please enter valid numbers for all fields."; return; } var monthlyInterestRate = interestRate / 100 / 12; var numberOfPayments = loanTerm * 12; var monthlyPayment = loanAmount * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1); if (isNaN(monthlyPayment) || !isFinite(monthlyPayment)) { resultDiv.innerHTML = "Calculation error. Please check your inputs."; return; } resultDiv.innerHTML = "

Estimated Monthly Payment (P&I):

$" + monthlyPayment.toFixed(2) + ""; }

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