Free Mortgage Payoff Calculator

let steps = “”; const currencySymbol = “$”, fixedCurrency = “USD”; function calculateMortgagePayoff() { steps = “”; const loanAmount = parseFloat(document.getElementById(“loanAmount”).value); const interestRate = parseFloat(document.getElementById(“interestRate”).value) / 100 / 12; const loanTerm = parseFloat(document.getElementById(“loanTerm”).value) * 12; const extraPayment = parseFloat(document.getElementById(“extraPayment”).value); if (isNaN(loanAmount) || isNaN(interestRate) || isNaN(loanTerm) || isNaN(extraPayment) || loanAmount <= 0 || interestRate <= 0 || loanTerm <= 0) { alert("Please enter valid positive values for all fields."); return; } const monthlyPayment = (loanAmount * interestRate) / (1 – Math.pow(1 + interestRate, -loanTerm)); const totalMonthlyPayment = monthlyPayment + extraPayment; const payoffTime = Math.log(totalMonthlyPayment / (totalMonthlyPayment – loanAmount * interestRate)) / Math.log(1 + interestRate) / 12; document.getElementById("monthlyPayment").value = formatCurrency(monthlyPayment); document.getElementById("payoffTime").value = payoffTime.toFixed(2); steps += `Inputs:
Loan Amount: ${formatCurrency(loanAmount)}
Interest Rate: ${(interestRate * 100).toFixed(2)}%
Loan Term: ${(loanTerm / 12)} years
Extra Payment: ${formatCurrency(extraPayment)}

`; steps += `Formulas:
Monthly Payment = Loan Amount × Interest Rate / (1 – (1 + Interest Rate)^-Loan Term)
Payoff Time = log(Total Monthly Payment / (Total Monthly Payment – Loan Amount × Interest Rate)) / log(1 + Interest Rate)

`; steps += `Results:
Monthly Payment: ${formatCurrency(monthlyPayment)}
Payoff Time: ${payoffTime.toFixed(2)} years
`; if (document.getElementById(“calculationSteps”).style.display === “block”) { document.getElementById(“calculationSteps”).innerHTML = steps; } } function resetMortgagePayoff() { document.querySelectorAll(“#calculator input”).forEach(el => el.value = “”); steps = “”; document.getElementById(“calculationSteps”).innerHTML = “

Not calculated yet.

“; } function toggleCalculationSteps() { const s = document.getElementById(“calculationSteps”); const a = document.getElementById(“toggleArrow”); if (s.style.display === “none” || s.style.display === “”) { s.style.display = “block”; a.style.transform = “rotate(180deg)”; s.innerHTML = steps || “

Not calculated yet.

“; } else { s.style.display = “none”; a.style.transform = “rotate(0deg)”; } } function formatCurrency(n) { return currencySymbol + n.toFixed(2) + ” ” + fixedCurrency; }