This calculator helps you estimate how much car you can realistically afford based on your income, expenses, and desired loan terms. Understanding your car loan affordability is a crucial step before you start browsing dealerships.
function calculateAffordability() {
var monthlyIncome = parseFloat(document.getElementById("monthlyIncome").value);
var existingDebts = parseFloat(document.getElementById("existingDebts").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var loanTermYears = parseInt(document.getElementById("loanTermYears").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var maxPaymentPercentage = parseFloat(document.getElementById("maxPaymentPercentage").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// Input validation
if (isNaN(monthlyIncome) || monthlyIncome <= 0 ||
isNaN(existingDebts) || existingDebts < 0 ||
isNaN(downPayment) || downPayment < 0 ||
isNaN(loanTermYears) || loanTermYears <= 0 ||
isNaN(interestRate) || interestRate < 0 ||
isNaN(maxPaymentPercentage) || maxPaymentPercentage 100) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields. The percentage must be between 1 and 100.";
return;
}
// Calculate maximum affordable monthly payment
var maxAffordableMonthlyPayment = monthlyIncome * (maxPaymentPercentage / 100);
var remainingIncomeForCar = maxAffordableMonthlyPayment – existingDebts;
if (remainingIncomeForCar 0) {
// Formula for present value of an ordinary annuity
// PV = PMT * [1 – (1 + r)^-n] / r
maxLoanAmount = remainingIncomeForCar * (1 – Math.pow(1 + monthlyInterestRate, -loanTermMonths)) / monthlyInterestRate;
} else {
// If interest rate is 0, loan amount is simply payment * term
maxLoanAmount = remainingIncomeForCar * loanTermMonths;
}
var totalAffordableCarPrice = maxLoanAmount + downPayment;
// Display results
var formattedAffordableCarPrice = totalAffordableCarPrice.toLocaleString('en-US', { style: 'currency', currency: 'USD' });
var formattedMaxLoanAmount = maxLoanAmount.toLocaleString('en-US', { style: 'currency', currency: 'USD' });
var formattedMaxMonthlyPayment = maxAffordableMonthlyPayment.toLocaleString('en-US', { style: 'currency', currency: 'USD' });
resultDiv.innerHTML = "
Your Estimated Car Affordability:
" +
"Maximum Affordable Car Price: " + formattedAffordableCarPrice + "" +
"Maximum Loan Amount You Can Qualify For: " + formattedMaxLoanAmount + "" +
"Maximum Estimated Monthly Payment: " + remainingIncomeForCar.toLocaleString('en-US', { style: 'currency', currency: 'USD' }) + " (out of " + formattedMaxMonthlyPayment + " total budget)" +
"Note: This is an estimate. Actual loan offers may vary based on credit score, lender policies, and vehicle specifics.";
}