Income and Mortgage Affordability Calculator
:root {
–primary-blue: #004a99;
–success-green: #28a745;
–light-background: #f8f9fa;
–border-color: #dee2e6;
–text-color: #333;
}
body {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
line-height: 1.6;
color: var(–text-color);
background-color: var(–light-background);
margin: 0;
padding: 20px;
display: flex;
justify-content: center;
align-items: flex-start;
min-height: 100vh;
}
.loan-calc-container {
background-color: #fff;
padding: 30px;
border-radius: 8px;
box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
max-width: 700px;
width: 100%;
border: 1px solid var(–border-color);
}
h1, h2 {
color: var(–primary-blue);
text-align: center;
margin-bottom: 20px;
}
.input-group {
margin-bottom: 20px;
display: flex;
flex-direction: column;
}
.input-group label {
display: block;
margin-bottom: 8px;
font-weight: bold;
color: var(–primary-blue);
}
.input-group input[type="number"],
.input-group input[type="text"] {
padding: 10px 12px;
border: 1px solid var(–border-color);
border-radius: 4px;
font-size: 1rem;
width: calc(100% – 24px); /* Adjust for padding */
}
.input-group input[type="number"]:focus,
.input-group input[type="text"]:focus {
outline: none;
border-color: var(–primary-blue);
box-shadow: 0 0 0 2px rgba(0, 74, 153, 0.2);
}
.button-group {
text-align: center;
margin-top: 25px;
}
button {
background-color: var(–primary-blue);
color: white;
padding: 12px 25px;
border: none;
border-radius: 5px;
font-size: 1.1rem;
cursor: pointer;
transition: background-color 0.3s ease, transform 0.2s ease;
font-weight: bold;
}
button:hover {
background-color: #003366;
transform: translateY(-2px);
}
button:active {
transform: translateY(0);
}
#result {
margin-top: 30px;
padding: 20px;
background-color: var(–success-green);
color: white;
border-radius: 6px;
text-align: center;
font-size: 1.4rem;
font-weight: bold;
border: 1px solid #1e8e3e;
box-shadow: 0 2px 10px rgba(40, 167, 69, 0.3);
}
#result span {
font-size: 1.1rem;
font-weight: normal;
display: block;
margin-top: 5px;
}
.article-section {
margin-top: 40px;
padding: 30px;
background-color: #fff;
border-radius: 8px;
border: 1px solid var(–border-color);
box-shadow: 0 4px 15px rgba(0, 0, 0, 0.05);
}
.article-section h2 {
color: var(–primary-blue);
text-align: left;
margin-bottom: 15px;
}
.article-section p, .article-section ul {
margin-bottom: 15px;
}
.article-section ul {
list-style-type: disc;
margin-left: 20px;
}
.article-section strong {
color: var(–primary-blue);
}
/* Responsive adjustments */
@media (max-width: 600px) {
.loan-calc-container {
padding: 20px;
}
button {
width: 100%;
padding: 15px;
font-size: 1rem;
}
#result {
font-size: 1.2rem;
}
#result span {
font-size: 0.9rem;
}
}
Income and Mortgage Affordability Calculator
Annual Household Income ($)
Total Monthly Debt Payments (Excluding Mortgage) ($)
Down Payment ($)
Estimated Mortgage Interest Rate (%)
Mortgage Loan Term (Years)
Annual Property Tax Rate (%)
Annual Homeowner's Insurance ($)
Annual Private Mortgage Insurance (PMI) if applicable ($)
= 20%)">
Calculate Affordability
Understanding Your Mortgage Affordability
Determining how much house you can afford is a crucial step in the home-buying process. This calculator helps estimate your potential mortgage affordability by considering your income, existing debts, and estimated housing costs. It's important to note that this is an estimation tool, and a lender will conduct a full financial assessment.
How the Calculator Works: Key Factors
Lenders use various metrics to assess your ability to repay a mortgage. Two common guidelines are the front-end ratio (housing ratio) and the back-end ratio (debt-to-income ratio or DTI) .
Front-End Ratio (Housing Ratio): This measures the percentage of your gross monthly income that goes towards housing expenses. Lenders often prefer this to be below 28%. Housing expenses typically include:
Principal & Interest (P&I) on the mortgage
Property Taxes (Taxes)
Homeowner's Insurance (Insurance)
Private Mortgage Insurance (PMI) if applicable
Back-End Ratio (Debt-to-Income Ratio – DTI): This measures the percentage of your gross monthly income that goes towards all monthly debt payments, including housing expenses. Lenders typically prefer this to be below 36% to 43%, though it can vary. This calculator includes your existing monthly debt payments (like car loans, student loans, credit cards) and the estimated housing expenses.
The Math Behind the Calculation
The calculator first estimates your maximum affordable monthly Principal & Interest (P&I) payment based on the DTI ratio. A common guideline is that your total monthly debt (including the estimated mortgage P&I) should not exceed 36% of your gross monthly income.
1. Calculate Gross Monthly Income: Gross Monthly Income = Annual Household Income / 12
2. Calculate Maximum Total Monthly Debt Allowed (based on 36% DTI): Max Total Monthly Debt = Gross Monthly Income * 0.36
3. Calculate Maximum Affordable Mortgage P&I Payment: Max P&I Payment = Max Total Monthly Debt - Total Monthly Debt Payments (Excluding Mortgage)
If Max P&I Payment is negative, it indicates that your existing debts already exceed the typical DTI threshold, making mortgage affordability unlikely under these assumptions.
4. Calculate Maximum Loan Amount: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
Where:
M = Maximum P&I Payment calculated aboveP = Principal loan amount (what we want to find)i = Monthly interest rate (Annual Interest Rate / 12 / 100)n = Total number of payments (Loan Term in Years * 12)
Rearranging to solve for P:
P = M * [ (1 + i)^n – 1] / [ i(1 + i)^n ]
5. Calculate Maximum Affordable Home Price: Max Home Price = Maximum Loan Amount + Down Payment
Important Considerations:
Lender Variations: Lenders have different DTI limits and underwriting standards.Credit Score: Your credit score significantly impacts interest rates and loan approval.Loan Programs: Different loan types (FHA, VA, Conventional) have varying requirements.Closing Costs: This calculator does not include closing costs, which are additional expenses.Affordability vs. Qualification: This tool estimates affordability; actual qualification depends on lender approval.Property Taxes & Insurance: These estimates can vary significantly based on location and property type.
Use this calculator as a starting point for your home-buying journey. Consult with a mortgage professional for personalized advice.
function calculateMortgageAffordability() {
var annualIncome = parseFloat(document.getElementById("annualIncome").value);
var monthlyDebt = parseFloat(document.getElementById("monthlyDebt").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseInt(document.getElementById("loanTerm").value);
var propertyTaxRate = parseFloat(document.getElementById("propertyTaxRate").value);
var homeInsurance = parseFloat(document.getElementById("homeInsurance").value);
var pmi = parseFloat(document.getElementById("pmi").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = "; // Clear previous results
// — Input Validation —
if (isNaN(annualIncome) || annualIncome <= 0 ||
isNaN(monthlyDebt) || monthlyDebt < 0 ||
isNaN(downPayment) || downPayment < 0 ||
isNaN(interestRate) || interestRate <= 0 ||
isNaN(loanTerm) || loanTerm <= 0 ||
isNaN(propertyTaxRate) || propertyTaxRate < 0 ||
isNaN(homeInsurance) || homeInsurance < 0 ||
isNaN(pmi) || pmi < 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// — Calculations —
// 1. Calculate Gross Monthly Income
var grossMonthlyIncome = annualIncome / 12;
// 2. Calculate Maximum Total Monthly Debt Allowed (using 36% DTI)
var maxTotalMonthlyDebt = grossMonthlyIncome * 0.36;
// 3. Calculate Maximum Affordable Mortgage P&I Payment
var maxMonthlyPI = maxTotalMonthlyDebt – monthlyDebt;
if (maxMonthlyPI <= 0) {
resultDiv.innerHTML = "Based on your income and existing debts, mortgage affordability is unlikely with these assumptions. Your current debts may exceed the typical DTI limits.";
return;
}
// Calculate monthly property tax, insurance, and PMI
var monthlyPropertyTax = (annualIncome * (propertyTaxRate / 100)) / 12; // Using annual income as a proxy for property value for tax rate
var monthlyHomeInsurance = homeInsurance / 12;
var monthlyPMI = pmi / 12;
// Calculate the maximum P&I payment affordable considering housing expenses
var maxAffordablePI = maxMonthlyPI – monthlyPropertyTax – monthlyHomeInsurance – monthlyPMI;
if (maxAffordablePI 0) {
var numerator = Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1;
var denominator = monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments);
maxLoanAmount = maxAffordablePI * (numerator / denominator);
} else { // Handle case of 0% interest rate, though unlikely for mortgages
maxLoanAmount = maxAffordablePI * numberOfPayments;
}
// Ensure loan amount is not negative
maxLoanAmount = Math.max(0, maxLoanAmount);
// 5. Calculate Maximum Affordable Home Price
var maxHomePrice = maxLoanAmount + downPayment;
// — Display Results —
var formattedMaxHomePrice = maxHomePrice.toLocaleString(undefined, { style: 'currency', currency: 'USD', minimumFractionDigits: 0, maximumFractionDigits: 0 });
var formattedMaxLoanAmount = maxLoanAmount.toLocaleString(undefined, { style: 'currency', currency: 'USD', minimumFractionDigits: 0, maximumFractionDigits: 0 });
var formattedMaxMonthlyPI = maxAffordablePI.toLocaleString(undefined, { style: 'currency', currency: 'USD', minimumFractionDigits: 2, maximumFractionDigits: 2 });
var formattedGrossMonthlyIncome = grossMonthlyIncome.toLocaleString(undefined, { style: 'currency', currency: 'USD', minimumFractionDigits: 2, maximumFractionDigits: 2 });
var formattedMaxTotalMonthlyDebt = maxTotalMonthlyDebt.toLocaleString(undefined, { style: 'currency', currency: 'USD', minimumFractionDigits: 2, maximumFractionDigits: 2 });
resultDiv.innerHTML = `
Estimated Max Home Price: ${formattedMaxHomePrice}
Based on a maximum DTI of 36%
Estimated Max Loan Amount: ${formattedMaxLoanAmount}
Estimated Max Affordable P&I Payment: ${formattedMaxMonthlyPI}
Your Estimated Gross Monthly Income: ${formattedGrossMonthlyIncome}
Your Estimated Max Total Monthly Debt (incl. mortgage): ${formattedMaxTotalMonthlyDebt}
`;
}