Home Affordability Calculator

How to Use This Home Affordability Calculator

Enter your annual gross income (before taxes), total monthly debt payments (car loans, student loans, credit cards), and your planned down payment. Adjust the interest rate slider to match current mortgage rates, set your loan term, and optionally add property tax rate, HOA fees, and home insurance costs. Hit "Calculate Affordability" to instantly see the maximum home price you can afford, your estimated monthly payment, and a full year-by-year amortization breakdown.

Why This Matters

Buying a home is likely the largest financial decision you'll ever make — and going in without knowing your budget is like grocery shopping without a wallet. Lenders use two key rules: the 28% front-end rule (your total housing payment shouldn't exceed 28% of gross monthly income) and the 36% back-end rule (all monthly debts including housing shouldn't exceed 36% of gross income). The more conservative figure wins.

For example, a household earning $90,000/year has a gross monthly income of $7,500. Their max housing payment is $2,100 (28%). If they also carry $600/month in car and student loans, the back-end cap is $2,700 total debt — leaving only $2,100 for housing anyway. With a 6.5% rate, 30-year term, and 10% down, this translates to roughly a $330,000 home price. That number shifts dramatically with a larger down payment or lower interest rate — which is exactly why running scenarios before you start house-hunting can save you from falling in love with a house that will break your budget.

How It's Calculated

The calculator uses standard mortgage affordability formulas:

• Max PITI payment: Min(Gross Monthly Income × 28%, Gross Monthly Income × 36% − Monthly Debts)
• Monthly PI budget: Max PITI − Monthly Taxes − Monthly Insurance − Monthly HOA
• Loan amount: P = PI × [(1−(1+r)^−n) / r] where r = monthly rate, n = total months
• Max home price: Loan Amount + Down Payment
• Total interest: (Monthly PI × n) − Loan Amount

Each year's amortization is calculated by summing 12 months of standard amortization: each month, interest = remaining balance × monthly rate; principal = monthly payment − interest.

Tips & Common Mistakes

• Don't forget closing costs. Budget 2–5% of the home price ($6,000–$15,000 on a $300K home) on top of your down payment — these must be paid at closing.
• Pre-approval ≠ affordability. Lenders may approve you for more than you're comfortable paying. Use this calculator to find your comfort zone, not just your maximum.
• Property taxes vary widely. New Jersey averages ~2.2%, while Hawaii is ~0.3%. Always use your target area's actual rate.
• PMI adds cost. If your down payment is less than 20%, expect to add Private Mortgage Insurance (~0.5–1.5% of the loan annually) to your monthly payment.
• Emergency fund matters. Don't drain your savings for a larger down payment. Experts recommend keeping 3–6 months of expenses liquid even after closing.

Frequently Asked Questions

What's the difference between front-end and back-end DTI?

Front-end DTI (debt-to-income) only counts your housing costs — principal, interest, taxes, and insurance — as a percentage of your gross monthly income. Back-end DTI includes all monthly debt obligations including housing, car loans, student loans, and credit cards. Most conventional lenders want front-end below 28% and back-end below 36–43%.

How much should I put down on a house?

The traditional target is 20%, which avoids PMI (Private Mortgage Insurance) and results in lower monthly payments. However, many loan programs allow 3–10% down, and FHA loans allow as little as 3.5%. A larger down payment lowers your loan amount and total interest paid, but make sure you keep enough cash reserves for closing costs and emergencies.

Does this calculator account for PMI?

This calculator doesn't automatically add PMI, but you should factor it in manually if your down payment is less than 20%. PMI typically costs 0.5–1.5% of the loan amount per year. Simply add that monthly cost to the "HOA fees" field as a workaround to see the true monthly payment impact.

What interest rate should I use?

Use current 30-year fixed mortgage rates from a site like Freddie Mac's weekly survey or your lender's website. Rates change daily and vary based on your credit score, loan type, and down payment amount. For planning purposes, it's wise to run scenarios at current rates plus 0.5–1% to stress-test your budget against potential rate increases.