Calculate how much house you can afford based on income, debts, down payment, and current mortgage rates. Free home affordability calculator with DTI analysis.
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Home Affordability Calculatorとは？
A home affordability calculator helps you determine the maximum home price you can comfortably afford based on your financial situation. By analyzing your annual income, monthly debt obligations, down payment, and current mortgage rates, this tool applies the standard 28/36 debt-to-income (DTI) rules used by most lenders to calculate your realistic home buying budget.
The 28/36 rule states that your housing costs should not exceed 28% of gross monthly income (front-end ratio) and total debt payments should not exceed 36% (back-end ratio). This calculator uses the more restrictive of the two limits to give you a conservative, realistic estimate.
Beyond the maximum home price, the calculator provides a detailed monthly payment breakdown including principal and interest, property taxes, homeowners insurance, and PMI (if your down payment is less than 20%). It also shows affordability ranges — conservative, moderate, and aggressive — so you can choose the comfort level that fits your financial goals.
手順:
Enter your annual gross income before taxes.
Enter your total monthly debt payments (credit cards, car loans, student loans).
Enter your planned down payment amount.
Enter the current mortgage interest rate and desired loan term.
Enter your local property tax rate, annual home insurance cost, and estimated PMI.
Review your maximum home price, monthly payment breakdown, and DTI ratios.
Use the mode tabs to see a quick estimate or detailed breakdown with charts.
計算式
Monthly Income = Annual Income / 12
Max Housing Payment (28% rule) = Monthly Income × 0.28
Max Total Debt (36% rule) = Monthly Income × 0.36
Max Housing After Debts = Max Total Debt - Monthly Debts
Max Monthly Payment = Min(28% rule, 36% rule - debts)
Max Loan = Payment × [(1+c)^n - 1] / [c × (1+c)^n]
Where c = monthly interest rate (annual rate / 12), n = total payments (years × 12)
Max Home Price = Max Loan + Down Payment
Front-End DTI = Max Monthly Payment / Monthly Income × 100
Back-End DTI = (Max Monthly Payment + Monthly Debts) / Monthly Income × 100
ユースケース
First-time home buyers determining their budget before house hunting
Current homeowners evaluating whether they can afford to upgrade
Comparing affordability at different down payment levels
Understanding the impact of interest rate changes on buying power
Pre-qualification preparation before meeting with a mortgage lender
主な利点
Get an instant home affordability estimate based on your finances
Understand the 28/36 DTI rules lenders use to qualify you
See a complete monthly payment breakdown including taxes and insurance
Compare conservative, moderate, and aggressive price ranges
Free on any device, no downloads or sign-up required
プロのヒント
Get pre-approved by a lender for the most accurate affordability number
Improve your credit score before applying to get a better interest rate
Consider a larger down payment to avoid PMI and increase buying power
Factor in home maintenance costs (1-3% of home value annually) beyond the mortgage
Use the conservative estimate if your income is variable or you have other financial goals
避けるべきよくある間違い
Using net income instead of gross income for DTI calculations
Forgetting to include all monthly debt obligations
Not accounting for property taxes and insurance in the budget
Ignoring PMI costs when putting down less than 20%
Overestimating what you can comfortably afford monthly
重要な用語の説明
Front-End DTI: Housing costs divided by gross monthly income
Back-End DTI: All debt payments divided by gross monthly income
PMI: Private Mortgage Insurance required when down payment is below 20%
Principal & Interest: The core mortgage payment excluding taxes and insurance
関連コンセプト
Mortgage Calculator – Calculate monthly payments for a specific home price
Refinance Calculator – Compare your current mortgage vs a refinance option
Rent vs Buy Calculator – Analyze whether renting or buying makes more financial sense
例
You earn $90,000/year ($7,500/month) with $500/month in debt payments and $60,000 saved for a down payment. At 6.5% interest for 30 years: 28% rule = $2,100/month max housing. 36% rule = $2,700 total debt - $500 existing = $2,200 max housing. The lower limit is $2,100. This supports a loan of approximately $333,000. Adding your $60,000 down payment, your maximum home price is about $393,000. Your front-end DTI would be 28% and back-end DTI would be 34.7%.
よくある質問
What is the 28/36 rule for home affordability?
The 28/36 rule is a standard guideline used by lenders. Your housing costs (mortgage, tax, insurance, PMI) should not exceed 28% of gross monthly income (front-end DTI), and your total debt payments (housing + car loans, student loans, credit cards) should not exceed 36% of gross monthly income (back-end DTI). This ensures you can comfortably afford your home payment.
How much down payment do I need to buy a house?
The minimum down payment varies by loan type: conventional loans typically require 3-5%, FHA loans require 3.5%, VA loans require 0% for eligible veterans, and USDA loans require 0% in qualifying rural areas. However, putting down 20% avoids private mortgage insurance (PMI), which can save $100-$300+ per month.
What is PMI and when is it required?
PMI (Private Mortgage Insurance) protects the lender if you default on your loan. It is required on conventional loans when your down payment is less than 20% of the home price. PMI typically costs 0.5% to 1% of the loan amount annually. For a $300,000 loan, that's $1,500-$3,000 per year or $125-$250 per month. You can request PMI removal once you reach 20% equity.
How do lenders calculate how much house I can afford?
Lenders use your debt-to-income (DTI) ratio. They calculate your front-end ratio (housing costs ÷ gross income) and back-end ratio (all debt payments ÷ gross income). Most conventional lenders allow up to 28% front-end and 36% back-end. FHA loans may allow up to 31%/43%. VA loans can go higher with compensating factors. The lower of the two limits determines your maximum housing payment.
Should I use the conservative or aggressive affordability estimate?
The conservative estimate (85% of max) gives you breathing room for unexpected expenses, savings, and lifestyle. The moderate estimate is the standard calculation. The aggressive estimate (115% of max) stretches your budget and leaves less room for other financial goals. We recommend the conservative or moderate range for most buyers, especially if you have variable income or other financial priorities.
How does my credit score affect home affordability?
Your credit score directly affects the interest rate you qualify for, which significantly impacts affordability. A borrower with a 760+ credit score might get 6.5% while a 620 score might get 7.5%. On a $300,000 30-year loan, that 1% difference costs about $200 more per month, reducing your buying power by approximately $30,000. Improving your credit score before buying is one of the best ways to increase affordability.
What monthly debts should I include in the calculator?
Include all recurring monthly debt obligations: minimum credit card payments, car loan payments, student loan payments, personal loan payments, alimony or child support, and any other installment debt. Do not include utilities, groceries, or discretionary spending — those are living expenses, not debt obligations.
How accurate is this home affordability calculator?
This calculator provides a solid estimate based on the standard 28/36 DTI rules used by most lenders. However, actual loan approval depends on additional factors: credit score, employment history, cash reserves, and the specific lender's underwriting guidelines. Some lenders allow DTI ratios up to 43% or even 50% for certain loan programs. Always get pre-approved by a lender for the most accurate picture.
What is the difference between pre-qualification and pre-approval?
Pre-qualification is a quick estimate based on self-reported financial information — it gives you a rough idea of what you might afford. Pre-approval involves a lender verifying your income, assets, credit, and debts — it provides a firm commitment for a specific loan amount. Pre-approval is much stronger when making an offer on a home and shows sellers you are a serious buyer.
How do property taxes affect home affordability?
Property taxes are a significant ongoing cost that directly reduces how much house you can afford. They vary widely by location — from 0.27% in Hawaii to 2.49% in New Jersey. On a $300,000 home, a 1.1% property tax rate adds $275/month to your payment. Higher property tax areas reduce your maximum home price because the tax portion eats into your 28% housing budget.
Can I afford a house if I have student loan debt?
Yes, many homebuyers have student loan debt. The key is your debt-to-income ratio. If your student loan payments are manageable relative to your income, you can still afford a home. For example, with $80,000 annual income ($6,667/month), $500/month in student loans, and no other debts, your back-end DTI allows up to $1,900 total debt. After student loans, you have $1,400 for housing — enough for a $200,000-$250,000 home depending on rates and down payment.
