Home Affordability Calculator

What the 28% housing ratio means for your budget

The tool anchors its comfortable price calculation on the standard guideline that housing costs — principal, interest, taxes, and insurance combined — should not exceed 28% of gross monthly income. On a $90,000 annual income that is $2,100 a month. Sounds simple, but the number shifts fast once you add property taxes and insurance back in. A $300,000 home at 7% for 30 years carries principal and interest of about $2,000 a month before a dollar of taxes or insurance.

That is why the PITI output matters more than the loan payment alone. A buyer stretching to a $320,000 home in a high-tax county can end up $400–500 above a comfortable PITI even at the same loan amount. The calculator handles this transparently: enter your expected property tax rate and annual insurance, and it builds a full monthly figure rather than letting you anchor on the loan payment and fill in the rest with optimism.

How your existing debts reshape the ceiling

Monthly Debts — car loans, student loans, credit card minimums — are the variable most buyers underweight. Lenders typically allow a total back-end DTI of 43–45%, meaning your new mortgage PITI plus all existing monthly debt payments must fit within that percentage of gross monthly income. If you have $600 a month in car and student loan payments on a $7,500 gross income, you are already at 8% DTI before you borrow a dollar for a house. That $600 alone cuts the maximum loan by roughly $75,000–$90,000 compared to a buyer with no debts and the same income.

The tool shows you the DTI calculation so you can see exactly which debts are doing the most damage. Sometimes it is more effective to pay off a $180-a-month car loan before applying than to save another $5,000 toward the down payment. The numbers will tell you which move matters more in your specific situation.

Down payment: how much actually changes your monthly cost

Every extra dollar in down payment does two things: it lowers the loan principal and, past the 20% threshold, it eliminates private mortgage insurance. PMI typically runs 0.5–1.5% of the loan annually — on a $280,000 loan that is $1,400–$4,200 a year, or $117–$350 a month added to your PITI. The calculator accounts for this by treating a sub-20% down payment as a signal that PMI should be factored into affordability guidance.

The down payment field also interacts directly with your bank approval number. A larger down payment lowers the loan-to-value ratio, which can open better rate tiers with some lenders. If you are sitting at 19% down, the math on whether to wait and save that last percentage point is worth running before you start making offers.

Loan term choice and its real cost

A 15-year mortgage at the same rate as a 30-year costs significantly more each month but far less over time. On a $300,000 loan at 7%, the 30-year payment is roughly $2,000 in principal and interest; the 15-year is about $2,700. The 30-year buyer pays roughly $420,000 in total interest over the life of the loan; the 15-year buyer pays around $180,000. That $240,000 difference is real money even accounting for inflation.

The Loan Term input lets you toggle between the two and see how the monthly PITI shifts. Many buyers default to 30 years for affordability reasons, which is a legitimate choice — but knowing the interest cost difference is useful before you commit. Some operators buying investment property intentionally choose 30 years to keep monthly costs low and cash flow positive, while buyers of a primary residence often benefit from modeling both.

When the comfortable price and max approval diverge sharply

The most useful output this tool produces is the gap between the recommended comfortable price and the max the bank will approve. In hot markets, those two numbers can be $80,000–$150,000 apart. A buyer approved for $480,000 who has a comfortable price of $340,000 faces a real decision about how aggressively to bid.

The calculator does not tell you which to choose — that depends on your income trajectory, savings cushion, and risk tolerance. What it does is make the trade-off explicit in dollar terms. Buying at max approval on a dual income with one partner planning to leave work in two years is a very different risk profile than buying at max on a single stable salary with three years of reserves. Run both scenarios before walking into a listing.

Home Affordability Calculator vs. the alternatives

How to use it

1. Enter Annual Gross Income (before taxes) — use combined household income if buying jointly.
2. Enter Monthly Debts — include all minimum payments: car, student loans, credit card minimums.
3. Enter Down Payment Saved — the cash you have available today, not a target.
4. Set Mortgage Rate (%) and Loan Term (years) to match current market rates or what you have been quoted.
5. Read the Recommended (Comfortable) Price, the Max the Bank Will Approve, and the PITI at comfortable price — then compare the gap.

Who it's for

• First-time buyer reality-checking their price range — A buyer earning $75,000 with $1,100 in monthly debts and $45,000 saved enters their numbers and discovers their comfortable price is $280,000, while their bank will approve up to $360,000 — useful context before touring $350,000 listings.
• Dual-income couple planning a timeline — A couple with $130,000 combined income and $18,000 saved runs the calculator to see how their comfortable price jumps from $310,000 to $395,000 if they hit $40,000 saved in 18 months — giving them a concrete savings target.
• Buyer deciding whether to pay off debt first — An owner-to-be with a $450/month car payment models what removing that debt does to max approval — sees it adds roughly $55,000 in purchasing power and decides whether paying it off is worth delaying the purchase.
• Self-employed buyer stress-testing different income figures — A freelancer whose gross income varies between $80,000 and $110,000 runs the calculator at both figures to see the floor and ceiling of their comfortable range before approaching a lender.

Key terms

PITI

The full monthly housing payment: Principal, Interest, Taxes, and Insurance. The number to use when comparing what you can afford — not just the loan payment.

Debt-to-Income ratio (DTI)

Total monthly debt obligations divided by gross monthly income, expressed as a percentage. Lenders use this to determine how much of your income is already committed before adding a mortgage.

Comfortable price

The purchase price at which your total PITI stays within 28% of gross monthly income — the standard guideline for a payment you can sustain without financial stress.

Private Mortgage Insurance (PMI)

A monthly premium required on most conventional loans when the down payment is less than 20% of the purchase price. Typically 0.5–1.5% of the loan annually until sufficient equity is reached.

Sources & further reading

• CFPB Owning a Home — affordability and DTI guidance — The CFPB's Owning a Home hub publishes home affordability guidance recommending total debt-to-income ratios at or below 43% under the Qualified Mortgage rule, and provides closing-cost and PITI worksheets aligned to TILA-RESPA disclosure requirements.
• Fannie Mae Research and Insights — Home Purchase Sentiment Index — Fannie Mae's Home Purchase Sentiment Index and monthly Economic and Housing Outlook quantify home affordability headwinds, tracking the share of consumers who say it is a good time to buy and modeling 30-year fixed mortgage rate scenarios for purchase-price ceilings.
• Freddie Mac Research — Primary Mortgage Market Survey — Freddie Mac's Primary Mortgage Market Survey publishes the weekly average 30-year fixed mortgage rate used directly in home affordability calculations, and its Research division models how each 1-percentage-point rate move shifts qualifying loan amounts by roughly 10%.
• NAR Research and Statistics — Housing Affordability Index — The National Association of REALTORS publishes the Housing Affordability Index (HAI), where a value of 100 means a median-income family has exactly enough income to qualify for a mortgage on a median-priced home assuming a 20% down payment and 25% qualifying ratio — the benchmark for home affordability trend analysis.
• HUD Buying a Home — FHA loan limits and affordability rules — HUD's Buying a Home portal documents FHA home affordability standards, including the 31% front-end and 43% back-end DTI maximums, 3.5% minimum down payment for FICO 580+, and annually updated FHA loan limits that cap qualifying purchase prices by county.