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How a mortgage affordability calculator estimates how much house you can buy
Home affordability is about much more than the sticker price. Total monthly housing combines principal and interest (your mortgage payment), property tax, homeowners insurance, and any HOA or condo fees — together known as PITI plus HOA. A mortgage affordability calculator solves the problem backward: starting from your income and existing monthly debts, it applies a maximum debt-to-income ratio and works out the home price where PITI plus HOA still fits inside that limit.
The standard guideline is the 28/36 rule. Front-end ratio (housing only) should be 28% or less of gross monthly income. Back-end ratio (housing plus other debt payments) should be 36% or less. Many lenders allow back-end DTI up to 43% for qualified mortgages, and some government-backed loans permit higher ratios. The DTI percentage you choose in this calculator directly drives the affordable home price it returns.
Three other inputs strongly influence the result: down payment lowers the loan amount and interest you pay; interest rate sets monthly principal-and-interest cost; and property tax rate is multiplied by the home price every year. Even a 1% tax rate adds noticeable monthly cost on a $400,000 home. To plan further, compare your existing debt with our Debt-to-Income Calculator, estimate the actual mortgage payment with our Mortgage Calculator, and check how a new loan would change your DTI with the Loan Payment Estimator. To free up monthly budget room, try our Budget Planner. And remember — better credit usually unlocks better rates, so read how credit scores are calculated and watch your credit utilization.
Important: This calculator is for educational estimates only and is not mortgage, lending, legal, tax, or financial advice. It does not represent loan approval. Always verify final numbers with a licensed mortgage professional before making purchase decisions.