Mortgage affordability is determined primarily by your debt-to-income (DTI) ratio — the percentage of your gross monthly income that goes toward debt payments. Lenders use two key ratios: the front-end ratio (housing costs only, typically capped at 28–31%) and the back-end ratio (all debt including housing, typically capped at 36–43%). Our calculator uses industry-standard DTI thresholds to estimate the maximum home price you can qualify for given your income, existing debts, and down payment.