Dual Income Housing Ratio Calculator

The front-end ratio divides your total monthly housing cost — mortgage or rent plus property tax, insurance, and HOA dues converted to monthly — by combined gross monthly income, and lenders typically want this at or below 28%. The back-end ratio adds your other monthly debts (car loans, student loans, credit cards) on top of housing before dividing by the same income figure, and lenders typically want that at or below 36%, since it captures your full debt burden rather than just housing.

Because the calculator combines both partners' incomes to compute the ratios and maximum affordable price, a couple can qualify for — and be approved for — a home that only looks affordable when both incomes hold steady. If one income is less stable, such as commission-based work, contract work, or dependence on a single employer, rerunning the calculator with only the more reliable income shows whether the housing payment would still be manageable if that other income disappeared.

It takes your maximum affordable monthly housing payment (28% of combined gross monthly income), subtracts the monthly property tax, insurance, and HOA amounts to isolate the portion available for principal and interest, then reverse-amortizes that payment into a loan amount using the standard mortgage formula at a fixed 6.5% rate over a 30-year term. Because it assumes that specific rate and term rather than your actual quote, and doesn't factor in your down payment, treat the result as a rough ceiling rather than a firm pre-approval number.

This value is your maximum affordable housing payment at the 28% guideline minus your actual total monthly housing cost. A positive number means your current housing cost is under the 28% guideline with room to spare, while a negative number means your current housing payment already exceeds what the 28% rule would recommend for your combined income, even before counting other debts in the back-end ratio.