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Ratio questions lose points on the base, not the arithmetic: gross income for DTI, the lower of price and value for LTV. The defaults are the worked examples from our math guide.
The ratio limits a loan must meet depend on the program and the lender's guidelines, so this calculator shows the ratios and leaves the limits to the question.
Using net (take-home) income instead of gross. Counting living expenses such as utilities as debts. Dividing by the purchase price when the appraisal came in lower: $270,000 on a $310,000 price and a $300,000 appraisal is 90% LTV, not 87.1%.
For study and general guidance only, not legal or lending advice. Figures checked 11 Oct 2026 against MLO Prep mortgage math guide. Rules change; confirm with the source before relying on a result.
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The front-end ratio counts only the housing payment (PITIA). The back-end ratio adds every recurring monthly debt, such as car, credit card and student loan payments. Both divide by gross monthly income.
On a purchase, LTV uses the lesser of the purchase price and the appraised value.
Combined loan-to-value: the total of every lien on the property, such as a first mortgage and a second mortgage, divided by the property value.