Example: If the borrower owes $1,500 in credit card payments and has a gross monthly income of $3,000, his DTI ratio would be 50%. But if the borrower owes $1,500 in payments and has a gross monthly income of $2,000, his DTI ratio would be 75%. Both a 50% and 75% DTI ratio would be too high for most lenders, as a DTI ratio of 43% is generally the cutoff for conventional mortgages. All other factors aside, the higher the DTI ratio, the less likely the borrower will be able to afford a monthly payment, hence the more risky it is for the lender.