Determining the ability to repay debt on time each month is important to a lender when making a loan decision. A debt-to-income ratio, or DTI, is one of the tools lenders use to determine your ability to pay. You calculate two things to figure out the percent: monthly income and existing monthly credit expenses. Lenders typically use verified gross monthly income, your pay before taxes, when determining an ability to repay. Gross monthly income includes a paycheck from an employer, plus any money you may receive in government aid, child support or pensions. After totaling gross income, the lender will determine the amount of debt the applicant pays monthly. Typically, lenders use a credit report to identify the applicant’s debts. Some examples include car payments, student loans and credit card balances.