How to use the DTI ratio and loan limit calculator
American mortgage underwriting asks the same question Korea's debt service ratio rules do: how much of your income already belongs to lenders. The measure here is debt-to-income, and it comes in two flavors. Front-end DTI counts only the housing payment, while back-end DTI adds every other monthly obligation.
The traditional 28/36 guideline says housing should stay under roughly 28% of gross monthly income and total debt under 36%. Separately, the ability-to-repay rules behind qualified mortgages put a widely used ceiling around 43%, which is why the calculator reports your maximum loan at both thresholds.
Enter principal and interest inputs as the loan itself, and put property taxes, homeowners insurance and HOA dues in the escrow field so the housing payment reflects what you actually pay each month. Limits are editable because agency, FHA and portfolio programs each set their own. Figures reflect a September 2026 reference.
This tool is for general reference. Lenders calculate qualifying income differently for bonuses, self-employment and rental income, and compensating factors such as reserves or credit score can move the ceiling. Confirm with a loan officer before making an offer.
Frequently asked questions
It is a long-standing underwriting guideline: housing costs should stay under about 28% of gross monthly income, and all debt payments together under about 36%. Many lenders allow more with compensating factors.
Minimum credit card payments, auto and student loans, personal loans and court-ordered support, added to the full housing payment. Utilities, groceries and insurance that is not escrowed are generally excluded.
The 43% figure comes from the qualified mortgage ability-to-repay framework, but agency and portfolio programs can go higher when reserves, credit score or down payment are strong. Ask your lender which program applies.