Cosigner Loan Affordability Calculator

Enter both parties' monthly income and debt plus the new payment to check combined DTI.

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

When a borrower's income alone doesn't qualify for a loan, lenders can combine the borrower's and cosigner's income and monthly debts into a joint debt-to-income (DTI) ratio, typically checked against the roughly 43% qualifying threshold used in conventional loan underwriting — the benchmark behind the CFPB's Qualified Mortgage rule.

A cosigner is legally on the hook for the debt if the primary borrower defaults, so lenders evaluate the combined household's capacity to repay, not just the applicant's alone. This calculator is used by loan applicants and their prospective cosigners, loan officers, and financial advisors pre-qualifying an application before a formal credit check.

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