Lenders look at two ratios: front-end (just your housing payment vs. income) and back-end (all your monthly debts vs. income). Below 43% back-end is the sweet spot for most conforming loans.
Lenders use specific definitions of "monthly debt" — minimum payments only, some excluded if <10 months remaining, certain installment debts excluded with sufficient assets. This calculator gives you a ballpark; we'll do the precise calc when you apply.