How do you estimate DSCR for a rental property before making an offer?

When you’re screening a rental property, how do you estimate its DSCR before you ever talk to a lender? I usually start with the rent, subtract taxes, insurance, maintenance and vacancy to get an NOI estimate, then divide by the annual debt service on the loan amount I’m considering. But lenders seem to calculate it differently — some use market rent instead of the actual lease, some include reserves, and the ratio swings a lot depending on the rate. How do you run your own estimate so it lines up with what a lender will actually see? Do you target a specific DSCR buffer above the lender minimum?