A business owner I know borrowed four hundred thousand dollars to buy equipment. The bank approved it, he signed quickly, and nineteen months later he was back in the bank struggling. His equipment payment plus his existing debt had pushed his monthly obligations to around twenty-eight thousand dollars. His business generated about thirty-two thousand a month in operating income. In a good month, he cleared the bar. In a slow month — and there are always slow months — he couldn't cover his loan payments. Nobody had walked him through what his numbers actually meant before he signed.
The number that would have told him is the debt service coverage ratio, or DSCR. It's the single most important ratio your lender looks at, and most owners have never calculated it. The math is simple: take your net operating income — your operating profit before interest and depreciation — and divide it by your total annual debt payments, principal and interest combined. If your operating income is $384,000 and your annual debt service is $336,000, your DSCR is 1.14. That means you're generating just fourteen percent more than you need to cover your debt. It sounds fine. It isn't comfortable. A 1.14 means a fourteen percent dip in income puts you in default territory.
Lenders generally want to see a DSCR of at least 1.25, and many loan agreements actually require you to maintain a minimum ratio for the life of the loan. That requirement is called a covenant, and it's buried in the loan agreement, not the term sheet. Here's the part that catches people: you can be current on every payment and still be in technical default if your DSCR slips below the covenant. I've watched a business get a call from the bank — not about a missed payment, but about a covenant breach discovered during a routine review. That conversation led to a loan modification, fees, and a higher interest rate. All of it avoidable if the owner had been tracking the number himself.
The bank's job is to decide whether you can repay a loan. Your job is to decide whether you should take it — and those are different questions. Before you borrow, calculate your current DSCR. Then calculate what it would be after you add the new debt payment. Ask yourself what revenue decline would push you below 1.25, and whether that decline is realistic for your business in a bad quarter. If you already have loans, pull the agreements and find every covenant, then calculate your buffer above each threshold. Run these numbers before your banker does. Walking into a loan meeting already knowing your ratios doesn't just protect you from a bad decision — it signals that you run your business with discipline, and that tends to get you better terms.