Good Debt, Bad Debt, and the Test That Tells Them Apart

"All debt is bad" is comforting, simple, and wrong. "Debt is just a tool" is sophisticated, popular, and also incomplete. The truth sits in between, and there's a single practical test that cuts through the slogans. Once you have it, you can look at any borrowing decision — a mortgage, a car loan, a credit card, a student loan — and judge it on its merits instead of its reputation.

The test: does it buy an asset or an expense?

The cleanest way to sort debt is to ask what the borrowed money turns into.

Debt that buys an appreciating asset or raises your earning power is the kind that can genuinely make you wealthier. A mortgage buys a home that may grow in value and that you'd otherwise pay rent to occupy. A sensible student loan can buy a qualification that lifts your income for decades. Borrowing to start or grow a business that earns more than the loan costs falls here too. The defining feature: the thing you bought has a reasonable chance of being worth more, or earning more, than the debt costs.

Debt that buys a depreciating asset or pure consumption is the kind to minimise. A car loses value the moment you drive it away. A holiday is gone once it's over. Putting everyday spending on a credit card and carrying the balance is the most expensive version of all. None of these are immoral — but none of them make you richer, and all of them cost you interest for the privilege.

Why the interest rate decides the severity

The asset-versus-expense test tells you the type of debt. The interest rate tells you how dangerous it is. A low-rate mortgage on an appreciating home is about as benign as borrowing gets. A high-rate credit card balance on consumption is about as corrosive as it gets — and it's corrosive for a specific, mathematical reason: it's compound interest running against you.

Everything good about compounding when you're saving becomes everything bad about it when you're borrowing at a high rate. The balance grows on itself. This is why credit card debt is the one most financial professionals say to attack first, ahead of almost everything else, including investing. Few investments reliably return what a credit card charges, so clearing that balance is effectively a guaranteed return at that rate.

The grey areas, judged honestly

A car loan is "bad debt" by the asset test, but a reliable car that lets you earn a living is hardly a frivolous purchase — the goal there is to borrow as little as possible, at as low a rate as possible, over as short a term as possible, and not to confuse transport with status. A student loan is "good debt" only if the qualification actually raises your income enough to justify it; the same loan can be wise or ruinous depending on what it buys. The test isn't mechanical. It's a lens.

Putting it to work

Before taking on any debt, run two quick checks. First: does this turn into an asset/earning power, or an expense? Second: what does it actually cost me, using the APR, not the headline rate? (See our explainer on APR vs interest rate.) Good debt at a low rate, used deliberately, is a legitimate wealth tool. Bad debt at a high rate, used by default, is one of the most reliable ways to stay broke while feeling like you're getting by. The label was never the point — the test is.