A rewards card can still be expensive debt if interest charges outrun the value of the points or cash back.
The Consumer Financial Protection Bureau says APR is the price of borrowing, and that basic rule matters more than a 1% to 5% reward rate for anyone carrying a balance.
Cash back can feel like free money. But on a credit card, it stops being a real benefit the moment interest costs more than the reward earns. That is the central tradeoff in the cash back vs interest debate, and it is more straightforward than many marketing pitches make it sound.
According to the Consumer Financial Protection Bureau, a credit card’s APR is the price you pay for borrowing money. On most cards, purchases avoid interest only when the balance is paid in full by the due date. Once a cardholder revolves a balance, the economics can flip quickly: a small reward rate sits on top of a much larger borrowing cost.
The decision rule is simple
If the interest you pay is greater than the rewards you earn, the card is costing more than it is giving back. That sounds obvious, but it is the clearest way to judge whether a rewards card is helping or hurting.
The catch is that there is no universal break-even APR that works for everyone. Interest charges depend on the balance, how long it is carried, the card’s terms, and how the issuer calculates interest. The CFPB says many issuers calculate interest daily using an average daily balance, which means the cost is not simply APR divided by 12 in every real-world case.
A worked example, with assumptions
Assume a cardholder makes a $2,000 purchase on a card that offers 2% cash back and has a 24% APR. The reward is easy to see: 2% of $2,000 is $40. Now assume the cardholder does not pay the statement balance in full and carries that debt for several months.
If that balance remains unpaid long enough for interest charges to rise above $40, the reward has been wiped out. At that point, the cardholder is no longer coming out ahead from the rewards feature. The exact timing will vary because issuers often use daily periodic rates and average daily balances, and because payments reduce the balance over time. But the framework does not change: compare annual or multi-month rewards earned with actual interest paid on statements.
That is why reward rate is secondary for revolvers. A jump from 1% to 3% cash back may look meaningful in an ad, but it is small next to interest on an unpaid balance.
Why the grace period matters
The CFPB defines a grace period as the time between the end of a billing cycle and the payment due date. During that window, most cards do not charge interest on purchases if the balance is paid in full and on time. For cardholders who always pay in full, cash back is more likely to function as a true rebate.
For cardholders who do not, the loss of the grace period can make new spending more expensive than expected. The CFPB says that if you lose the grace period by failing to pay in full, interest can apply not only to the unpaid amount but also to new purchases, starting from the date those purchases are made. That means a rewards card balance can become costlier even if the reward rate itself has not changed.
Important exceptions
Promotional APR offers can change the picture. A temporary 0% purchase APR, for example, may allow a cardholder to earn rewards without immediate interest on that balance, though the promotional window, deferred-interest risks, and post-promo rate still matter. Balance-transfer offers can also work differently, and cash advances generally do not get the same grace-period treatment as purchases.
The broader point is not that rewards are useless. It is that rewards matter after interest is under control. For households comparing cards, the practical order of operations is clear: check the APR, understand the grace period, review how interest is calculated on the statement, and estimate how fast the balance will be paid down. Only then does the advertised cash-back rate tell you what the card is really worth.