Basically, how much debt do you have vs. how much access to debt do you have. The theory is that having a $500 credit card balance on a card with a $500 limit is bad. But a $500 balance on a $20,000 limit card is good. But a complication is that if you have a card you don't use, the credit limit of that card bumps up your available credit. Cancel that card, and you throw that unused available credit away and your score goes down. From a credit score perspective, it really is better to have a bunch of credit cards open that you rarely use (use them just enough to keep them as active accounts, and that's it) than to only have one card that you use a lot. Using just one card (or none at all, for that matter) is probably better for your personal financial management, but not for your credit score.