Millionaires Don't Worry About This Credit Card Number

And depending on how you use your credit card, you might not need to, either.

When you're shopping around for a new credit card, there are many factors you can use to compare them and make your pick. Sign-up bonuses. Annual fees. Rewards rates, meaning the amount of cash back, points, or miles a card earns. Spending credits.

Americans at every level of wealth use credit cards, but it turns out that the wealthiest often prioritize different factors when choosing a card. In The Ascent's recent study on how rich Americans use credit cards, there was one number in particular that millionaires were far less likely to worry about.

Little interest in interest rates

Millionaires pay much less attention to a credit card's interest rate, or APR (annual percentage rate). When asked about the most important factor in choosing a new credit card, 40% of Americans with a net worth under $1 million chose the interest rate. Only 26% of millionaires said the same. They're also more likely than non-millionaires to prioritize rewards rates and sign-up bonuses.

This makes sense when you consider that you only get charged credit card interest if you carry a balance. If you pay off your card's statement balance in full every month, the card issuer doesn't charge interest on your purchases. In that case, the interest rate on your credit card doesn't matter, because you're never getting charged interest.

It's presumably easier for millionaires to pay their credit card bills in full. Since they have more money saved, it stands to reason that they're less likely to carry a balance.

But interestingly enough, only about a third of millionaires actually followed that habit. Here's how often millionaires reported that they pay their credit card's statement balance:

• 33.07% pay it every month
• 22.20% pay it not every month, but often
• 24.80% pay it a few times per year
• 19.93% pay it almost never

Over 40% are carrying a balance, and getting charged interest, more often than not. For those millionaires that do carry a balance, interest rates should be a priority.

Does your credit card's interest rate matter?

Even though your credit card's interest rate seems important, it might not be. If you always pay the full statement balance, your card's interest rate doesn't matter. You'll never be charged interest, so it won't come into play.

This is a great habit to follow, because you can take advantage of the perks that top credit cards offer, like rewards and building your credit. And you'll do that while avoiding the drawbacks, namely credit card debt and expensive interest charges.

The only time credit card interest rates matter is when you can't pay off your balance. In this situation, your best bet is to avoid interest charges entirely with a 0% intro APR card. This type of credit card has a 0% APR for an introductory period, such as 12 or 15 months. The intro APR may apply to purchases, balance transfers, or both.

So, if you have some big purchases to make and you know you'll need some time to pay them off, get a card with a 0% intro APR on purchases. If you're currently paying down debt, check out balance transfer credit cards that you can use to refinance that debt at a 0% intro APR.

Millionaires aren't the only ones who don't need to worry about interest rates. If you get into the habit of paying off your credit card bill, you can focus on other factors when picking a card, like the benefits offered.