A lot of experts will tell you that buying a new car is a terrible investment. But buying a new car can be important or valuable to you for other reasons, says Ramit Sethi, the best-selling author of "I Will Teach You to be Rich."
"You might have heard a lot of people telling you don't ever buy a new car, [it's] a huge waste of money," Sethi says. "I disagree with that. I think there are a lot of reasons to buy a new car."
Maybe you want something reliable that you won't have to constantly take in for repairs. Maybe you want the latest safety or fuel efficiency technology. Or maybe you just want to reward yourself by buying something shiny and exciting.
Whatever your reasons, if you are considering buying a new car, Sethi tells CNBC Make It, there's one big question to ask yourself: Can you afford it?
Running the numbers to determine the answer to that question can be complicated, so Sethi offers what he calls the "20-4-10 rule." Here's how it works.