Mac Miller is not your typical 18-year-old.

On a weekday afternoon, while most of his peers were in school or at work, Miller (born Malcolm McCormick) was giving an interview over the phone while recovering from playing a show in his hometown of Pittsburgh the night before on a bill with his hip-hop mentor and Rostrum Records label mate Wiz Khalifa.

This week Miller is headed to Cambridge, where he’ll play two nights at the Middle East. Both shows are sold out, the result of the buzz generated by his free Internet mixtape “K.I.D.S.,” which has passed the 100,000 download mark and earned him national exposure.

Success has come rapidly for Miller, who was still in high school earlier this year. But even then he was working hard on his rap skills.

“When I was backstage at the show last night, this dude asked me, ‘So what did you do in high school?’ ” Miller said, his voice hoarse from the previous night’s exertions. “Because in Pittsburgh, there are the high school hangouts. Some people went to this place, some people when to another place. He asked me, ‘Where were you?’ I told him, ‘I was in the studio. Why do you think I’m here right now?’ What’s played such a big role in my success is that I’m such a hard worker.”

“K.I.D.S.” (stands for Kicking Incredible Dope (expletive)) is full of tongue-in-cheek raps about parties, girls and growing up. It catapulted Miller onto tours with such veterans as Massachusetts natives Statik Selektah and Termanology and made him the reluctant new face of “frat rap,” a genre popularized by young, suburban-raised white males like Asher Roth and Cambridge-born Sam Adams.

“As far as frat rap, I just don’t think that’s really me,” Miller said.. “I don’t even know what it really is. I’ve been categorized in the frat rap thing strictly because I’m white. But if you listen to my music, a lot of it isn’t the best party music. A lot is chill vibe music. Because of that, I’ve been categorized as stoner rap. Everyone wants to categorize, but I’m doing what I can to make my own category of music.

“I know Asher (Roth) wouldn’t call himself frat rap. He likes to be on some hip-hop cool (expletive). Sammy (Adams) is working on some dubstep-style music with his stuff, which is a genre of its own as well. I’m trying to get something together with my career where I have a genre of my own and my own category.”

Miller has also benefited from his friendship with rising star Wiz Khalifa, who Miller calls a “big brother.” But he’s quick to point out that he can stand on his own two feet.

“I don’t want to come up as only known as Wiz Khalifa’s little homey in music,” Miller said. “We’ve talked about this countless times, about me carving my own path and doing my own thing with my own fan base. The one thing that’s really important, and why Rostrum is Rostrum, is that everyone wants to carve their own path.”

Which Miller plans to do the only way he knows how.

“I’m in the studio all night, every day,” he said. “If I’m not in the studio it’s because I’m on the road. If I’m not doing either of those it’s because I’m paralyzed and I can’t move. But basically, that’s all I do. It’s all I’ve ever done. That’s one of the reasons that Rostrum signed me is because I was willing to work so hard. I’m not going to stop working that hard just because I got a little recognition. Now it’s time to work harder than ever.”

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