NEW YORK (AP) ― In just two years, English singer Ed Sheeran has gone from the small stage to the big league.

The 22-year-old earned a gold album with his 2011 debut, “+,’’ and his Top 20 hit, “The A Team,’’ was nominated for song of the year at the Grammy Awards, but his biggest achievement comes this week: He is performing three shows at the famed Madison Square Garden.

Sheeran is part of a breed of newer and lesser known acts who are able to sell out top venues, even if they aren’t pushing millions and millions of albums and singles like Eminem and Justin Timberlake, or dominating with chart-topping tracks and radio airplay like Katy Perry or Rihanna.

Pop-rock band Passion Pit, who released their sophomore album last year, sold out MSG earlier this year, and the Weeknd, the eerie, reclusive R&B singer, performed two sold-out nights at Radio City Music Hall to a feverish crowd this month. Gotye, though he had last year’s biggest hit with “Somebody That I Used to Know’’ and a gold album, performed at the 9,000-seat Radio City after playing NYC’s Terminal 5, with a third of that capacity, six months prior. And the English indie band the xx, critically acclaimed but fairly unknown outside of the music industry, performed two shows at Radio City last month.

“We played the Mercury Lounge like a year and a half ago, and to go from like a 150-capacity venue to, I think it’s 18,000 at MSG _ it’s cool,’’ said Sheeran, who will play his first sold-out MSG on Tuesday.

For that he might thank his fans on Twitter ― where Sheeran has more than 8 million followers ― and the support of Taylor Swift and One Direction, whom he opened for and collaborated with.

“With social media playing an increasing role, it’s possible for an artist to go from totally unknown to significant enough popularity to sell an arena like Madison Square Garden,’’ said Gary Bongiovanni, the president and editor-in-chief of concert trade magazine Pollstar.

Omar Al-Joulani, Live Nation’s vice president of touring, echoed Bongiovanni’s theory.

“(It) definitely feels like artists can have a quicker run to selling out more venues mostly because it’s easier to get noticed these days because you can go straight to your fan base,’’ he said. “Whether they have radio or not, (these artists) have very big online followings.’’

Al-Joulani added that while other emerging acts have sold top venues in the past, “it just seems to be happening more often now.’’

Imagine Dragons and fun. ― whose mainstream breakthroughs are recent though they both formed in 2008 ― have gone from small theaters to top-billing venues in a year, aided by back-to-back hits and platinum-selling albums. Imagine Dragons, whose hits include “Radioactive’’ and “It’s Time,’’ will launch an arena tour in February that includes dates at the American Airlines Center in Texas and the IZOD Center in East Rutherford, New Jersey.

Moderate ticket prices are another reason these musicians are able to sell out venues: Imagine Dragon’s tickets won’t price higher than $70 ― and that includes service and facility fees. In comparison, upcoming shows for Justin Timberlake and Cher at the IZOD can go as high as $224 and $174, respectively.

“The hardest thing to do as an artist ... is when you try to sell an appreciable number of more tickets than you have in the past while taking the ticket price to a new level,’’ said Al-Joulani, who books shows for Imagine Dragons, Jay-Z and Swedish House Mafia. “What we’ve done with Imagine Dragons is we’ve upped the venue size, but we haven’t gone crazy with the ticket price.’’

Sheeran, who is working on his sophomore album, will also perform at MSG on Friday and Nov. 7; the most expensive ticket is $64.10 with fees. While the singer-songwriter is charting his own success, others have given him a boost: He was the opening act on the North American leg of Swift’s massive “Red’’ tour and collaborated with the country-pop star on the recent Top 40 hit, “Everything Has Changed.’’ Sheeran also co-wrote songs on both of One Direction’s albums and has hit the road with the boy band.

“In (Sheeran’s) case, for everyone ― the promoter, manager, his agent ― it was a gut instinct. The time was right,’’ said Melissa Ormond, the entertainment president at the Madison Square Garden Company, which owns MSG and Radio City.

While these budding acts have the opportunity to play large venues, Bongiovanni advises caution.

“They can demonstrate the commercial potential and sell tickets, but can they do a show that will leave people satisfied and wanting more?’’ he said. “You get offered a lot of money to play these big halls and it really takes someone with good management and good instincts to say, `I’m not ready at this point.’’’

Imagine Dragons’ manager said he and the band have had conversations about where and when to play particular venues and territories.

“We’re not trying to play the biggest rooms we can and we wouldn’t do it because we know we can sell it out. It’s not about trying to make as much money as we can,’’ said Mac Reynolds. “It’s about looking at the trajectory and where we’re at and what feels appropriate.’’