WHAT’s the magic behind the amazing appeal of plus-size star MELISSA McCARTHY?

She’s won an Emmy, sold more than $1 BILLION worth of movie tickets worldwide, and she’s kicking man-butt at the box office with her new comedy “The Heat.”

Now, psychological experts are sum­ming up McCarthy’s appeal in two simple words – she’s everywoman!

“Audiences love Melissa because she doesn’t let her physical imperfections stop her from getting what she wants in life,” Dr. Carole Lieberman, a Beverly Hills-based celebrity psychiatrist, told The ENQUIRER. “She’s tough, she’s funny, she’s smart and she refuses to let the fact that she doesn’t look like Bar­bie get her down. Women relate to her struggles and are inspired by how well she overcomes them. She’s everywoman.

“Men like Melissa too, BECAUSE with her, what you see is what you get.”

Dr. Lillian Glass, author and media personality, told The ENQUIRER: “Melissa is popular because she looks like what America looks like right now.

“She’s not your typical stick-figure movie star. People and actors that are a little overweight are the new aesthetic. Weight does not indicate how people re­late to you, as Melissa is clearly proving.

“Personality trumps everything. That’s why Melissa will be a big star for years to come.”

Audiences and critics agree, with McCarthy’s first regular TV gig on “Gilmore Girls” leading to a starring role on the hit sitcom “Mike & Molly” and a 2011 Emmy.

But the former stand-up comic really hit the big-time with an Academy Award nomination for her hilarious break­out performance in the 2011 comedy “Bridesmaids,” which grossed a whop­ping $288 million worldwide, including $169 million in the U.S.

That second-banana role led to a starring slot opposite Jason Bateman in “Identity Thief,” a sleeper hit that stunned industry insiders when it brought in $174 million worldwide.

But the 42-year-old actress – who has two young daughters with her “Bridesmaids” co-star Ben Falcone – proved she’s the gold standard when “The Heat,” her comedy with Oscar winner Sandra Bullock, beat the big boys at the box office.

With a $39 million opening in June, “The Heat” easily won its face-to-face standoff against “White House Down” with Oscar win­ner Jamie Foxx and “Magic Mike” man-candy Channing Tatum, which only scored $24.9 million. “The Heat” also scorched mega-star Johnny Depp’s $29.2 million open­ing in “The Lone Ranger.”

“Melissa is on her way to be­coming one of this town’s biggest stars and top earners,” noted a Hollywood insider.

“After ‘Bridesmaids,’ she was thought of as the ‘go-to’ co-star for bigger names, but now she’s considered as THE star of her future projects. Sandra Bullock should be thanking Melissa for making ‘The Heat’ such a huge hit!”