It’s official: 2012 will go down as the year “The Big Bang Theory” exploded.

Already one of TV’s most popular shows, the geek has really hit the fan, as encore airings are performing as well as any original series, and on multiple channels.

Nielsen issued numbers last week that showed the Warner Bros. half-hour was syndication’s most-watched program of the week for the eighth time in 10 tries. Its average nightly audience of 8.97 million viewers for the week of July 2-6, a big spike from the 7 million or so it was averaging in its first syndication month last fall, put it ahead of usual top-dogs like “Judge Judy” and “Wheel of Fortune.”

But the total-viewer tally tells only part of the story.

The show was easily the week’s top syndicated program among adults 18-49, drawing a 3.2 rating (roughly 4.1 million viewers in that bracket). The next closest programs in that demo were “Family Guy” (2.5) and “Two and a Half Men” (2.4).

In primetime last week, a CBS repeat of “Big Bang” was the No. 1 series in adults 18-49 with a 2.8 rating (tying NBC’s “America’s Got Talent”) — up a whopping 40% from the same night a year ago. Among the shows it beat out are original segs of summer stalwarts like “The Bachelorette,” “Big Brother” and “Hell’s Kitchen.”

Nominated for a best comedy Emmy last week, “Big Bang” is coming off a season on CBS that saw it emerge as TV’s most-watched laffer for the first time, with nearly 16 million viewers.

And in cable, 16 primetime airings of “Big Bang” vaulted TBS to a No. 1 ranking among all cable networks in 18-49.

A 10:30 p.m. Wednesday repeat of “Big Bang” on TBS (with a 1.5 rating in 18-49) beat out all other ad-supported scripted cable series for the week, with the exception of AMC’s return of “Breaking Bad” — an impressive feat, since cable is at its peak for originals in the summer.

Indeed, whoever subscribes to “Theory” these days is getting plenty of bang for their buck.