The finale of CBS’ “The Big Bang Theory” went out with a bang in Thursday’s ratings.

The hourlong airing of back to back episodes garnered a substantial 3.1 rating in the key 18-49 demographic and was watched by just under 18 million total viewers. For comparison, the “Big Bang” spinoff “Young Sheldon” came in second on Thursday night with a 2.2 rating and 13.7 million viewers for its season finale, followed by a large drop-off to the “Grey’s Anatomy” season finale, which drew just under 6 million total viewers and a 1.3 rating. The finale also topped the other main demographic of 25-54 (4.7).

That initial rating is the show’s highest since January, 2018, and represents the highest-rated episode of “Big Bang”‘s twelfth and final season by far, while the total viewership figure is the highest the show has produced since September, 2015. The previous season 12 high was 2.57 for the February 7 episode, and the average for the season to-date was 2.2 prior to last night’s finale.

“Big Bang Theory” is the first show to end its run as TV’s top series since the final season of “Seinfeld” aired in 1998.

The “Big Bang Theory” farewell special which aired after “Young Sheldon” at 9:30 p.m. also did extremely well for CBS, coming in at a 1.8 rating and 11.8 million total viewers.

The finale also delivered a 12.2 household rating and 22 share, an impressive live turnout by today’s linear TV viewing standards. It marked a 34% increase in the show’s metered market average for the season.

The “Big Bang” bump boosted “The Late Show with Stephen Colbert” to a blockbuster 3.8 household rating for the night. Colbert’s featured an extended interview with the cast of “Big Bang.”

“Big Bang”‘s massive ratings helped CBS to a handy victory on the night. The network finished with an average rating of 2.0, more than doubling its competitors figures, as ABC came in at a 0.8 across the night and NBC at a 0.6.