Although there were two title matches at UFC 187, and it was generally considered the deepest show so far this year, the prelim numbers were slightly below average with 780,000 viewers.
Pay-per-view prelims on FS 1 average about 800,000 viewers, but there is a wide variation. While not a perfect predictor, the shows that do the strongest pay-per-view numbers do the best ratings in most cases. The opposite is also usually the case. So these numbers don't indicate a blockbuster pay-per-view number.
The show was up from the previous month, which did 710,000 viewers for the prelims before UFC 186, the show headlined by Demetrious Johnson vs. Kyoji Horiguchi. But it was down from the 1,003,000 viewers in the prelims for UFC 185, headlined by Anthony Pettis vs. Rafael dos Anjos.
The viewership was probably hurt by going against the Houston Rockets vs. Golden State Warriors NBA playoff game, which did 5,676,000 viewers.
It was up 12 percent from last year's Memorial Day weekend prelims, which did 697,000 viewers. But that was a show headlined by T.J. Dillashaw's bantamweight title win over Renan Barao, with a much less attractive overall night of fights.
The peak rating for the prelims was 969,000 viewers for the final rounds of the John Dodson win over Zach Makovsky, a bout where the potential next challenger for Johnson's flyweight title could have been determined.
The pay-per-view post-fight show on FS 1, airing from 1 a.m. to 2:30 a.m. did 118,000 viewers.
Aside from the NBA game, and shows based around the NBA playoff game, and ESPN Sports Center shows after the game, the UFC prelims were the most-watched sports event on television on Saturday night.
The May 20 episode of The Ultimate Fighter did 340,000 viewers on Wednesday night, and another 172,000 viewers via DVR viewership over the next three days.