The latest "Transformers" movie claimed $100 million in North American ticket sales for its opening weekend, but some in Hollywood say the numbers don't compute.
Paramount Pictures said Monday that its big-budget sequel "Transformers: Age of Extinction" sold $100,038,390 of tickets in the U.S. and Canada from its debut Thursday night through Sunday. That was virtually identical to the $100 million estimate that the Viacom Inc. VIAB +0.42% -owned studio gave Sunday morning and ahead of this year's second-biggest opening, "Captain America: The Winter Soldier" at $95 million in April.
But people with access to the box-office reporting system universally used in Hollywood said that reaching that tally likely involved some not-very-common assumptions on Paramount's part.
Paramount Vice Chairman Rob Moore said: "We believe in the accuracy" of the studio's reported number.
Rentrak Corp.'s RENT +0.11% reporting system has a direct line into the vast majority of theaters in the U.S. and Canada, to track actual ticket sales, but it isn't in quite all of them. To report their "actual" gross the Monday after a film opens, studios estimate the sales at the small number of remaining locations. That figure stands as the final publicly reported opening gross of the movie. Large openings, particularly ones that pass milestone figures like $100 million, are often touted for marketing and publicity purposes by studios.
According to several people with access to Rentrak data, the system provided ticket sales data for about 4,100 of the 4,233 theaters playing "Transformers" in the U.S. and Canada. Together, those theaters sold about $95.9 million of tickets for the film.
Theaters that don't report into Rentrak tend to be small, independent locations that do less business than average. So when calculating their Monday "actuals," studios typically assume that those outlier theaters each gross at most half of what the average theater reporting to Rentrak does.
By that method, "Transformers: Age of Extinction" would have grossed about $97.5 million.
In order for the movie to reach $100 million, the "Transformers" theaters not tracked by Rentrak would have had to gross more than the nation-wide average—a rare though not unprecedented assumption for a studio to make.
Paramount's Mr. Moore said that some of the theaters not included in Rentrak are high-priced digital screens from IMAX Corp. IMAX +2.04% and that others are in Puerto Rico—and that "Transformers" movies perform particularly well with Hispanic audiences.
A knowledgeable person said that of 353 domestic IMAX locations playing "Transformers," only six weren't tracked by Rentrak. Those six tend to be among the lowest-grossing IMAX locations, this person added.
Mr. Moore declined to specify how many theaters in Puerto Rico showed the movie or how many of those were tracked by Rentrak. "These assumptions are consistent with assumptions other studios have made on movies with a larger than normal appeal to Hispanic audiences," said Mr. Moore.
Rentrak declined to comment.
It is common for studios' "actual" box office numbers on Monday to be slightly different—and usually lower—than the estimate issued on Sunday morning. Those "actual" figures are rarely as widely questioned in Hollywood as "Transformers" was on Monday, although scrutiny was high, given the size of the debut.
Paramount will learn the true opening-weekend gross for the film after it receives its cut of ticket sales from theaters in the coming weeks. Mr. Moore said Paramount, following standard industry practice, wouldn't be reporting that number publicly.
Any difference would presumably be immaterial to the success of the movie or Paramount's bottomline. "Transformers: Age of Extinction" is on track to gross more than $250 million domestically and significantly more overseas. Paramount said Monday that the movie has already grossed $202.1 million internationally, slightly more than it estimated on Sunday.
Typically, studios keep about half of domestic box office receipts and a bit less overseas. In China, where "Transformers" has already grossed $92 million, studios keep only 25%.