For “Harry Potter” and Hollywood, eight is the magic number.

Warner Bros. Pictures and the producers behind the $4.5-billion film franchise featuring the beloved boy wizard will split the seventh and final novel in the J.K. Rowling series into two films.

“Harry Potter and the Deathly Hallows: Part I” will hit theaters in November 2010, followed by “Part II” in May 2011, a decision that is being met around the world with fans’ cheers but also plenty of cynical smirks. The publishing industry is learning to live without new “Potter” releases, but Hollywood just pulled off a trick that will keep its profitable hero on his broom into the next decade.

Any twist in the “Potter” universe is the stuff of global news bulletins. The books were a publishing sensation. And to an entire generation, the film saga has become a heartfelt touchstone on the level of “The Wizard of Oz” and as culturally and commercially ubiquitous as the “Star Wars” series. For all those reasons, everyone involved in the franchise is jumping forward to say an eighth film would be to serve the story, not the bottom line.

Daniel Radcliffe, the star of the franchise, said it was the dense action of the final novel that made the decision, not any executive or ledger.

“I think it’s the only way you can do it, without cutting out a huge portion of the book,” Radcliffe said. “There have been compartmentalized subplots in the other books that have made them easier to cut -- although those cuts were still to the horror of some fans -- but the seventh book doesn’t really have any subplots. It’s one driving, pounding story from the word go.”

The same could be said about the relentless “Potter” franchise, which hit screens for the first time in 2001. The five “Potter” films to date have averaged $282 million in U.S. grosses, but the overall receipts go well beyond that. The faces of the stars stare out from DVDs, video games, tie-in books, toys, clothing, candy wrappers and a staggering array of other items. By some estimates, the brand represents a $20-billion enterprise, and that’s without the planned “Potter"-themed complex opening next year at the Universal Orlando Resort in Florida.

Extending the “Potter” franchise is a boon to the studio and to its parent, media giant Time Warner, where recently named Chief Executive Jeffrey Bewkes is reining in costs with moves such as the recent gutting of New Line Cinema. Time Warner’s stock price has stagnated since its merger with America Online eight years ago.

Right now, Radcliffe and his costars are filming the sixth installment in the franchise, “Harry Potter and the Half-Blood Prince,” at an old aircraft factory outside London. “It’s been brilliant,” Radcliffe said of the production. “It’s also, I think, the funniest of the films so far.”

Radcliffe is now 18 and, by the final film, will have spent half of his life in the role of the scarred orphan who finds friendship and danger within the stone corridors of Hogwarts School of Witchcraft and Wizardry. Each film (following the construct of the novels) has been framed by a school year. Producer David Heyman, a key figure in the films from Day One, was reluctant to depart from that and make the last book into two movies.

“Unlike every other book, you cannot remove elements of this book,” Heyman said. “You can remove scenes of Ron playing Quidditch from the fifth book, and you can remove Hermione and S.P.E.W. [Society for the Promotion of Elfish Welfare] and those subplots . . . but with the seventh, that can’t be done.”

Rowling, who signed off on the idea of a two-part finale, has been a more frequent visitor to the sixth movie’s set than with previous installments. One big reason is that she is no longer busy trying to finish the “next” “Potter” book; she walked away from her signature character in July, when the climactic “Deathly Hallows” hit stores and sold a record 11 million copies in its first 24 hours on shelves.

Alan Horn, president and chief operating officer of Warner Bros. Entertainment, will be in Las Vegas today to talk up the “Potter” plans at ShoWest, a key annual conference of movie exhibitors. Horn said Wednesday that “it would have been a disservice” to downsize “Deathly Hallows” into one film.

“This way, we have an extra hour and a half, at least, to celebrate what this franchise has been and do justice to all the words and ideas that Jo has put in the amazing story,” Horn said. “This is the end of the story too. We want to celebrate it. We want to give a full meal.”

David Yates, director of the fifth and sixth films, will return and make the final two films concurrently. Screenwriter Steve Kloves also returns, and, by the completion of the franchise, he will have written seven of the eight films.

They will be adapting a seventh book with 759 pages packed with action and twists and turns in the race toward the final conflict between Potter and the dark lord who murdered his parents, the serpentine Lord Voldemort. Reviewing last summer for The Times, Mary McNamara wrote: “What Rowling has achieved in this book and the series can be described only as astonishing. Just as her characters have matured, the language and tone of the books have grown in sophistication and lyricism. But she has never lost the sense of wonder that has propelled her into literary legend.”

After the dust settles, the book ends with an epilogue that finds the main characters -- Harry, Hermione Granger and Ron Weasley -- grown up, married and 19 years removed from Hogwarts. Horn said that particular denouement has the filmmakers fretting about how to keep the young familiar stars on the screen just before it goes dark.

“That,” Horn said, “is something we will need to deal with. People have watched these kids grow up, and it’s been very special to do so. That’s important to us.”

Heyman said splitting “Deathly Hallows” is the right narrative formula, but the next problem is figuring out the division. As he put it: “The question will be, where do you break it? And how do you make them one but two separate and distinct stories? Do you break it with a moment of suspense or one of resolution?”

Horn said that screenwriter Kloves has already latched on to an approach that might work. Rowling could not be reached for comment, but the most recent entry on her website journal declared that “Hallows” stands as her favorite among the novels -- and that saying goodbye to Harry is never easy.

“It was the ending I had planned for 17 years, and there was more satisfaction than you can probably imagine in finally sharing it with my readers,” Rowling wrote. “As for mourning Harry -- and I doubt I will be believed when I say this -- nobody can have felt the end as deeply as I did.”

geoff.boucher@latimes.com