Additional earnings from television sales, DVDs and downloads are likely to generate a further US$20 million at least for Bullock.
Bullock, tipped to win Best Actress at the Oscars, will close the pay gap between Hollywood's biggest male and female stars. Last year Forbes named Robert Downey jnr the highest paid actor with earnings of US$75 million, of which US$50 million came from his role as Iron Man.
Bullock's windfall is partly down to timing, luck and smart negotiating skills. The actress was riding high after her Oscar win for The Blind Side when the deal was struck in 2010.
Angelina Jolie had pulled out of Gravity when her management failed to strike a deal with Warner Bros. The studio needed an A-list replacement who could carry the film's long sequences of a woman floating alone in space, giving Bullock considerable leverage.
Such "first dollar" guaranteed box office deals for actors are becoming rare, the Hollywood Reporter said, because studios now want to recoup all the costs for expensive productions before sharing the profits with talent.
Bullock's co-star George Clooney, Gravity director Alfonso Cuaron and producer David Heyman are also believed to have "back end" pay deals.
Cuaron and Heyman may have renegotiated their deals during shooting, reducing their upfront fees, in order to keep the ambitious 3D film on track as the budget rose beyond US$110 million. Bullock's windfall contrasts with the admission by fellow Oscar-nominee Jonah Hill that he gladly accepted the Screen Actors Guild minimum of US$60,000 to work with Martin Scorsese and Leonardo DiCaprio on The Wolf of Wall Street. "I would sell my house and give [Scorsese] all my money to work for him," Hill said.
Downey jnr was denied his own Gravity payday. He was originally cast as the lead but Avengers and Iron Man 3 scheduling conflicts ended his involvement.
If Bullock gets to deliver another Oscar-winning speech, she might be advised to thank the team which boosted her bank balance - her representatives at CAA and the Ziffren Brittenham law firm.
Bullock has selected her roles sparingly in recent years. She is next due to appear as the voice of villain Scarlet Overkill in Minions, a 3D animated prequel to Despicable Me. Gravity is up for 10 prizes at the Oscars including best film and best director for Cuaron.