Fifty Shades of Grey is on course for a box office haul of at least $500m worldwide after final totals for the film’s opening weekend showed that Sam Taylor-Johnson’s erotic romance scored the highest February opening of all time in north America.

Initial estimates from studio Universal suggested the adaptation of EL James’s bestselling literary knee-trembler had made $81.7m over its first three days in the US and Canada. But according to Variety that figure has now been upgraded to $85m. The new total places it ahead of the previous February best, the $83.8m bow made by Mel Gibson’s The Passion of the Christ in 2004.

Fifty Shades of Grey so dominates global box office it could whip Mamma Mia! Read more

The final figure for the longer four-day Presidents’ Day weekend in the US was also up on previously reported estimates, from $90.7m to $93m, though the studio itself had estimated a $94.4m return.

Worldwide, Fifty Shades opened to $266.6m over its first four days in cinemas, some way ahead of previously reported estimates of $248.7m. That total places the movie 18th on the list of the biggest global bows of all time.

“This kind of performance is usually reserved for superhero movies and animation franchises,” BoxOffice.com’s Phil Contrino told Variety, predicting an eventual return of more than half a billion dollars. “[Fifty Shades of Grey] joins that club.”

A $500m box office take would be an unprecedented haul for an erotic movie, unless one counts the reputed $600m worldwide taken by Deep Throat in 1972, when mechanisms did not exist to track the returns of a film that largely played in adult theatres. That figure is equivalent to $3.4bn in 2014 dollars, which would make the controversial porn movie the highest-grossing film of all time when adjusted for inflation.

In other Fifty Shades of Grey news, San Francisco television station KBCW reports that a drive-in cinema in nearby Concord is showing the erotic movie next to a screening of children’s adventure The SpongeBob Movie: Sponge Out of Water. Taylor-Johnson’s film, which features a number scenes of BDSM but avoids showing star Jamie Dornan’s penis, is reportedly visible from a shared parking lot.

“That’s not a good thing. What do the two have in common? And you can see both theatres,” local resident Joy Peter told the station.