It was the second-highest February debut ever, behind The Passion of the Christ's $83.9m opening in 2004.
Based on EL James' best-selling novel, Fifty Shades of Grey is directed by Sam Taylor-Johnson and stars Jamie Dornan and Dakota Johnson.
According to Universal Pictures, North American audiences were 68% female.
The film's takings were more than double those of its nearest box office rival, Kingsman: The Secret Service, which earned $35.6m (£24m), according to studio estimates.
Around the world, Fifty Shades of Grey took an estimated $158m (£102m) from 58 countries.
James's trilogy of Fifty Shades books have reportedly sold more than 100 million copies worldwide and been translated into more than 50 languages.
The film, which contains "strong sex and nudity", is R-rated in the US - meaning those under 17 years old can watch it if accompanied by an adult - and has an 18 certificate in the UK.
Animated children's film The SpongeBob Movie: Sponge Out of Water came third on the box office chart with $30.5m (£19.8m) in its second weekend on release.
Rounding out the top five were the Oscar-nominated American Sniper with $16.4m (£10.6m), and sci-fi fantasy Jupiter Ascending with $9.4m (£6.1m).
Erotic film adaptation Fifty Shades of Grey sizzled at North American box offices this weekend, taking an estimated $81.7m (£53m).