Margot Robbie and Will Smith’s con-man caper Focus has taken out the top spot at the US box office.

According to studio estimates on Sunday, Warner Bros’ Focus easily topped all competitors on a weekend with little competition at North American multiplexes.

The R-rated Focus overwhelmingly appealed to adults, with 88 per cent of its audience older than 25.

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In second place was the Colin Firth spy thriller Kingsman: The Secret Service, which made $US11.8 million ($A15.1 million) in its third week of release.

After two weeks atop the box office, Fifty Shades of Grey continued its steep slide, landing in fourth with an estimated $US10.9 million for Universal Pictures.

The top films at the US Box Office

1. Focus

2. Kingsman: The Secret Service

3. The SpongeBob Movie: Sponge Out of Water

4. Fifty Shades of Grey

5. The Lazarus Effect

6. McFarland, USA

7. American Sniper

8. The DUFF

9. Still Alice

10. Hot Tub Time Machine 2