How Do You Know opened at $7.6 million in the United States and Canada, making it eighth in the box office at its first weekend."Weekend Box Office Results for December 17-19". Box Office Mojo. Retrieved 2010-12-26. The film fell off the chart by its third weekend. On its opening day, December 17, 2010, it debuted at No. 5 behind Tron: Legacy, Yogi Bear, The Fighter and The Chronicles of Narnia: The Voyage of the Dawn Treader. By December 22, it was No. 11 in the box office. How Do You Know grossed a total of $48.7 million worldwide. In 2014, the Los Angeles Times listed the film as one of the biggest box office flops of all time.
