Now That's What I Call Music! 45 is the 45th edition of the Now! series in the United States. It was released on February 5, 2013, on CD and from major digital retailers. The album debuted at No. 3 on the Billboard 200 albums chart with first week sales of 87,000 units. The album has sold 441,000 copies in the US as of July 2013.
With the release of Now! 45, Andy Kellman of AllMusic claims "the series remains a timely and an accurate reflection of the Billboard Hot 100 chart." Six songs in the collection reached the top ten, while "all 16 of the principal songs were still on the Hot 100" at the time of the album's release. He also notes the continued dominance of dance-pop, although songs by Phillip Phillips, Imagine Dragons, and Florida Georgia Line do "break it up a bit."