Zac Efron was 29 years old during The Greatest Showman, which was released in 2017. Key points:

• Zac Efron was born on October 18, 1987. This makes him 29 turning 30 in 2017, depending on the filming timeline and release date.

• The Greatest Showman premiered in December 2017, so Efron was 30 at the time of release if counting by December 2017, or 29 during most of the production period earlier that year.

• The film co-starred Hugh Jackman and Zendaya, with Efron playing Phillip Carlyle, a role introduced in the narrative alongside the ensemble.

If you’d like, I can verify exact filming dates vs release dates to pin down whether you want his age strictly on the date of release or on a specific filming milestone.