The reel watchtime indicates how long viewers watch a creator's reels on average.
A high watchtime relative to the reel length signals that the content holds attention — a key quality signal for the Instagram algorithm and an indicator of how well brand placements in reels are actually seen.
More precisely, Reel Watch Time is the total number of hours a single reel is watched by all viewers together, shown in the profile as hours per reel and compared with creators of a similar follower count. Calculation: Reel (finished views) x Reel (duration). Some reels are only a few seconds long while others run for a minute or more; the play counts do not show this difference, but the watch time does. For campaigns this tells you how much total on-screen time a sponsored reel actually gets.