16 contracts and counting.
The Celtics have been holding off on finalizing a couple of deals that have been agreed to in principle in order to maintain maximum flexibility. Jae Crowder will officially re-sign with the Celtics and the team will complete the David Lee trade soon, but waiting on those deals allowed the team to trade for Perry Jones III and could (in theory) still allow them to make yet another move where the team takes on more salary than it sends out.
However, the roster already stands at 16 guaranteed contracts (Babb is non-guaranteed and could be headed out in the Lee deal anyway) and barring any last minute changes, the roster moves could be over for the summer.