According to the survey carried out by NASA's Wide-field Infrared Survey Explorer with its subsequent NEOWISE mission, Watts measures 6.63 kilometers in diameter and its surface has an albedo between 0.276 and 0.294. The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.24 – derived from 8 Flora, the largest member and namesake of this asteroid family – and calculates a diameter of 7.14 kilometers with an absolute magnitude of 12.9.
