 Lightcurve analysis gave a rotation period of 2.900 and 3.087 hours with a brightness amplitude of 0.22 and 0.20 magnitude, respectively ().According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, "Gefion" measures between 6.965 and 7.016 kilometers in diameter and its surface has an albedo between 0.2489 and 0.252.The "Collaborative Asteroid Lightcurve Link" assumes a standard albedo for carbonaceous asteroids of 0.057 and consequently calculates a much larger diameter of 12.62 kilometers based on an absolute magnitude of 13.22.