Description. An average adult American alligator's weight and length is 360 kg (790 lb) and 4.0 m (13.1 ft), but they sometimes grow to 4.4 m (14 ft) long and weigh over 450 kg (990 lb). The largest ever recorded, found in Louisiana, measured 5.84 m (19.2 ft). The Chinese alligator is smaller, rarely exceeding 2.1 m (6.9 ft) in length. In addition, it weighs considerably less, with males rarely over 45 kg. No average lifespan for an alligator has been measured.