Pel's fishing owl is one of the largest owl species in the world. Among the world's owls, it ranks as the fifth heaviest on average, the seventh longest in length and measured wing chord and fourth longest in mean wingspan, although not all large species have had measured wingspans. It measures in length, spans around across the wings and weighs up to at least . One male was found to weigh and four females averaged , it may outrival the snowy owl (only around 4% lighter on average in six datasets) as the fifth or sixth heaviest living owl on average. Under current classification, it is the heaviest extant owl outside of the genus "Bubo", although some authors may also include the fishing owls in "Bubo". Among standard measurements, the wing chord is and the tail is long. They are well adapted to their aquatic lifestyle. Unlike most owls, they have minimal feathering on the toes and the tarsus, thus minimizing the amount of plumage that gets wet while fishing. Like diurnal raptors that specialize in fish, they have spiky scales on the bottoms of their feet that help them grip slippery fish. Since hearing and auditory stealth is not important to its hunting techniques, this owl does not have strong hearing and does not have the soft edges to its flight feathers that most owls share, which makes them almost impossible to hear in flight.