The Barn Owl is a pale, long-winged, long-legged owl with a short squarish tail. Generally a medium-sized owl, there is considerable size variation across the subspecies. The Barn Owl measures about 25–50 cm (9.8–20 in) in overall length, with a wingspan of some 75–110 cm (30–43 in). Adult body mass is also variable, ranging from 187 to 800 g (6.6 to 28 oz), with the owls closer to the tropics being generally smaller.
Tail shape is a way of distinguishing the Barn Owl from true owls when seen in flight, as are the wavering motions and the open dangling feathered legs. The light face with its heart shape and the black eyes give the flying bird an odd and startling appearance, like a flat mask with over-sized oblique black eye-slits, the ridge of feathers above the bill somewhat resembling a nose.