The GHO is one of the largest North American owls, and while the turkey is still bigger, the owls are built to take down animals much larger than one would expect.

Some quick stats I grabbed from Google:

Adult great horned owls range in length from 43 to 64 cm (17 to 25 in), with an average of 55 cm (22 in), and possess a wingspan of 91 to 153 cm (3 ft 0 in to 5 ft 0 in), with an average of 122 cm (48 in). Females are somewhat larger than males.[15][22] Mean body weight is 1,608 g (3.545 lb) for females and 1,224 g (2.698 lb) for males.

Mature males [wild turkey] are about 2.5 feet tall and weigh up to 25 pounds. The average weight is 18 to 20 pounds. The females (hens) are smaller than toms and weigh 9 to 12 pounds. [4kg to 5.5kg]

Here’s a picture I feel accurately depicts their size. Lots have the owl closer to the camera to look bigger, but this is pretty realistic.

They also have tremendous grip strength of about 350 to 500 psi, where your typical large scary dog is about 250 psi.