Question: red back spider how big?
Answer: Females have a body length of about 1 centimetre (0.39 in), while the male is smaller, being only 3–4 mm (0.12–0.16 in) long. The redback is one of few arachnids that usually display sexual cannibalism while mating. The adult female redback has a round body about 1 centimetre (0.4 in) long, with long, slender legs.