"An average inch of hair weighs about 50 µg - a light estimate, as blonde hair tends to be lighter than other colors. Animators have said that Rapunzel's hair is approximately 70 feet (840 inches), and consists of about 100,000 strands. That yields 4,200,000,000 µg = 4,200,000 mg = 4,200 g = 4.2 kg (approx 10.4 lbs) of hair. We assume that its manageable weight in the movie is another innate magical property."