How large do tapeworms get? August 3, 2020 by Pamela Landy Tapeworms range in size from about 0.04 inch to more than 50 feet in length. Related Answers In what American cities were the following world’s fairs held? How many dogs and cats are there in the United States? How large a tree can a beaver cut down? How large was the city of Troy? How large is the Silicon Valley? What percentage of Southern families owned large plantations in the U.S.?