how many miles of blood vessels in the human  body
When the blood vessels are this small they are called capillaries. There are more capillaries (and more miles of capillaries) than any other kind of blood vessel. To answer your question, there are approximately 60,000 miles of blood vessels in an adult human body. That's about 100,000 kilometers. And if you really did stretch out your vessels for 60,000 miles most of them would be capillary miles. Each capillary is very short, but there are so very many of them. I found the answer to your question in a college textbook of human anatomy and physiology.