What is the Biggest Bone in the Human Body?

right and left femur bones - the largest, strongest, and heaviest bones in the human body

Did you know that the biggest bone in the human body is hiding right inside your thigh? It’s called the femur, and it’s not just the longest bone you have. It’s also the heaviest and the strongest.

What is the biggest bone in the human body?

The femur, also known as the thigh bone, is the biggest bone in the human body. Every time you stand up, walk, run, or jump, your femurs are hard at work. Without them, your legs wouldn’t work.

Where is the largest bone in the human body?

Your femur runs down the length of your upper leg, all the way from your hip to your knee. You have one in each leg.

femur - thigh bone - biggest bone in human body

At the top, the femur connects to your pelvis to form your hip joint. At the bottom, it connects to your shinbone and kneecap to form your knee.

The ends of the femur are cushioned by cartilage, a smooth, slippery material that keeps your joints from grinding together every time you move.

If you press your fingers into the front of your thigh, you can feel the firm shape of the femur underneath.

How big is the biggest bone in the human body?

The femur grows as you grow, so its size depends on how tall you are. In most people, your femur is about one-quarter of your total height. So, the taller you are, the longer your femur.

If you’re 4 feet tall, your femur is roughly 1 foot long. If you’re closer to 5 feet, it’s about 15 inches, which is longer than most school rulers.

You can actually use the femur to guess a person’s height. This is something forensic scientists and archaeologists do when they find skeletons — pretty useful if all you have left is a single bone.

What’s inside the femur bone?

Like all long bones, the femur has a hard outer shell and a softer inside. That inside is filled with bone marrow, the spongy material where your body makes blood cells every single day.

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Human Body Learning has strict sourcing guidelines and relies on information from peer-reviewed research studies, academic institutions, and medical associations.

Published on March 14, 2025. Updated on June 23, 2026 by Betty Choi, MD

Published on March 14, 2025. Updated on June 23, 2026 by Betty Choi, MD

Dr. Betty Choi pediatrician

Betty Choi, MD

Dr. Betty Choi is a Harvard-trained pediatrician who makes learning fun and doable. She created the kids’ anatomy book Human Body Learning Lab, which Science Magazine recommends as a “notable standout in the genre.”