An adult human body has 206 bones. The SEER training modules of the US National Cancer Institute put 80 of them in the axial skeleton: the skull, the spine and the rib cage. The other 126 form the appendicular skeleton, the limbs and the girdles that join them to the trunk. SEER adds one careful word: the adult skeleton "usually" has 206 named bones.
A newborn has more, about 270 to 300 depending on the reference, because many bones begin as separate pieces that fuse during growth. Many adults also carry a few small bones that the standard count leaves out.
How the 206 bones are counted
The count follows a fixed list of named bones. SEER prints the list bone by bone, and the table groups the same numbers by region.
| Region | Bones | Count |
|---|---|---|
| Skull | 8 cranial and 14 facial bones | 22 |
| Ear ossicles | Malleus, incus and stapes in each ear | 6 |
| Hyoid | One U-shaped bone in the neck | 1 |
| Vertebral column | 7 cervical, 12 thoracic and 5 lumbar vertebrae, sacrum, coccyx | 26 |
| Ribs and sternum | 24 ribs and the sternum | 25 |
| Axial skeleton, total | Skull, ossicles, hyoid, spine and rib cage | 80 |
| Shoulder girdles | 2 clavicles and 2 scapulae | 4 |
| Upper limbs | In each: humerus, radius, ulna, 8 carpals, 5 metacarpals, 14 phalanges | 60 |
| Pelvic girdle | 2 hip bones | 2 |
| Lower limbs | In each: femur, patella, tibia, fibula, 7 tarsals, 5 metatarsals, 14 phalanges | 60 |
| Appendicular skeleton, total | Girdles and limbs | 126 |
| Whole skeleton | Axial plus appendicular | 206 |
Skull counts differ between references. Gray's Anatomy (1918) counts 22 skull bones: eight in the cranium and fourteen in the face. SEER files the six ear ossicles under the skull and prints 28. The hyoid is a separate bone and has its own line.
Each hand has 27 bones and each foot has 26, so the hands and feet together hold 106 bones. Every bone in the table is named on the 3D skeleton.
Why a newborn has more bones than an adult
SEER and Gray's Anatomy give no total for a newborn, but both describe bones that form from separate centers and join later. Two other references give a number, and they differ. StatPearls, the clinical reference carried on the US National Library of Medicine's Bookshelf, says human infants typically have 270 bones. A 2021 review of bone development in the journal Developmental Dynamics says humans have approximately 300 bones at birth.
Both figures are approximations, and the gap comes from what is counted as one bone. A newborn skeleton is made of bony pieces joined by cartilage. Gray's Anatomy and SEER describe how those pieces merge:
- The lower jaw is two segments at birth that join at the chin during the first year, says Gray's. The frontal bone of the forehead also starts as two halves, and its suture is usually closed by the eighth year, except at its lower part.
- Each hip bone forms from three bones, the ilium, ischium and pubis, which are separate at birth. The last parts join the rest of the bone between the twentieth and twenty-fifth years, per Gray's.
- A long bone has a shaft and separate ends, with a plate of growing cartilage between them. In the femur, Gray's puts a new bony center in the head at the end of the first year, in the greater trochanter in the fourth year and in the lesser trochanter at 13 to 14. The lower end joins the shaft at about age 20, and SEER says growth in length usually stops in the early twenties.
The spine shows the arithmetic. It develops as 33 vertebrae. Gray's says five of them fuse into the sacrum, a process that starts at about age 18 and is complete between 25 and 30, and four small ones form the coccyx. That leaves 24 separate vertebrae and 2 fused bones: the 26 in the table.
Count each separate piece and the newborn total is higher. Count pieces that will become one bone as one and it is lower. Neither source lists the pieces it counted, so 270 and about 300 are best read as rounded estimates of the same skeleton.
Why some adults do not have exactly 206
The 206 are the bones on the standard named list. Three kinds of extra bone sit outside it.
Sesamoid bones are small, round bones that form inside tendons. Gray's Anatomy says two sesamoids are constant at the base joint of the thumb and two are always present under the joint of the big toe, while others turn up only now and then. The kneecap is the largest. Some others are common too. A pooled analysis of 19 studies in Clinical Anatomy found sesamoids at the base joint of the thumb in 99.9 percent of adults. A 2020 analysis in the Journal of Anatomy found a fabella, a sesamoid behind the knee, in 36.8 percent of knees worldwide.
Extra ribs are rarer. The rib cage has 12 pairs. A cervical rib is an extra rib in the neck. A study of 1,352 chest X-rays in London found one in 0.74 percent of people: 1.09 percent of women and 0.42 percent of men. A 2024 pooled analysis of nine studies put lumbar ribs, extra ribs in the lower back, at 2.1 percent.
Sutural bones, also called Wormian bones, are small irregular bones that form along the sutures, the joints between skull bones. Three studies of dry adult skulls show how common they are. They turned up in 35.3 percent of 147 skulls from north India, 63.9 percent of 285 Chinese skulls and 74.7 percent of 166 Greek skulls.
The longest, smallest and strongest bones
| Record | Bone | Figure | Reference |
|---|---|---|---|
| Longest | Femur (thigh bone) | Longest bone in the skeleton | Gray's Anatomy |
| Strongest | Femur | Called the strongest bone in the skeleton | Gray's Anatomy |
| Second longest | Tibia (shin bone) | Longest bone after the femur | Gray's Anatomy |
| Smallest | Stapes (middle ear) | Mean height 3.43 mm | Genome Research; Ear, Nose and Throat Journal |
| Largest sesamoid | Patella (kneecap) | Sits in the tendon of the front thigh muscle | Gray's Anatomy |
Gray's Anatomy names the femur as both the longest and the strongest bone in the skeleton, and the tibia as the longest after it.
The smallest bone is the stapes, one of the three ossicles of the middle ear. A 2026 paper in Genome Research calls it the smallest bone in the human skeleton. Micro-CT scans of the stapes in ten skulls gave a mean height of 3.43 mm, with a range of 3.20 to 3.80 mm. A CT study of 60 ears gave 3.48 mm.
How much of body weight is bone
References differ because they weigh different things. The International Commission on Radiological Protection (ICRP) sets the skeleton of its reference man at 10.5 kg out of 73 kg, about 14 percent. For its reference woman the figure is 7.8 kg out of 60 kg, about 13 percent. Those masses include the bone marrow.
SEER gives about 20 percent, but for the whole skeletal system, which it defines as bones together with cartilage, ligaments and tendons. It is one of the organ systems of the human body.
Skeletal muscle is much heavier: 29 kg in the same reference man and 17.5 kg in the reference woman, about 40 and 29 percent. So a share of 30 to 40 percent describes muscle, and bone is closer to 14.