A typical adult human has 12 pairs of ribs.
That makes 24 ribs in total, arranged on either side of the chest. Each rib attaches at the back to one of the 12 thoracic vertebrae. Together with the sternum, costal cartilages, and thoracic vertebrae, the ribs form the thoracic cage, which helps protect the heart and lungs and supports breathing movements.
The first seven pairs are called true ribs because each connects directly to the sternum through its own costal cartilage. Ribs 8 through 10 are false ribs because their cartilage joins the cartilage above rather than reaching the sternum independently. The 11th and 12th pairs are floating ribs; they attach to the spine but have no front attachment to the sternum.
A common quiz mistake is answering 24, which counts individual ribs rather than pairs. Most people have the standard 12 pairs, although anatomical variations occur. An extra cervical rib, arising near the neck, is an uncommon example and may sometimes cause symptoms.