The small and large intestines are a vital part of the human digestive system. The length of the small intestine is roughly 9–16 feet (ft), while the large intestine is shorter, measuring about 5 ft long.
The intestines sit in the abdomen and absorb nutrients, vitamins, and water. They form part of the gastrointestinal (GI) tract and the latter section of the digestive system. Together, the intestines run from the end of the stomach to the anus.
While the intestines can fit inside the abdomen, they are much longer than many people may realize. The exact length of the intestines can also vary from person to person.
Older research investigating the length of the intestines in people who donated their body to science suggests an average total intestinal length of about 26 ft, with a range of 21.9 ft to 30.3 ft.
The study authors emphasize that measurements of intestinal length are rare. For this reason, there is no scientific evidence that intestinal size or length correlates with health or affects how well digestion works.
In this article, we discuss what the research says about the length of the small and large intestines.
The small intestine is actually longer than the large intestine but gets its name from its smaller diameter. It is located toward the bottom of the abdomen and connects the stomach to the large intestine.
The small intestine consists of three distinct parts:
- Duodenum: The duodenum is the first and shortest portion of the small intestine. It completes the first part of digestion by mixing enzymes from the stomach and pancreas to break down food further.
- Jejunum: The walls of the jejunum help absorb nutrients from food, using tiny hairs called villi. The walls also include circular folds called plicae circulares. These increase the total surface area of this portion of the small intestine, helping it effectively absorb nutrients.
- Ileum: The ileum helps absorb any remaining nutrients before food moves to the large intestine. It plays a key role in absorbing vitamin B12 and bile acids. It is also the longest section of the small intestine.
It is difficult to measure the length of the small intestine in a healthy living person, but researchers estimate that it ranges from about 9.8 ft to 16.4 ft.
The three sections of the small intestine differ significantly in length:
- The duodenum is about 7.9–9.8 inches (in).
- The jejunum is about about 8.2 ft long.
- The ileum is close to 9.8 ft long.
Older research found that the total length of the intestines correlates with weight, such that people who weigh more have longer intestines. Younger people and males also have, on average, longer intestines.
The small intestine is long enough that a person can undergo small bowel resection surgery to remove part of it if an underlying disease or condition causes it to stop functioning.
The large intestine, which doctors also call the colon, has a larger diameter than the small intestine. The primary function of the large intestine is to reabsorb fluids, electrolytes, and vitamins and then form and propel feces toward the rectum for elimination.
It contains four distinct parts:
- Cecum: Also known as the ileocecal junction, this section joins the intestines. The cecum helps absorb water and any remaining salts.
- Colon: The colon, the longest portion of the large intestine, is a segmented portion that absorbs more water and electrolytes.
- Rectum: The rectum stores feces after digestion.
- Anal canal: The anus is the final portion of the large intestine, and it helps a person have bowel movements.
As with the small intestine, the total length of the large intestine varies from person to person. Heavier people, younger people, and males generally have longer intestines. In most people, it is about 5 ft long.
The colon is the longest part of the large intestine, while the cecum measures about 2.4 in long. The rectum is about 7.5 in long, and the anus, the smallest part of the large intestine, is about 1 in long.
Some people with certain health conditions may need to undergo a colon resection, or colectomy, to remove part of or the whole large intestine.
People who find it difficult to visualize the length of the intestines may find these comparisons helpful:
- The large intestine, when stretched, is similar to the height of a short adult. The smallest portions of the large intestine are about the length of a thumb.
- The small intestine, on average, is longer than a van and about the length of a medium sized pickup truck. Small intestine lengths differ among individuals by about the height of a very tall person.
- Research suggests that the total surface area of the intestines is roughly half the size of a badminton court.
The length of the intestines can vary greatly among individuals. Research suggests that the combined length of the small and large intestines is at least 15 ft in length. The small intestine can measure about 9–16 ft, while the large intestine is roughly 5 ft long.
The intestines have the important role of helping break down and absorb nutrients from food and drink. Generally, the length of the intestines should not affect a person’s life.