Your intestines are roughly 25 feet (7.5 meters) long in total when measured in a living person. The small intestine accounts for about 20 feet of that, while the large intestine adds another 6 feet. These numbers vary quite a bit from person to person, and they also depend on how and when the measurement is taken.
Total Length of the Small Intestine
The small intestine is the longest organ in your digestive system, averaging about 600 cm (20 feet). It coils and folds extensively to fit inside your abdominal cavity, which is why it’s easy to underestimate just how much tubing is packed in there. The three segments break down like this:
- Duodenum: about 25 cm (10 inches), the shortest section, connecting directly to your stomach
- Jejunum: about 200 cm (6.5 feet), where most nutrient absorption happens
- Ileum: about 300 cm (10 feet), the longest segment, handling the remaining absorption before passing contents to the large intestine
These are averages. A study published in the American Journal of Roentgenology measured the small intestine in 31 patients both during surgery and on MRI scans, and found individual lengths ranged from 150 cm all the way to 749 cm. That’s a fivefold difference between the shortest and longest. The average in that group was about 414 cm (roughly 13.5 feet), measured from the end of the duodenum to the start of the large intestine.
Total Length of the Large Intestine
The large intestine (colon) averages about 190 cm, or just over 6 feet. It’s significantly wider than the small intestine, with an average diameter of 4.8 cm compared to the small intestine’s 2.5 cm. That wider diameter is part of why it’s called “large,” even though it’s much shorter. The large intestine’s main job isn’t absorbing nutrients. It reclaims water from digested food, houses the bulk of your gut bacteria, and forms stool.
Why Measurements Vary So Much
You’ll sometimes see the small intestine described as 20 feet long, other times as 15 feet, and occasionally even longer. Several factors explain the discrepancy.
The biggest one is whether the intestine is measured in a living person or after death. When you’re alive, your intestinal muscles maintain a baseline level of tension (called muscle tone) that keeps the organ somewhat contracted. After death, that tone disappears and the tissue relaxes and stretches. Cadaver measurements routinely come in longer than measurements taken during surgery or on imaging. Many of the classic textbook numbers came from cadaver studies, which is why older sources tend to report longer figures.
Modern MRI techniques closely match what surgeons find when they measure directly. In the study comparing MRI to surgical measurement, the average difference between the two methods was only about 20 cm, a discrepancy of less than 5%. For shorter intestines under 200 cm, the two methods differed by just 4.7 cm on average. That kind of accuracy matters for patients who’ve had portions of their intestine removed and need precise tracking of what’s left.
Height, age, and sex also play a role. Taller people generally have longer intestines, and there’s natural biological variation just like there is with arm span or leg length.
Surface Area Matters More Than Length
Length alone undersells what the small intestine actually accomplishes. If you could flatten the inner lining of the small intestine, accounting for all its folds, finger-like projections called villi, and the even tinier microvilli covering those projections, the total surface area reaches about 30 square meters. That’s roughly the size of a studio apartment. The villi alone multiply the intestinal surface area by about 6.5 times, and the microvilli multiply it by another 13 times on top of that.
The large intestine, by contrast, has a much smoother inner lining. Its total surface area is only about 1.9 square meters, roughly the size of a twin mattress. It doesn’t need the same absorptive capacity because most nutrients have already been captured upstream.
How Intestines Grow From Birth
A newborn’s small intestine is about 250 cm (just over 8 feet) long. By adulthood, it roughly triples in length to about 750 cm. Most of this growth happens during childhood and adolescence alongside overall body growth. The large intestine follows a similar pattern, starting much shorter and reaching its full adult length during the teenage years.
How Much Intestine You Actually Need
People can survive with significantly less intestine than they were born with. When disease or injury requires surgical removal of large sections, the remaining intestine can often adapt by increasing its absorptive capacity over time. This condition, called short bowel syndrome, becomes a concern when the small intestine is reduced to roughly 200 cm or less.
Data from neonatal patients at JAMA Surgery shows just how adaptable the gut can be. Among infants with short bowel syndrome, those who were eventually able to eat and absorb nutrition normally had a median remaining small intestine of 55 cm, about 22 inches. Even more remarkably, 28% of infants with 30 cm or less of small intestine were eventually weaned off intravenous nutrition entirely. The shortest functional small intestine in that group was just 12 cm, under 5 inches, though cases like that are the exception and depend heavily on whether the valve between the small and large intestine is still intact.