The small intestine is about 22 feet (6.7 meters) long, and the large intestine is about 6 feet (1.8 meters) long. Combined, that’s roughly 28 feet of intestine coiled inside your abdomen. The naming can be confusing: the “small” intestine is actually far longer. The names refer to diameter, not length. The large intestine is wider, averaging about 3 inches across, while the small intestine is narrower.
Why Measurements Vary So Much
If you’ve seen wildly different numbers for intestinal length, there’s a good reason. For decades, scientists measured intestines during autopsies, when the muscle tissue has fully relaxed and stretched out. In a living person, the smooth muscle lining the intestinal wall holds everything in a more contracted state. Imaging studies on living subjects put the small intestine closer to 10 to 16 feet, significantly shorter than the 22-foot figure often cited from post-mortem measurements.
Both numbers appear in medical literature, which is why you’ll see different answers depending on the source. The 22-foot figure remains the most commonly referenced in anatomy textbooks, but the real functional length in your body right now is likely shorter.
Small Intestine: Three Distinct Sections
The small intestine is divided into three parts, each with a different role in digestion and absorption.
- Duodenum: The first and shortest section, about 25 cm (10 inches) long. It connects directly to the stomach and is where digestive enzymes from the pancreas and bile from the liver mix with food.
- Jejunum: The middle section, roughly 200 cm (about 6.5 feet) long. This is where most nutrient absorption happens.
- Ileum: The longest section at about 300 cm (nearly 10 feet). It absorbs remaining nutrients, especially vitamin B12 and bile salts, before passing contents into the large intestine through a one-way valve called the ileocecal valve.
What makes the small intestine remarkable isn’t just its length. The inner lining is covered in tiny finger-like projections called villi, and those villi are covered in even smaller projections called microvilli. These folds increase the absorptive surface area dramatically. Villi expand the surface by about 6.5 times, and microvilli multiply it another 13 times on top of that. The result is an internal surface area of roughly 30 square meters, about the size of a small studio apartment, all packed inside a tube you could hold in your hands.
Large Intestine: Four Main Segments
The large intestine forms an upside-down U shape that frames the small intestine in your abdomen. Its segments are named for the direction they travel.
- Ascending colon: Runs upward along the right side of your abdomen, about 20 to 25 cm (8 inches) long.
- Transverse colon: Crosses horizontally beneath your stomach, the longest segment at roughly 40 to 50 cm (over 18 inches).
- Descending colon: Travels downward along the left side, about 25 cm (10 to 12 inches).
- Sigmoid colon: An S-shaped curve that connects to the rectum, averaging 40 to 45 cm (about 18 inches) but varying widely between individuals, from as short as 12 cm to as long as 84 cm.
After the sigmoid colon, the rectum adds another 10 to 15 cm (5 to 6 inches), and the anal canal accounts for the final few centimeters. The large intestine’s primary job isn’t absorbing nutrients. Instead, it reclaims water and electrolytes from the remaining material, compacts waste, and houses the vast majority of your gut bacteria.
How Much Intestine You Actually Need
The body has significant reserve capacity when it comes to intestinal length. People can lose portions of their intestine to surgery and still absorb enough nutrition to survive without intravenous feeding. The threshold depends on which parts remain. A person typically needs a minimum of 60 to 90 cm of small intestine if they still have part of their colon, or about 150 cm of small intestine if the colon has been removed entirely.
Below those thresholds, a condition called short bowel syndrome develops, where the remaining intestine can’t absorb enough water and nutrients to sustain the body. This is relatively rare and usually results from surgical removal of damaged or diseased sections, not from natural variation in intestinal length.
Individual Variation
Intestinal length varies considerably from person to person. Height, sex, and body composition all play a role, and the sigmoid colon alone can differ by a factor of seven between individuals. There’s no single “correct” number for how long your intestines are, which is part of why published measurements span such a wide range. The figures above represent averages across large populations, and your own intestines could be meaningfully shorter or longer without any impact on your health.