how wide is the small intestine

The small intestine in adults typically has a diameter (width) of about 2.5 to 3 centimeters (approximately 1 inch), roughly the width of an index finger. In newborns, it is smaller, about 1.5 centimeters in diameter. The small intestine's width can be considered abnormally dilated when it exceeds 2.5 to 3 centimeters, depending on the imaging method used. This narrow diameter contrasts with its great length, which ranges from about 3 to 5 meters (10 to 16.5 feet) in a living adult, making it the longest part of the digestive tract despite being called "small" mainly due to its diameter. The inner surface area is highly increased by folds, villi, and microvilli, enhancing nutrient absorption.