Stool, also called feces or a bowel movement, is the solid waste your body produces after digesting food. It’s made up of everything your digestive system couldn’t absorb or no longer needs: water, bacteria, undigested plant matter, fats, and dead cells shed from the lining of your intestines. While most people don’t think much about it, stool is one of the most accessible windows into your digestive health. Its shape, color, frequency, and consistency all carry useful information about how well your gut is working.
What Stool Is Actually Made Of
Roughly three-quarters of stool is water. The remaining quarter, the dry portion, is more interesting than most people expect. About 55% of that dry mass is bacteria, both living and dead, from the trillions of microbes that populate your large intestine. These bacteria play essential roles in breaking down food, producing vitamins, and maintaining immune function. When they’ve completed their lifecycle or get flushed along with digested material, they exit as a major component of your stool.
The rest of the dry weight includes about 25% undigested plant matter (fiber your body can’t break down), along with 2 to 15% fat, plus proteins, dead intestinal cells, and various digestive secretions like bile. Bile, produced by your liver, is what gives stool its characteristic brown color. As bile travels through your intestines, bacteria break it down into pigments that shift from green to yellow-brown to dark brown.
What Normal Looks Like
Normal bowel movement frequency ranges from three times a day to three times a week. A large population study of healthy adults without digestive conditions found that 98% fell within this range. Going once a day is common, but going every other day is equally normal as long as you’re comfortable.
Shape and consistency matter more than frequency when it comes to gauging digestive health. The Bristol Stool Scale, a clinical tool used by gastroenterologists, classifies stool into seven types based on form. Types 1 and 2 are hard, lumpy stools that suggest slow transit through the intestines and possible constipation. Types 3 through 5, ranging from a smooth sausage shape to soft blobs, are considered normal. Types 6 and 7 are mushy or entirely liquid, indicating the stool moved through too quickly for your colon to absorb enough water.
Stool form turns out to be a more reliable indicator of how fast food is moving through your gut than how often you go. Someone having daily bowel movements that consistently look like type 1 (hard, separate lumps) may have slower transit than someone who goes every two days but passes a smooth, soft stool.
What Stool Color Tells You
Medium to dark brown is the standard color for healthy stool, but temporary shifts are common and usually harmless. Green stool often means food moved through your large intestine faster than usual, so bile didn’t have time to fully break down. Eating large amounts of leafy greens or foods with green dye can produce the same effect.
Some color changes deserve attention. Black stool can signal bleeding in the upper digestive tract, such as the stomach or esophagus. Bright red stool often points to bleeding lower down, in the large intestine or rectum, frequently from hemorrhoids. Light, clay-colored, or white stool suggests a lack of bile reaching your intestines, which can indicate a blockage in the bile duct. If your stool is bright red or black, that warrants prompt medical attention.
Floating vs. Sinking
Most stool sinks, but floating is common and usually harmless. The most frequent cause is simply gas trapped inside the stool, which makes it less dense. High-fiber foods increase gas production during digestion, so a fiber-rich meal can easily produce a floater. Difficulty digesting lactose (the sugar in dairy) can do the same thing. In these cases, the stool looks normal aside from its buoyancy, and the floating resolves on its own.
Floating stool that looks greasy, oily, or unusually pale is a different situation. This appearance suggests your body isn’t absorbing fat properly, a condition called steatorrhea. You might notice oil floating in the toilet water or stool that sticks to the bowl and is difficult to flush. Fat malabsorption happens when your liver, pancreas, or bile ducts aren’t functioning correctly. Your liver produces bile and your pancreas produces enzymes that work together to break down dietary fat. If either organ is impaired, or if gallstones block the flow, excess fat passes through into your stool.
Why Stool Smells
The odor of stool comes from volatile organic compounds produced by bacterial fermentation in your colon. As gut bacteria break down proteins and other nutrients, they generate a complex mixture of organic acids, alcohols, and compounds like indole and skatole, both byproducts of protein digestion. Sulfur-containing foods like eggs, cruciferous vegetables, and garlic tend to produce more pungent odor because they fuel the production of sulfur-based gases.
A sudden, dramatic change in stool odor, especially if it becomes unusually foul and persists, can reflect a shift in gut bacteria or a problem with nutrient absorption. Infections, inflammatory conditions, and fat malabsorption all alter the chemical profile of stool in ways that produce distinctly stronger smells.
Mucus and Other Changes Worth Noting
A small amount of mucus in stool is normal. Your intestines produce mucus as a lubricant to help stool pass smoothly. But a noticeable increase in mucus, especially if it happens regularly or appears alongside blood, diarrhea, or abdominal pain, can point to intestinal infections, Crohn’s disease, ulcerative colitis, or other inflammatory conditions. Bloody mucus in particular signals something that needs evaluation rather than watchful waiting.
Pencil-thin stools that persist over several weeks, stool that consistently contains undigested food (beyond obvious items like corn kernels or seeds, which are normal), and a sustained change in bowel habits that lasts more than a few weeks are all patterns worth bringing up with a healthcare provider. Isolated oddities after a rich meal or a stomach bug are rarely concerning. It’s the persistent changes that carry diagnostic value.