The Bristol Stool Chart

The Bristol stool chart sorts poop into seven types by shape and texture, from Type 1 (separate hard lumps) to Type 7 (entirely liquid). Types 1 and 2 usually mean stool moved slowly and dried out on the way. Types 3 and 4 are the range clinical sources describe as typical. Types 5 to 7 mean it moved faster and kept more of its water. It is the standard way to describe stool, in clinics and in research.

The quick way to find your type: Stoolio estimates your Bristol type from one photo, along with a Stoolio Score and 12 visual readings, and keeps the record so your pattern shows up over time. Your first three scans are free.

What is the Bristol stool chart?

The chart was created in 1997 by Dr. Stephen Lewis and Dr. Ken Heaton at the Bristol Royal Infirmary in England, which is where the name comes from. Their study of 66 volunteers found that the shape of stool tracked how long food took to pass through the gut better than how often people went did. That made the chart useful: a simple picture-matching exercise stood in for a transit test that normally needs a lab.

Today the seven types are the shared vocabulary of digestive health. The Rome IV criteria, which gastroenterologists use to classify conditions such as irritable bowel syndrome, are written in Bristol types, and so are countless stool diaries and research studies. The descriptions below are the chart's own wording.

How to read the chart

Think of the scale as a dial for speed and water. The colon's job is to absorb water from what passes through it, so the longer stool stays, the drier and harder it gets. That gives the chart three zones:

• Types 1 and 2, the slow side. Hard, dry, sometimes difficult to pass. Cleveland Clinic says these types suggest constipation, and the Rome Foundation's own card labels them constipated stool.
• Types 3 and 4, the typical range. Formed, soft enough, easy to pass. Clinical reviews describe these two types as normal stools, and Cleveland Clinic calls them the most ideal. Neither is "better" than the other.
• Types 5 to 7, the fast side. Stool moved through quickly and did not lose as much water. Types 6 and 7 are what the Rome criteria count as loose stool.

Type 5 is the one sources disagree on. Cleveland Clinic groups it with Types 6 and 7; a 2016 validation study counted Types 3 to 5 as normal; a clinical review says Type 5 counts as loose only "to some degree." In practice, an occasional Type 5 after an ordinary day is common. A steady run of it is worth noticing.

Does your type really show your transit time?

Roughly, and best at the extremes. A review in the Journal of Clinical Medicine describes stool form as a rough stand-in for colon transit when stool sits at either end of the scale. In a multicenter study of adults with constipation, a type below 3 picked out slow whole-gut transit with 85% sensitivity and 82% specificity. The same study found no such link in healthy adults, while an earlier study of healthy volunteers on controlled diets did find hard stool tied to slow colon transit. So the honest summary is that the chart reflects what happened in your colon, and it is a signal, not a stopwatch.

It is a better signal than frequency, though. The same research that validated the chart found that how often someone goes is a poor guide to how fast things are moving. Shape carries more information than count.

What counts as normal?

Mostly Types 3 and 4, with regular exceptions. In a Swedish study of healthy adults who logged every bowel movement, about 77% of stools were normal in consistency, 12% were hard and 10% were loose. Cleveland Clinic puts it simply: a hard poop or a mushy poop now and then is normal.

Frequency varies widely too. In the same study, 98% of healthy adults went somewhere between three times a day and three times a week, and MedlinePlus notes that you do not need a bowel movement every day. What matters most is your own usual pattern, which is why one poop tells you much less than a week of them. A small 2021 study of healthy adults found that most of the variation in stool consistency happened within the same person from day to day, not between people. Our Learn article on why poop changes every day goes deeper.

What moves your type?

Stool form responds to ordinary inputs. The ones with real evidence behind them:

• Fiber, and which kind. For chronic constipation, the joint 2023 guideline from the American Gastroenterological Association and the American College of Gastroenterology found that among fiber supplements only psyllium appears to be effective. Psyllium can also firm up loose stool. Wheat bran improves bowel function in healthy people but can make diarrhea worse. Add fiber slowly: NIDDK and MedlinePlus both note that a sudden increase can bring bloating and gas.
• Fluids, when you are short on them. In a trial of constipated adults already eating a high-fiber diet, drinking 1.5 to 2 liters of water a day improved the fiber's effect. In healthy volunteers, extra water mostly produced extra urine. Water matters most when you are under-hydrated or adding fiber.
• Movement. A 2019 review of nine trials found exercise helped constipation symptoms, though the trials had a high risk of bias. NIDDK says regular physical activity may help.
• Coffee. About 29% of people in one study said coffee brought on the urge to go, and decaf worked too, so caffeine is not the whole story.
• Sugar alcohols. Sorbitol, mannitol and xylitol in sugar-free foods can cause diarrhea in some people (NIDDK). US rules require a "laxative effect" warning on foods likely to supply 50 grams of sorbitol a day.
• Medicines. Opioid pain medicines, iron supplements, antacids with aluminum or calcium, and some antidepressants are linked to constipation; antibiotics and antacids with magnesium to loose stool. Do not stop a medicine without talking to a clinician.
• Routine, travel and stress. NIDDK lists travel, changes in what you eat and ignoring the urge to go; the NHS adds stress and anxiety.
• The menstrual cycle. In one study of women taking oral contraceptives, stools were looser and more frequent on the first day of bleeding. In another, 28% reported diarrhea during their period.

Why matching your own poop is harder than it looks

Matching a stool to a chart sounds easy, and mostly it is. In a 2016 validation study, volunteers matched stool models to the right type about four times in five. The mistakes were not random, though: they clustered at the borders between Types 2 and 3 and between Types 5 and 6, exactly where the distinction matters most. A separate study found that even gastroenterology providers agreed less often at those same boundaries.

That is the case for a consistent read. When the same method types every stool, a shift from Type 4 to Type 5 over a week is a real change rather than a judgment call. It is also why clinicians ask for records over time: the American College of Gastroenterology's IBS guideline recommends daily diaries kept for two weeks. See how to keep a stool diary.

When to check in with a clinician

Most off days pass on their own. These are the signals sources agree deserve a conversation:

• On the slow side: constipation that does not improve with self-care, or a family history of colon or rectal cancer (NIDDK). Cleveland Clinic adds constipation lasting more than three weeks, or constipation that is new for you. See a doctor right away if it comes with bleeding from the rectum, blood in your stool, constant belly pain, being unable to pass gas, vomiting, fever, lower back pain or weight loss you cannot explain.
• On the fast side: for adults, diarrhea lasting more than two days, six or more loose stools in a day, a high fever, severe pain in the belly or rectum, stools that are black and tarry or contain blood or pus, or signs of dehydration (NIDDK).
• Any lasting change from your usual pattern. As MedlinePlus puts it, if your bowel habits change, check with your provider.

This chart describes adults. Children's stool is judged on modified scales, and their thresholds for diarrhea are shorter.

How Stoolio reads the Bristol scale

Stoolio turns the chart into a scan. Point your phone at the bowl, and one photo is matched against all seven Bristol types. The same scan returns 12 visual readings, including color, shape, size, consistency, fragmentation, and hydration and fiber cues, plus an estimated transit time and a Stoolio Score out of 100. Because every stool is read the same way, borderline calls stop being guesswork, and your trends show whether a change is a one-off or a pattern. When you need it, you can export a clean PDF or CSV summary to bring to an appointment.

It is a visual estimate, not a medical assessment, and it is private by default. Read more about finding your Bristol type with a scan and how the Stoolio Score works, or try the free What does my poop mean? checker first.

Sources

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29. US Code of Federal Regulations. 21 CFR 184.1835, Sorbitol.