Interactive Tool

Bristol Stool Chart

Tap any of the 7 types to see what it means, how long it's been in transit, and whether it's worth worrying about. The scale gastroenterologists actually use.

Developed at the University of Bristol. Used worldwide in IBS diagnosis, FDA drug trials, and stool diaries.

Type 1 - Separate hard lumps

~65h transit time Constipation zone

What it means

The longest transit time on the Bristol scale. Your colon held the stool so long it absorbed most of the water, leaving it dry and compacted. This is classic constipation.

Common causes

  • Dehydration
  • Low fiber intake, especially soluble fiber
  • Sedentary lifestyle
  • Opioid pain medication
  • Iron supplements

Verdict

Concerning if it's your normal. Increase water, add soluble fiber (oats, psyllium, chia), and move more. If it lasts more than two weeks, talk to your doctor.

Log a Type 1 in the Number Two app →

Type 2 - Lumpy sausage

~55h transit time Slow zone

What it means

Still slow transit. The stool formed as a single lumpy mass rather than breaking into separate pieces, but it's been in the colon long enough that too much water was absorbed. Borderline constipation.

Common causes

  • Not enough water
  • Low-fiber diet, especially soluble fiber
  • Ignoring the urge to go
  • Stress
  • Some antidepressants and blood pressure medications

Verdict

Not urgent, but not ideal. If it's your usual, start with hydration and soluble fiber before anything stronger.

Log a Type 2 in the Number Two app →

Type 3 - Sausage with cracks

~45h transit time Healthy zone

What it means

One of the two ideal shapes. Firm enough to hold together, soft enough to pass without straining. Transit time is right in the middle of the healthy window.

Common causes

  • Balanced fiber intake
  • Adequate hydration
  • Regular movement
  • Consistent meal timing

Verdict

Healthy. Whatever you're doing, keep doing it.

Log a Type 3 in the Number Two app →

Type 4 - Smooth, soft sausage

~35h transit time Ideal zone

What it means

The gold standard. Every gastroenterologist wants to see this. Optimal water content, smooth form, easy to pass with no strain. Your gut is moving at exactly the right pace.

Common causes

  • Well-balanced diet with soluble and insoluble fiber
  • Consistent hydration throughout the day
  • Regular physical activity
  • Good stress management
  • Enough sleep

Verdict

Ideal. This is the target.

Log a Type 4 in the Number Two app →

Type 5 - Soft blobs with clear edges

~25h transit time Borderline zone

What it means

Passing a bit too quickly. Your colon didn't have quite enough time to absorb water, but the stool is still distinct and hasn't crossed into diarrhea. Think of it as your gut trending fast.

Common causes

  • Mild food sensitivity
  • Excess caffeine
  • Stress or anxiety
  • Too much insoluble fiber at once
  • Artificial sweeteners (sorbitol, xylitol)

Verdict

Not diarrhea, not ideal. Worth noticing but not alarming. If it becomes your pattern, track what you're eating and drinking.

Log a Type 5 in the Number Two app →

Type 6 - Fluffy, mushy pieces

~15h transit time Diarrhea zone

What it means

Transit is significantly faster than normal. Your colon barely had time to absorb water. This is mild to moderate diarrhea.

Common causes

  • Viral or bacterial infection
  • Food intolerance (lactose, gluten, FODMAPs)
  • IBS-D (diarrhea-predominant IBS)
  • Antibiotics
  • High-stress period
  • Food poisoning

Verdict

Concerning if it lasts more than a day or two. Stay hydrated with electrolytes. If it persists past 48 hours, or you see blood, talk to a doctor.

Log a Type 6 in the Number Two app →

Type 7 - Entirely liquid

~5h transit time Urgent zone

What it means

The fastest transit possible. Your body is flushing itself out with almost no water reabsorption. Severe diarrhea carries a real risk of dehydration.

Common causes

  • Food poisoning
  • Viral gastroenteritis (stomach flu)
  • Bacterial infection
  • Inflammatory bowel disease (Crohn's, ulcerative colitis)
  • Severe food reaction
  • Medications like laxatives or antibiotics

Verdict

See a doctor if it lasts more than 24 hours, if you see blood, if there's fever, or if you're showing signs of dehydration (dark urine, dizziness, extreme thirst).

Log a Type 7 in the Number Two app →

Why transit time matters

Stool form is the single best indicator of how long food takes to pass through you. Firmer means slower. Looser means faster.

1
2
3
4
5
6
7
~65h (slow) ~35h (ideal) ~5h (fast)

Normal whole-gut transit averages 30 to 40 hours. Below that range, the colon can't absorb enough water; above it, it absorbs too much. Source: Lewis & Heaton, University of Bristol (1997).

Color matters too

Shape tells you about transit. Color tells you what else is going on. Six signals worth knowing.

BrownNormal digestion
GreenDiet or fast transit
YellowPossible malabsorption
BlackPossible GI bleed
RedHemorrhoid or bleed
PaleUrgent: bile duct

You're not alone

Digestive issues are not rare. They're the norm.

40%
of people worldwide have a functional GI disorder
Rome Foundation Global Study, 2021
45M
Americans live with IBS symptoms
American College of Gastroenterology
16%
of U.S. adults have constipation symptoms
NIDDK
1 in 3
women have a regular once-daily bowel habit
Heaton et al., 1992

When to see a doctor

Most changes are temporary and diet-related. But these warrant a medical consultation:

One bowel movement is a data point. A week of them is a pattern.

Number Two uses this exact Bristol scale for every log. No account. No tracking. Your data stays on your device.

Download for iOS - Free

Frequently asked questions

What is the Bristol Stool Chart?

The Bristol Stool Chart (officially the Bristol Stool Form Scale) is a seven-type classification system for stool form, developed at the University of Bristol by Dr. Kenneth Heaton and Dr. Stephen Lewis. It's the clinical standard gastroenterologists worldwide use to classify bowel movements, from Type 1 (hard lumps) to Type 7 (liquid).

Which Bristol type is healthiest?

Types 3 and 4 are both in the healthy range, with Type 4 (smooth, soft sausage) being the gold standard. Type 4 indicates optimal transit of around 35 hours, balanced hydration, adequate fiber, and healthy gut motility.

Is Type 5 diarrhea?

No. Type 5 is soft, distinct blobs with clear-cut edges. It signals transit is slightly fast and the colon didn't fully absorb water, but it hasn't crossed into diarrhea. Types 6 and 7 are considered diarrhea.

How do I go from Type 1 to Type 4?

Increase water intake, add soluble fiber (oats, psyllium, chia, fruits), move more throughout the day, and don't ignore the urge to go. Most people see improvement within a week or two. Persistent Type 1 stools lasting more than two weeks warrant a medical consultation.

What does Type 3 mean?

Type 3 is a healthy stool: sausage-shaped with visible surface cracks. Transit time is about 45 hours, within the healthy window. Along with Type 4, it's one of the two ideal types.

When should I see a doctor about my stool?

See a doctor if: constipation or diarrhea lasts more than two weeks, you see blood (bright red, dark, or black tarry), you have unexplained weight loss, stools are persistently pencil-thin, or you have severe abdominal pain with fever. Black tarry stools and pale/clay stools are urgent - seek medical care promptly.

How long does food take to become stool?

Normal whole-gut transit time is 30 to 40 hours, with an upper limit of about 70 hours. Transit time varies with stool form: Type 1 reflects about 65 hours, Type 4 about 35 hours, and Type 7 about 5 hours. Women generally have slightly longer transit times than men.

Is it normal to have different Bristol types on different days?

Yes. Some variation is normal - stool form shifts with diet, hydration, stress, sleep, and activity. What matters is your overall pattern, not any single bowel movement. Most healthy people land in Types 3-4 most of the time with occasional drift. Consistent drift into 1, 6, or 7 is worth tracking.