The Bristol Stool Scale is a seven-point chart that classifies stool by shape and consistency. It was developed at the Bristol Royal Infirmary and published in 1997 by Stephen Lewis and Ken Heaton, and it has been the standard clinical shorthand ever since. When a clinician asks what things look like, this scale is the answer they're hoping you can give.
The reason it exists is practical: shape tracks transit time, which is how long food takes to travel through you. Slow transit dries things out. Fast transit doesn't give the colon time to absorb water. Shape is a readout of speed, and speed is a readout of how your gut is doing.
The seven types
1
Separate hard lumps
Significant constipation. Things are moving slowly and losing too much water on the way.
2
Lumpy and sausage-shaped
Mild constipation. Slow transit, but less severe than type 1.
3
Sausage-shaped with surface cracks
Normal. The healthy end of firm.
4
Smooth and soft, snake-like
Normal. The textbook answer, if textbooks were honest about what they were describing.
5
Soft blobs with clear edges
Borderline. Leaning quick, often a fibre question.
6
Mushy, ragged edges
Mild diarrhoea. Transit is running fast.
7
Entirely liquid
Diarrhoea. Nothing had time to form.
The original paper describes the types with food comparisons we will not repeat over your lunch break. Clinicians are braver than the rest of us.
What counts as normal
Types 3 and 4 are the normal range. Landing there most of the time suggests transit is in a healthy rhythm. Everyone visits the other types occasionally: a curry, a long flight, a stressful week. A single odd day is weather, not climate.
The pattern is what matters. A gradual drift from type 4 toward type 2 over several weeks tells you something a single reading never could, and that drift is exactly the kind of thing a daily record catches and memory does not.
When to talk to a doctor
- Blood, ever. That conversation should happen promptly.
- A persistent change from your normal that lasts more than a few weeks, in either direction.
- Type 6 or 7 alongside fever, severe pain, or signs of dehydration.
The Gut Brief is information, not diagnosis. A change on this scale is a reason to pay attention, and sometimes a reason to see a professional. It is never a diagnosis by itself.
How Verlow records it
Verlow's optional bowel log does not ask you to pick a number from one to seven. It asks whether things were harder or looser than usual, or about normal, and keeps that beside what you ate and how you trained. It does not colour it green or red, and it does not interpret it. If something on this scale worries you, the list above is the one to follow.