Bristol Stool Scale Explained
Understand the Bristol Stool Scale, a medical chart classifying stool into 7 types, used by doctors and IBS patients to track digestive health.
What is the Bristol Stool Scale?
The Bristol Stool Scale (also called the Bristol Stool Chart or Bristol Stool Form Scale) is a medical diagnostic tool designed to classify human stool into seven categories. It was developed at the Bristol Royal Infirmary in 1997 by Dr. Ken Heaton and Dr. Stephen Lewis and is widely used by gastroenterologists worldwide.
The scale helps patients and doctors communicate about bowel habits using a standardised system, removing guesswork and embarrassment from the conversation.
The 7 types
Type 1: Separate hard lumps
Small, hard, nut-like lumps that are difficult to pass. Indicates severe constipation and prolonged transit time (stool has been in the colon too long).
Type 2: Lumpy and sausage-shaped
Sausage-shaped but lumpy. Still indicates constipation, though less severe than Type 1.
Type 3: Sausage with cracks
Like a sausage but with cracks on the surface. Considered normal.
Type 4: Smooth and snake-like
Smooth, soft, sausage or snake-like. This is the ideal stool form, easy to pass and indicates healthy digestion and transit time.
Type 5: Soft blobs with clear edges
Soft blobs with clear-cut edges, passed easily. Slightly loose, may indicate a lack of fibre.
Type 6: Mushy with ragged edges
Fluffy pieces with ragged edges, mushy consistency. Indicates mild diarrhea.
Type 7: Entirely liquid
Watery with no solid pieces. Indicates severe diarrhea and very fast transit time.
What does each type mean?
| Type | Indication | Transit Time |
|---|---|---|
| 1-2 | Constipation | Slow (days) |
| 3-4 | Normal / ideal | Healthy (12-36 hours) |
| 5-6 | Tending toward diarrhea | Fast (hours) |
| 7 | Diarrhea | Very fast |
Why is it useful for IBS?
People with IBS often experience fluctuations between constipation (IBS-C), diarrhea (IBS-D), or both (IBS-M). Tracking stool type over time helps:
- Identify your IBS subtype: are you predominantly constipated, loose, or mixed?
- Spot triggers: correlate stool type changes with specific foods, stress, or sleep
- Measure treatment effectiveness: see if dietary changes or medications are helping
- Communicate with your doctor: share objective data instead of vague descriptions
How to track it
Consistency matters more than any single entry. Logging your Bristol type daily, even on normal days, builds the full picture. Over time, patterns emerge: you may notice that Type 6 stools always follow certain foods, or that stress consistently pushes you toward Type 1-2.
Flarely includes the Bristol Stool Scale as a built-in logging option for IBS. Each entry is timestamped and correlated with your food diary, sleep, stress, and other factors to help surface connections automatically.