About the Bristol Stool Chart: History and Clinical Use
From Bristol Royal Infirmary to global clinical practice - Updated September 2026
The Origin: Bristol Royal Infirmary, 1997
The Bristol Stool Chart - formally the Bristol Stool Form Scale - came out of the University Department of Medicine at the Bristol Royal Infirmary, where Dr Ken Heaton was a reader in medicine. A seven-point stool form scale was already in use there by 1990, when Heaton and colleagues published O'Donnell LJ, Virjee J, Heaton KW, "Detection of pseudodiarrhoea by simple clinical assessment of intestinal transit rate", BMJ 300(6722):439-40. The paper that made the scale famous came seven years later, when Heaton and research registrar Dr Stephen Lewis published Lewis SJ, Heaton KW (1997), "Stool form scale as a useful guide to intestinal transit time", Scand J Gastroenterol 32(9):920-4. That 1997 study validated the scale rather than introducing it: its stated aim was to test whether the Bristol stool form scale responded to changes in transit time, because the lack of such evidence was keeping stool form scales out of practice.
The research context was gut transit time. Measuring how long food takes to pass through the digestive system is clinically important but impractical in routine practice - it traditionally required radio-opaque markers or scintigraphy. Heaton and Lewis observed that stool form (shape and consistency) closely correlated with colonic transit time, as measured by these techniques. Their insight was that a simple visual scale - requiring no equipment - could serve as a proxy for transit time assessment.
The 1997 study ran on 66 volunteers. Each had their whole-gut transit time measured with radiopaque marker pellets and their stools weighed, and each kept a diary recording their own stool form on the seven-point scale along with how often they went. The volunteers then took senna to speed transit up and loperamide to slow it down, and the whole set of measurements was repeated. Stool form tracked transit time better than either stool output or how often people went, both at baseline (r = -0.54) and, more importantly, in how it moved when transit changed (r = -0.65). Note what the design shows: the scores were self-reported by the volunteers, not graded by clinicians, which is exactly why the scale works as a patient-facing tool. The paper reports correlations rather than a lookup table of hours per type, so the transit-time bands given elsewhere on this site are an interpretive guide, not figures from Lewis and Heaton.
The scale was designed to be simple enough for patient self-report - a key practical advantage over objective transit measurement. This made it applicable far beyond the research setting: in primary care, gastroenterology clinics, care homes, clinical trials, and patient education.
Clinical Use: NHS, NICE, and Rome IV
Since its publication, the Bristol Stool Form Scale has been adopted widely in UK and international clinical practice:
The Rome Foundation's Rome IV criteria (2016), the global standard for functional gastrointestinal disorders, uses Bristol types directly to subclassify IBS. IBS-C requires more than 25% of stools being types 1-2; IBS-D requires more than 25% being types 6-7; IBS-M requires both thresholds. This places the scale at the centre of IBS management worldwide.
NICE guideline CG61 (Irritable bowel syndrome in adults) and various related guidelines reference the Bristol scale for patient assessment and monitoring. NICE's 2008 IBS guidance recommends patients keep a symptom diary that includes stool form as assessed by the Bristol scale.
NHS England published a plain-language Bristol Stool Chart for carers in July 2023, as an asset of its constipation campaign for people with a learning disability. NHS England describes it as a visual aid to help someone identify whether they are experiencing constipation, and its instruction is that a poo which does not look like type 3 or type 4 could be constipation. It is available as a free PDF from NHS England's website and is used well beyond the learning-disability setting it was written for.
The Bristol scale is used as an endpoint in clinical trials for laxatives, antidiarrhoeals, probiotics, and gastrointestinal medications. Its validated, standardised nature makes it suitable for measuring treatment response.
The scale has been translated into over 20 languages and is used by healthcare systems worldwide, including in the United States (where it is commonly called the Bristol Stool Scale), Australia, Japan, Germany, and across Europe. The Cleveland Clinic, Mayo Clinic, Stanford Medicine, and numerous gastroenterology societies all reference it.
About This Site
bristolstoolchart.com is an independent digital health reference project by Digital Signet. It is not affiliated with the NHS, Bristol Royal Infirmary, NICE, the Rome Foundation, Cleveland Clinic, or any other institution or clinical body.
The content of this site has been developed by referencing the original Lewis and Heaton 1997 paper, NHS England guidance, NICE clinical guidelines, and peer-reviewed gastroenterology literature. Content is reviewed against current NHS and NICE guidance before publication.
Our aim is to provide the best freely available consumer reference for the Bristol Stool Chart in the UK - more detailed than the official NHS PDF, more interactive than static reference pages, and written in British English with an NHS-appropriate tone. The interactive stool type selector and the private local-only tracker are the two features that distinguish this site from static references.
We are not doctors. This site does not provide medical advice. If you have a specific clinical concern, please consult your GP.
Readers can write to questions@
Updated September 2026