What's Your Poop Type? The Bristol Stool Scale Will Show You

How your number two could in fact be anything from a number one to a number seven.

It’s interesting to reflect upon the range of big concepts in life that come in groups of seven.

There are The Seven Wonders of the World.

The Seven Deadly Sins.

The seven days of the week.

And, oh yes, the seven categories of human feces on the Bristol Stool Scale.

Wait, what?

That’s correct, we humans have an insatiable urge to classify things (in sevens, it seems, wherever possible) and it led a pair of British doctors to develop a stool scale back in 1997.

It defines the shape and consistency of bowel movements, the raw material that powers a hefty part of our work at uBiome.

Before we review this important work, however, let’s wind back the clock.

We’ll stay in Bristol though.

In 1978, Dr John Wyman and his colleagues at the Bristol Royal Infirmary set out to examine colonic transit time.

In other words, how long did it take food to make the journey from mouth, south, so to speak?

The scientists used a method devised in the 1960s by researchers at St Mark’s Hospital in London, who persuaded participants to swallow 25 radiopaque pellets of barium-impregnated polythene.


The research team collected stool samples from the participants and x-rayed them in order to spot and count the pellets.

In the 1978 experiments the colonic transit time was determined when 80% of the pellets had reappeared.

What happened to the other 20%?

Don’t ask.

Anyway, two main conclusions were drawn by Wyman et al.

First, there were striking variations in transit time.

The speediest among their 20 participants passed their pellets in a mere 34 hours.

The most laggardly however, took a full 128 hours.

One hundred and twenty eight hours.

Five days.

The study also collected data on stool size, and it was for here that Dr Wyman’s team reserved their most hyperbolic language, writing of the “extraordinary variation in the size of individual stools.”

This was a situation clearly crying out for some kind of classification system, and in 1986 Professor Gloria Davies at the University of Surrey didn’t disappoint, devising an eight-item scale which aimed to define stool consistency ranging from “loose, watery and runny” at No. 1, to “pellets like sheep droppings” at No. 8.

Once again, participants were recruited in order to provide poop samples for the good professor.

Thoughtfully, they were supplied with a little fresh-air spray to “minimise the problem of odor inherent in the collection of stools that are not passed into water.”

A nice touch, don’t you think?

Unfortunately for her, Professor Davies’ scale didn’t seem to catch on.

But 1997’s Bristol Stool Scale did.

Developed by Dr Stephen Lewis and Dr Ken Heaton at the University of Bristol, it classifies poop into seven types.

Perhaps seven was the magic number, rather than eight?

They also reversed the order of things, allocating a “1” to the pellet-like end, and a “7” to the soupy one.

Helpfully, the scale has appeared in illustrated form, making it an excellent way for patients to report on their bowel movements to doctors without needing to take in a sample.


Like being in a restaurant where you don’t speak the lingo, you just point at the appropriate picture.

Speaking of which, for research in other countries, the scale has even been translated by Buddhist monks into the Ladakhi language, spoken in the Leh district of Ladakh in India.

And in an effort to drag the scale into the 21st-century, a team at the Feinberg School of Medicine in Chicago commissioned 3-D printed models of the seven stool types, complete with a 10-inch-high model toilet in which they could be plopped.

Unfortunately, despite all their work the finished result was found to be no better than a printed chart at enabling people to label stool samples.

“What did you make at work today, dear?”

“A pile of poop.”

A children’s version of the Bristol Stool Scale has turned its seven types into quite, er, evocative descriptions: rabbit droppings, bunch of grapes, corn cob, sausage, chicken nuggets, porridge, and gravy.

Nice. But you do get the picture.

These days you can buy yourself a Bristol Stool Scale T-shirt or mug, for goodness sake.

And some enterprising home bakers have even rustled up chocolate cake versions of the scale, complete with seven appropriately-shaped stools on top, bringing a whole new meaning to the Chocolate Log.

I can’t close without mentioning a fascinating possible urban myth around the Bristol Stool Scale.

Google the term, and you’ll find dozens of pages reporting that it’s also known as the “Meyers Scale” in the UK, but nowhere is there any suggestion of why this should be.

After all, the two instigators of the work were named Lewis and Heaton, not Meyers.

Unfortunately Dr Ken Heaton passed away in 2013, but we were able to track down Dr Stephen Lewis.

Surely he, of all people, would help us make sense of the Meyers Scale mystery, we reasoned.

He got back to us mere minutes after we emailed him.

His answer?

“Sorry, no idea. Had not come across the term until you mentioned it.”

So who the heck was Meyers?

You know, perhaps we’ll never get to the bottom of it.

Further reading

3D interactive poop sculptures… you know, for kids!

Assessment of Commonly Used Pediatric Stool Scales: A pilot study

Bristol Stool Chart

Bristol Stool Form Scale Cake Recipe

Bristol stool scale

Stool form scale as a useful guide to intestinal transit time.

The Bristol Stool Form Scale (for children)

What your poop looks like can tell you how long it’s been inside.