Personal question: would you say you're a frequent farter? On average a day, how many backside burps are you responsible for: five? 20? More?
There are no bum answers, because scientists recently discovered that our textbooks are surprisingly empty when it comes to human flatulence.
Medical literature often claims that the average person passes wind 5–15 times a day, but those estimates are based on limited research from the 1980s, says Prof Brantley Hall, who studies the human gut microbiome at the University of Maryland in the US.
“There are a couple of studies, but they were pretty invasive. They involved rectal tubes,” he says. “We really haven’t advanced our understanding since then.”
Until now, that is. Hall and his team are building what they call the Human Flatus Atlas to map the normal range of flatulence in our species. Central to this mission is newly developed smart underwear that detects human exhaust fumes.
A coin-sized sensor is clipped discreetly into a standard pair of briefs. There, it detects gas leaks around the clock and sends corresponding data to an app for users or researchers to track their flatulence.
In a study published in December 2025 in Biosensors and Bioelectronics: X, 38 participants wore the smart pants for more than 11 hours a day for a minimum of three days. The sensors revealed that people fart more often than we previously thought.
Healthy adults produce an average of 32 farts a day, although the median number doesn’t tell the whole story.
It turns out there’s significant variety from one bottom to the next. In the study, participants ranged from four farts a day to as many as 59. Unpublished data from ongoing studies show an even greater range.
“We had one person farting 175 times a day,” Hall says. “Then another person – on the same diet – only farted four times.”
The seat of your pants
These nostril-twitching insights are down to the technology that the team has spent five years perfecting.
Hall laughs as he explains the origin story. “I’m a microbiologist and we were studying microbial metabolism one day in an anaerobic chamber,” he says.
“Things weren’t working. We got frustrated and we took the sensor out of the chamber and someone farted on it – and we had this amazing signal!”
Since that fateful day, the sensor has gone where no wearable has gone before – inside your pants. It detects hydrogen, one of the gases produced when the bacteria in our guts metabolise food.
There are also other gases in the mix and Hall hopes to capture them in future versions, but the current technology only detects ‘H-bombs’.
That’s enough for researchers to measure the frequency of flatulence and begin piecing the Human Flatus Atlas together. Hall says the team’s studies are oversubscribed with participants, which is testament to the time they spent making sure the device was comfortable to wear.
“The most unexpected thing is that there’s space in that area,” he says. “You won’t feel it. We tried many shapes, many materials. It turns out a circle is the right shape, because there’s no wrong way to wear it.”
He holds up what he calls a ‘butt mannequin’ on our video call to show where the sensor is located. “It goes there,” he says, pointing, “adjacent to the perineum. There’s space there. When you sit down, it’s not actually touching you.
“And, you know, women apply menstrual pads to their underwear and they deal with it just fine. Our device is much smaller than the average menstrual pad.”
Read more:
Sniff test
The more that people wear Hall’s smart underwear, the more we’ll learn about an everyday bodily function that – for all the sniggers at the back of the classroom – can tell us a lot about our gastrointestinal health.
For the most part, farting is completely normal and healthy. In fact, people who eat healthy diets with lots of fibre are among the most frequent farters, because extra gas is produced when fibre-rich foods like legumes and vegetables are fermented in the gut.
Flatulence is a useful signal for general guthealth. It can be a symptom of irritable bowel syndrome or food intolerances.
Changes in habits or frequency might suggest shifts in your microbiome, which can be linked to increased stress or issues with your diet. Excessive (or excessively smelly) gas can be a sign that you’re lactose or gluten intolerant.
And if your farts are regularly accompanied by other symptoms, like diarrhoea, pain or bloating, then it’s worth a visit to your GP.
Differences in farting can be caused by a number of factors, Hall says. “Human genetics, diet and microbiome all affect how we fart and how often we fart. Let’s say you’re lactose intolerant, that would be a genetic input,” he says.
“But if you’re lactose intolerant, you have to stack diet on top because if you drink milk you’re going to fart more.”
Hall believes that smart pants technology can be another empowering way for people to track their health, but it also gives doctors more data to help their patients.
“We don’t have medical approval for this right now, so it’s for research use only. But in the future, we’d love for clinicians and gastroenterologists to be able to look at this data to inform their decisions. To know what’s abnormal, you have to understand what normal is.”
Hall hopes we’ll get to a stage where we could all have a kind of fart score that tells us about our health, a bit like cholesterol levels or blood pressure do today.
One of the next stages will be to add methane detection, which is clinically associated with constipation. Then the team hopes to go international and find out how other countries’ farting habits line up with America’s.
Don’t you just love the smell of progress in the morning?
Read more:
