For something nearly everyone does every day, flatulence remains one of the least precisely measured human behaviors. Ask most people how often they pass gas, and you’ll likely get a snicker, a shrug, or a number that’s probably wrong.
Yet, scientists have now found a way to track someone’s farts continuously, objectively, and in real time—using what may be one of the most unconventional wearable devices ever created: smart underwear.
In a new study, published in Biosensors and Bioelectronics: X, researchers developed a wearable sensor system designed to measure hydrogen gas in flatus, offering a window into the hidden world of gut microbial activity.
The findings challenge long-held assumptions about how often people fart, opening a new frontier in microbiome research, where even the most awkward bodily functions can reveal meaningful insights about health.
Going back to that initial, seemingly silly question: how often does the average person pass gas in a day? According to researchers, far more than previously believed.
“We developed the Smart Underwear, the first wearable device that continuously measures hydrogen gas expelled in flatus, providing unprecedented temporal resolution of gut microbial activity,” researchers write. “The dramatic inter-individual variation and systematic under-reporting of flatus challenges existing assumptions about gas production and symptom perception.”
Rethinking What’s “Normal”
For decades, estimates of daily flatulence have relied largely on self-reporting. This method was always bound to be imprecise because people are not especially good at accurately tracking their farts.
“It is virtually impossible for the physician to objectively document the existence of excessive gas using currently available tests,” gastroenterologist Dr. Michael Levitt—affectionately nicknamed “Dr. Fart” or the “King of Farts”—once observed.
Based on self-reported data, past research has estimated that the average person’s daily fart count is roughly 10 to 20 episodes. However, the new study suggests those longstanding estimates may be too low.
In a week-long trial involving 19 participants, researchers used the smart underwear device and found that the average number of daily flatus events was 32, with some individuals experiencing as few as 4 and others as many as 59 per day.
That wide range highlights something scientists have long suspected but struggled to measure. There may be no such thing as a universal “normal” when it comes to gas production.
Instead, the data revealed dramatic variation between individuals—up to a 14-fold difference between the lowest and highest daily counts.
So, if you’ve ever wondered whether your own fart habits are “normal,” the takeaway is fairly reassuring. Anywhere from a handful to a few dozen times a day may still fall within the broad range of human variability.
Why We Fart in the First Place
Humans have apparently been laughing about farts for at least 4,000 years. The oldest recorded fart joke is widely believed to date back to the Sumerians around 1900 BC.
However, behind the toilet humor lies serious biology. Flatulence is not just a byproduct of digestion—it’s a direct output of the trillions of microbes living in the human gut.
When we eat, especially foods rich in complex carbohydrates or fiber, not all of it gets digested in the small intestine. The leftovers travel to the colon, where gut bacteria ferment them, producing gases such as hydrogen.
That hydrogen gas has two primary escape routes. It can be absorbed into the bloodstream and exhaled through the breath, or it can be expelled as flatus. Crucially, flatus contains dramatically higher concentrations of hydrogen, making it a far more sensitive signal of microbial activity.
In other words, every fart is a tiny data point about what your microbiome is doing.
However, capturing that data has historically been rather difficult. Traditional methods have included breath tests, stool sampling, or even invasive rectal tubes—none of which are suited for continuous, real-world monitoring.
The smart underwear developed by researchers in this latest study aims to solve that problem.
The device discreetly attaches to regular underwear via a snap system and contains electrochemical sensors that detect hydrogen gas. It continuously monitors flatus events, recording not just their frequency but also their duration and intensity.
In the study, participants wore the device during daily activities for up to a week, with most reporting high levels of comfort and compliance. On average, users wore the device for more than 11 hours per day.
While the concept may raise eyebrows or prompt a few jokes, the technology represents a serious advancement. By enabling continuous monitoring, researchers can now observe how gut microbes respond to diet, time of day, and other factors on an hour-by-hour basis.
Testing The “Smart Underwear”
To test whether the device could detect meaningful biological changes, researchers conducted an experiment with 38 participants using a controlled dietary intervention—known as the “GUMDROP” study.
Participants consumed either regular sugar-based gumdrops or gumdrops infused with inulin, a type of dietary fiber that humans cannot digest but gut microbes eagerly ferment.
In 94.7% of participants, the smart underwear detected increased hydrogen production after consuming the inulin gumdrops, confirming that the device could track real-time changes in microbial metabolism.
Interestingly, the increase in gas production often occurred several hours after consumption, reflecting the time it takes for fiber to reach the colon and undergo fermentation.
More Than Just a New Fart Joke
It’s easy to focus on the novelty and humor of wearable fart sensors. However, the implications could be significant.
The gut microbiome has been linked to everything from digestion and metabolism to immune function and mental health. Yet, researchers have struggled to measure its activity in real-world settings with high temporal resolution.
This new smart underwear technology could change that.
By providing continuous, non-invasive monitoring, smart underwear could help scientists better understand how diet affects the microbiome, why some people experience digestive discomfort, and how microbial activity varies throughout the day.
It could also pave the way for personalized nutrition strategies, where individuals adjust their diets based on real-time feedback from their gut.
So, How Do You Compare?
The study offers both reassurance and perspective. If you’ve ever wondered whether your daily gas output is “normal,” the answer is probably yes—across a surprisingly broad range. In other words, variability appears to be the rule rather than the exception.
However, researchers note there are still many unanswered questions in fart science. “We don’t actually know what normal flatus production looks like,” co-author and professor of Biological Sciences at the University of Maryland, Dr. Brantley Hall, said in a press release. “Without that baseline, it’s hard to know when someone’s gas production is truly excessive.”
To help answer that question, Hall’s lab is launching the Human Flatus Atlas, a nationwide effort that will use Smart Underwear to measure flatulence patterns day and night across hundreds of participants and compare those patterns with diet and microbiome composition.
Devices will be shipped directly to volunteers across the United States, allowing researchers to begin building an objective baseline for what “normal” gas production actually looks like.
More broadly, the effort underscores that even one of the most mundane—and embarrassing—human functions can offer a serious scientific window into health.
“We’ve learned a tremendous amount about which microbes live in the gut, but less about what they’re actually doing at any given moment,” Dr. Hall said. “The Human Flatus Atlas will establish objective baselines for gut microbial fermentation, which is essential groundwork for evaluating how dietary, probiotic, or prebiotic interventions change microbiome activity.”
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com