How Scientists Count Farts, College

I’m farting for science!

Dr. Raven joins a fart study at the University of Maryland. She wears a sensor on her underwear for three days, and the sensor counts her farts by the hydrogen gas in them. Old counts said people fart 10 to 14 times a day, and the sensor study found far more.

A colorized electron microscope image of a cluster of oblong E. coli bacteria, magnified 10,000 times — Flatulent comes from New Latin *flātulentus*, formed from *flātus*.

Your word of the day is

FLAY-tus

fla-to blowfrom Latin flāre

-tusthe act offrom Latin -tus

Gas made in the intestines and passed out of the body. Flatus is the science word for the gas in a fart.

Australian researchers asked 6,416 people to log each fart in a phone app, as close as possible to the moment it happened, on at least 3 days.

Make a guess before you read the paper. How many farts a day do you think the average participant logged? Give your reason in one sentence.

Hint

In the video, Raven gives an old estimate of 10 to 14 a day and a sensor estimate about three times higher. Would counts that people tap into an app come out closer to the old estimate or to the sensor estimate?

A man reads printed papers at his desk beside a computer in 1987

Read the paper

Brindal and Baird, “Regular Flatulence Patterns Among Community-Dwelling Individuals in Australia,” JAMA Network Open, 2026. The paper is free to read.

Emily Brindal and Danielle Baird of Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) created a phone app called Chart Your Fart. From November 2024 to February 2025, 6,416 participants aged 14 and older logged 360,192 farts, each as close as possible to the moment it happened, for a mean of 10 days. The table below comes from the paper’s Table. It compares who joined with Australia’s population aged 14 and older, and it gives the farts logged per day. It leaves out the 146 participants in the paper’s Other gender group, which has no population figure.

Group	Share of sample, %	Share of Australian population, %	Farts logged per day, mean (SD)	Farts logged per day, median (IQR)
All participants	100	100	5.0 (3.8)	3.8 (2.5 to 6.2)
Female	50.7	50.7	4.8 (3.6)	3.8 (2.4 to 6.0)
Male	47.0	49.3	5.2 (3.9)	4.0 (2.5 to 6.5)
Age 14 to 25	13.3	17.7	4.4 (3.4)	3.3 (2.2 to 5.3)
Age 26 to 45	38.1	33.9	5.2 (3.8)	4.0 (2.6 to 6.5)
Age 46 to 65	38.7	29.2	5.0 (3.9)	4.0 (2.5 to 6.3)
Age 66 and older	10.0	19.2	4.8 (3.7)	3.7 (2.4 to 5.8)

People crossing a busy street in Melbourne, Australia, in golden light

A positive difference means a group made up more of the sample than of the population.

Which age group did the Chart Your Fart study oversample the most?

See the table

Group	Share of sample, %	Share of Australian population, %	Farts logged per day, mean (SD)	Farts logged per day, median (IQR)
All participants	100	100	5.0 (3.8)	3.8 (2.5 to 6.2)
Female	50.7	50.7	4.8 (3.6)	3.8 (2.4 to 6.0)
Male	47.0	49.3	5.2 (3.9)	4.0 (2.5 to 6.5)
Age 14 to 25	13.3	17.7	4.4 (3.4)	3.3 (2.2 to 5.3)
Age 26 to 45	38.1	33.9	5.2 (3.8)	4.0 (2.6 to 6.5)
Age 46 to 65	38.7	29.2	5.0 (3.9)	4.0 (2.5 to 6.3)
Age 66 and older	10.0	19.2	4.8 (3.7)	3.7 (2.4 to 5.8)

An older man and woman with gray hair walking arm in arm down a road

Which age group did the Chart Your Fart study undersample the most?

See the table

Group	Share of sample, %	Share of Australian population, %	Farts logged per day, mean (SD)	Farts logged per day, median (IQR)
All participants	100	100	5.0 (3.8)	3.8 (2.5 to 6.2)
Female	50.7	50.7	4.8 (3.6)	3.8 (2.4 to 6.0)
Male	47.0	49.3	5.2 (3.9)	4.0 (2.5 to 6.5)
Age 14 to 25	13.3	17.7	4.4 (3.4)	3.3 (2.2 to 5.3)
Age 26 to 45	38.1	33.9	5.2 (3.8)	4.0 (2.6 to 6.5)
Age 46 to 65	38.7	29.2	5.0 (3.9)	4.0 (2.5 to 6.3)
Age 66 and older	10.0	19.2	4.8 (3.7)	3.7 (2.4 to 5.8)

A calculator and a pen on a sheet of paper

Australia’s population shares for the four age groups are 17.7, 33.9, 29.2 and 19.2 percent, and the groups logged means of 4.4, 5.2, 5.0 and 4.8 farts a day.

Weighted to match Australia’s population, the four Chart Your Fart age-group means give a mean of ____ farts a day.

See the table

Group	Share of sample, %	Share of Australian population, %	Farts logged per day, mean (SD)	Farts logged per day, median (IQR)
All participants	100	100	5.0 (3.8)	3.8 (2.5 to 6.2)
Female	50.7	50.7	4.8 (3.6)	3.8 (2.4 to 6.0)
Male	47.0	49.3	5.2 (3.9)	4.0 (2.5 to 6.5)
Age 14 to 25	13.3	17.7	4.4 (3.4)	3.3 (2.2 to 5.3)
Age 26 to 45	38.1	33.9	5.2 (3.8)	4.0 (2.6 to 6.5)
Age 46 to 65	38.7	29.2	5.0 (3.9)	4.0 (2.5 to 6.3)
Age 66 and older	10.0	19.2	4.8 (3.7)	3.7 (2.4 to 5.8)

Bar charts and pie charts printed on a report

Would weighting the Chart Your Fart age groups to match Australia’s population move the mean of 5.0 farts a day by much?

See the table

Group	Share of sample, %	Share of Australian population, %	Farts logged per day, mean (SD)	Farts logged per day, median (IQR)
All participants	100	100	5.0 (3.8)	3.8 (2.5 to 6.2)
Female	50.7	50.7	4.8 (3.6)	3.8 (2.4 to 6.0)
Male	47.0	49.3	5.2 (3.9)	4.0 (2.5 to 6.5)
Age 14 to 25	13.3	17.7	4.4 (3.4)	3.3 (2.2 to 5.3)
Age 26 to 45	38.1	33.9	5.2 (3.8)	4.0 (2.6 to 6.5)
Age 46 to 65	38.7	29.2	5.0 (3.9)	4.0 (2.5 to 6.3)
Age 66 and older	10.0	19.2	4.8 (3.7)	3.7 (2.4 to 5.8)

A December calendar page with the days crossed out

The Chart Your Fart app couldn’t tell a day with no farts apart from a day the participant forgot to log, and participants had no way to report a day with zero farts.

If some participants had days with zero farts, how would leaving those days out change the Chart Your Fart study’s mean?

See the table

Group	Share of sample, %	Share of Australian population, %	Farts logged per day, mean (SD)	Farts logged per day, median (IQR)
All participants	100	100	5.0 (3.8)	3.8 (2.5 to 6.2)
Female	50.7	50.7	4.8 (3.6)	3.8 (2.4 to 6.0)
Male	47.0	49.3	5.2 (3.9)	4.0 (2.5 to 6.5)
Age 14 to 25	13.3	17.7	4.4 (3.4)	3.3 (2.2 to 5.3)
Age 26 to 45	38.1	33.9	5.2 (3.8)	4.0 (2.6 to 6.5)
Age 46 to 65	38.7	29.2	5.0 (3.9)	4.0 (2.5 to 6.3)
Age 66 and older	10.0	19.2	4.8 (3.7)	3.7 (2.4 to 5.8)

A wooden bowl filled with chicken, rice and beans

Chart Your Fart logging peaked between 6 and 10 pm, when Australians eat the most food energy and fiber.

Which mechanism could link the evening peak in logged farts to food eaten earlier in the day?

See the table

Group	Share of sample, %	Share of Australian population, %	Farts logged per day, mean (SD)	Farts logged per day, median (IQR)
All participants	100	100	5.0 (3.8)	3.8 (2.5 to 6.2)
Female	50.7	50.7	4.8 (3.6)	3.8 (2.4 to 6.0)
Male	47.0	49.3	5.2 (3.9)	4.0 (2.5 to 6.5)
Age 14 to 25	13.3	17.7	4.4 (3.4)	3.3 (2.2 to 5.3)
Age 26 to 45	38.1	33.9	5.2 (3.8)	4.0 (2.6 to 6.5)
Age 46 to 65	38.7	29.2	5.0 (3.9)	4.0 (2.5 to 6.3)
Age 66 and older	10.0	19.2	4.8 (3.7)	3.7 (2.4 to 5.8)

A woman using her smartphone on a sofa between green plants

Besides gut chemistry, what could produce an evening peak in logged farts?

See the table

Group	Share of sample, %	Share of Australian population, %	Farts logged per day, mean (SD)	Farts logged per day, median (IQR)
All participants	100	100	5.0 (3.8)	3.8 (2.5 to 6.2)
Female	50.7	50.7	4.8 (3.6)	3.8 (2.4 to 6.0)
Male	47.0	49.3	5.2 (3.9)	4.0 (2.5 to 6.5)
Age 14 to 25	13.3	17.7	4.4 (3.4)	3.3 (2.2 to 5.3)
Age 26 to 45	38.1	33.9	5.2 (3.8)	4.0 (2.6 to 6.5)
Age 46 to 65	38.7	29.2	5.0 (3.9)	4.0 (2.5 to 6.3)
Age 66 and older	10.0	19.2	4.8 (3.7)	3.7 (2.4 to 5.8)

A lab technician reviewing DNA sequencing data on a computer

The app participants logged a mean of 5.0 farts a day. The Smart Underwear study, which used a hydrogen sensor, found a mean of 32.

The Smart Underwear mean of 32 farts a day is ____ times the Chart Your Fart app mean of 5.0.

See the table

Group	Share of sample, %	Share of Australian population, %	Farts logged per day, mean (SD)	Farts logged per day, median (IQR)
All participants	100	100	5.0 (3.8)	3.8 (2.5 to 6.2)
Female	50.7	50.7	4.8 (3.6)	3.8 (2.4 to 6.0)
Male	47.0	49.3	5.2 (3.9)	4.0 (2.5 to 6.5)
Age 14 to 25	13.3	17.7	4.4 (3.4)	3.3 (2.2 to 5.3)
Age 26 to 45	38.1	33.9	5.2 (3.8)	4.0 (2.6 to 6.5)
Age 46 to 65	38.7	29.2	5.0 (3.9)	4.0 (2.5 to 6.3)
Age 66 and older	10.0	19.2	4.8 (3.7)	3.7 (2.4 to 5.8)

A smartwatch worn on a person's left wrist

Which study design would measure how many farts a self-report app misses?

See the table

Group	Share of sample, %	Share of Australian population, %	Farts logged per day, mean (SD)	Farts logged per day, median (IQR)
All participants	100	100	5.0 (3.8)	3.8 (2.5 to 6.2)
Female	50.7	50.7	4.8 (3.6)	3.8 (2.4 to 6.0)
Male	47.0	49.3	5.2 (3.9)	4.0 (2.5 to 6.5)
Age 14 to 25	13.3	17.7	4.4 (3.4)	3.3 (2.2 to 5.3)
Age 26 to 45	38.1	33.9	5.2 (3.8)	4.0 (2.6 to 6.5)
Age 46 to 65	38.7	29.2	5.0 (3.9)	4.0 (2.5 to 6.3)
Age 66 and older	10.0	19.2	4.8 (3.7)	3.7 (2.4 to 5.8)

A hand-drawn line graph on paper with a metal ruler and two pens

Brindal and Baird’s table summarizes 360,192 farts logged by 6,416 people.

Which summary fits the Brindal and Baird table?

A digital clock glowing in a dark room late at night

Which question can’t the Brindal and Baird table answer?

Dried beans in many colors at a farmers market

Lesson complete

Today’s word

flatus

FLAY-tus

Gas produced in the intestines, partly by bacterial fermentation of undigested food, and passed through the anus.

Back to the lesson Start over

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Sources

Santiago Botasini, Brantley Hall and colleagues, University of Maryland, Biosensors and Bioelectronics: X, 2025
Brantley Hall’s lab, University of Maryland, ClinicalTrials.gov, NCT07134543
Michael Levitt, Digestive Diseases and Sciences, 1979
J. K. Furne and Michael Levitt, Digestive Diseases and Sciences, 1996
J. Tomlin, C. Lowis and N. W. Read, Royal Hallamshire Hospital, Sheffield, UK, Gut, 1991
Emily Brindal and Danielle Baird, CSIRO, Australia, JAMA Network Open, 2026
I. Rowland, G. Gibson, A. Heinken, K. Scott, J. Swann, I. Thiele and K. Tuohy, European Journal of Nutrition, 2018
N. W. Smith, P. R. Shorten, E. H. Altermann, N. C. Roy and W. C. McNabb, Gut Microbes, 2019
University of Maryland, “UMD Scientists Create ‘Smart Underwear’ to Measure Human Flatulence”, February 11, 2026
Human Flatus Atlas, the study’s enrollment site
Vision and Change core concepts and competencies, as summarized in Brownell and others, CBE Life Sciences Education, 2014
Word origins from Dictionary.com: flatus, inflate, inflation, conflate, flatulent, microbiome, micro-, bio-, biome, -ome, microbe
Spanish and Italian words from Wiktionary: inflar, fiato
Video quotes from YouTube’s auto-generated captions

How Scientists Count Farts, College

I’m farting for science!

Your word of the day is

Make a guess before you read the paper. How many farts a day do you think the average participant logged? Give your reason in one sentence.

Read the paper

Which age group did the Chart Your Fart study oversample the most?

Which age group did the Chart Your Fart study undersample the most?

Weighted to match Australia’s population, the four Chart Your Fart age-group means give a mean of ____ farts a day.

Would weighting the Chart Your Fart age groups to match Australia’s population move the mean of 5.0 farts a day by much?

If some participants had days with zero farts, how would leaving those days out change the Chart Your Fart study’s mean?

Which mechanism could link the evening peak in logged farts to food eaten earlier in the day?

Besides gut chemistry, what could produce an evening peak in logged farts?

The Smart Underwear mean of 32 farts a day is ____ times the Chart Your Fart app mean of 5.0.

Which study design would measure how many farts a self-report app misses?

Which summary fits the Brindal and Baird table?

Which question can’t the Brindal and Baird table answer?

Lesson complete

Today’s word

Look at these again