Is National Fart Day the same as National Pass Gas Day?

No, they are different days. National Fart Day is February 5 and leans into the biology and science of digestion, while National Pass Gas Day is January 7 and leans into the culture and history of the subject.

Why does a fart smell if most of it is odorless?

More than 99 percent of a fart is odorless gas, but a trace of sulfur compounds under one percent of the volume carries the smell. Hydrogen sulfide, the rotten-egg gas, is the main offender.

How many times a day is it normal to pass gas?

Estimates from medical sources commonly fall in the range of about 14 to 25 times a day, which is a normal part of digestion. Frequency varies with diet and the mix of microbes in your gut.

National Fart Day

Next celebratedFriday, February 5, 2027

A lighthearted observance on February 5 that turns a universal bit of human biology into an occasion to learn how digestion actually works.

See how to celebrate

Countdown to the day

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Last updated March 21, 2026 · by the Holiday Calendar TeamHave an update or spot an error?

YEARLY DATEFebruary 5

OBSERVED INUnited States

CATEGORYFun

SUBCATEGORYSilly

ORIGIN

Community Origin

FOUNDING ENTITY

Not documented

FIRST OBSERVED

Not documented

HOW THE HOLIDAY CAME TO BE

A funny day with a serious science bench.

No founder, no establishing proclamation, and no documented reason the day falls on February 5 could be found. National Fart Day circulates as an internet-era humor observance with no primary establishment record, so its origin is treated as undocumented rather than invented.

+ Know the story? Submit a founder Help us complete this holiday

INTRO

The part you smell is less than one percent of it

Here is the strange truth at the center of National Fart Day: the part that makes you wrinkle your nose is the smallest part of all. By volume, a fart is almost entirely odorless gas. The smell rides in on trace compounds that make up well under one percent of what leaves the body.

That one percent is mostly sulfur. When researchers Fabian Suarez, John Springfield and Michael Levitt collected and measured human flatus for a 1998 study in the journal Gut, they found that hydrogen sulfide, the same gas that gives rotten eggs their reputation, was the dominant odor-causing component. The worse a sample smelled, the more hydrogen sulfide it held.

So this February 5 day is built on a small joke and a real science. The joke is universal and needs no explanation. The science, the chemistry and biology of digestion, is genuinely surprising, and most of it is hiding in plain sight inside everyone.

ORIGINS

Fart Day history

INTRODUCTION

National Fart Day has no founder on record and no documented reason it landed on February 5. What it does have is a subject with a real research history, and that history is far more interesting than the day's murky beginnings.

For most of human history, gut gas was a punchline, not a question. The shift toward studying it seriously is recent, and it runs largely through one laboratory.

CHAPTER 01

The man who made flatus a science

Gastroenterologist Michael Levitt spent decades treating gut gas as a measurable subject rather than a joke. By the time the field matured, Levitt had led flatulence research for years, building the methods others would use.

His group's approach was unglamorous and exact: collect the gas, separate it, and measure each component. That turned vague assumptions into numbers.

CHAPTER 02

Why beans earned their reputation

Beans and certain vegetables carry sugars called raffinose and stachyose, held together by bonds the human gut cannot cut. People simply lack the enzyme alpha-galactosidase needed to break them.

So those sugars travel undigested into the colon. There, gut bacteria ferment them into hydrogen, carbon dioxide and methane, which is why a bean-heavy meal announces itself later.

CHAPTER 03

From guesswork to hard numbers

In 1991, a team led by Read measured normal output directly. Volunteers on a fiber-free diet produced far less gas, with the median dropping to about 214 ml over 24 hours, proof that much of the volume is fermentation, not swallowed air.

Seven years later came the odor study. Working with 16 volunteers fed pinto beans, Levitt's group pinned the smell on sulfur gases and named hydrogen sulfide the chief culprit. The punchline subject had finally been measured, and the lab settled what a fart is actually made of.

WHY THIS DAY MATTERS

Why We Love National Fart Day

BIOLOGY

A fart is mostly a report from your gut bacteria.

Roughly three-quarters of flatus is hydrogen, carbon dioxide and methane produced by gut bacteria, not swallowed air. That makes a fart a readout of fermentation happening in the colon, not just a leak of what you breathed in.

HEALTH

Gas can be a useful signal

Flatulence is usually normal, but Cleveland Clinic notes that excessive or persistent gas can point to conditions like celiac disease, irritable bowel syndrome, lactose intolerance or SIBO. It is general information worth knowing, not a reason to worry about an ordinary day.

EDUCATION

A joke that opens a real lesson

The subject is universal and disarming, which makes it an unusually easy way to teach how the digestive system works. A day built on a laugh becomes a door into chemistry most people never learned.

BY THE NUMBERS

National Fart Day by the Numbers

~14/day: Times a healthy adult passes gas
476-1491 ml: Daily flatus volume measured over 24 hours
~1 in 3: People whose gut makes methane
1.06 umol/l: Hydrogen sulfide, the lead smell gas
5 gases: Main odorless gases in flatus

GET INVOLVED

How to Celebrate National Fart Day

Learn what your gut actually does

Read a plain-language explainer on how digestion turns food into gas in the colon. Understanding the chemistry makes the day funnier and a lot more interesting.

RUN

Run a friendly bean experiment

Cook a meal built around beans or cruciferous vegetables and notice the timing. The delay between dinner and effect is fermentation by your gut bacteria at work.

TRY

Try a fiber-free day for contrast

Compare a high-fiber meal with a low-fiber one and see how your body responds. A 1991 study found a fiber-free diet sharply cut measured daily gas.

Share one fact that surprises people

Tell a friend that the part of a fart you can smell is a tiny sulfur trace, not the bulk of it. It is the rare science fact that doubles as a great party line.

READ

Read up on digestive health

Browse general information from a trusted source like Harvard Health to separate normal gas from a reason to ask a doctor. Knowing the difference is the most useful takeaway of the day.

Test your knowledge

How well do you know National Fart Day?

1 / 8

Roughly how much of a fart, by volume, is odorless?

GOOD TO KNOW

Surprising facts about National Fart Day

The smelly part measures in parts per million

The sulfur compounds behind the odor are present at tiny concentrations, on the order of tens of parts per million per fart, yet that trace is all the nose needs.

Methane comes from microbes that are not bacteria

The methane in some people's gas is made by archaea, an ancient branch of life, chiefly Methanobrevibacter smithii, the gut's dominant methane producer.

Beano works by lending you an enzyme

The anti-gas product supplies alpha-galactosidase sourced from the mold Aspergillus niger, the very enzyme humans lack.

Three sulfur gases share the blame

Beyond hydrogen sulfide, methanethiol smells of rotten cabbage and dimethyl sulfide is oddly sweet, the trio that chemists pin the odor on.

A 19th-century star performed with this biology

Joseph Pujol, billed as Le Petomane, headlined the Moulin Rouge from 1892 using remarkable abdominal control, among the highest-paid performers of his day.

GET INVOLVED