If Everyone on Earth Farted at Once, It Would Fill 330 Olympic Pools. We Checked the Math.

Some questions science was never meant to answer. Then someone on Instagram answers them anyway. A simulation posted by the account @bob_justdidit has been making the rounds for asking what would happen if every person on Earth farted at exactly the same moment, and as UNILAD Tech reported, the answer involves Olympic swimming pools, Times Square and a comparison to Hiroshima.

It’s a ridiculous premise. But the numbers in the video are specific enough to check, so we did. The surprising part is that most of them hold up, and the real biology behind them is weirder than the joke.

What the simulation claims

The video scales up step by step. One fart is “only a hundred milliliters of gas,” but it carries hydrogen sulfide, which your nose can detect at around half a part per billion. That’s why a single one can take over an elevator. A class of 30 fills more than half a classroom. A stadium of 80,000 fans produces about 2,000 gallons of gas, enough that a bubble of it could lift a house cat, and if lit, would release the energy of about 20 pounds of TNT.

Scale that to New York City’s 8.5 million people and the bubble could lift a concert grand piano and go off like a ton of TNT over Times Square. Scale it to the whole planet and you get 330 Olympic pools of gas, a smell that could bury Manhattan almost half a mile deep, and an explosion equal to about a kiloton of TNT, or a fifteenth of the Hiroshima bomb.

We ran the numbers

Here’s what you get using the video’s own assumptions: 100 mL per person, half hydrogen, and the standard energy content of hydrogen gas, which is about 10.8 kilojoules per liter when it burns. That works out to roughly 540 joules per fart, about as much energy as a 60-watt light bulb uses in nine seconds, released all at once.

GeekBlog calculations. Assumes 100 mL per person, 50% hydrogen, hydrogen’s lower heating value, 1 kiloton of TNT = 4.184 terajoules, an Olympic pool = 2,500 m³, and Earth’s gravitational binding energy of about 2.2 × 10³² joules. Asteroid energy estimates vary widely.

So whoever made the video did their homework. The scaling is consistent from start to finish. The weak spot isn’t the arithmetic. It’s the starting assumptions.

What’s actually in a fart

Gastroenterologists have studied flatus in surprising detail, partly because excess gas is one of the most common reasons people see a doctor. The short answer is that farts are mostly odorless, and the mix changes a lot depending on who you are and what you ate.

That’s the key problem with the simulation. It assumes everyone’s gas is half hydrogen, which sits at the very top of the normal range. For a lot of people, especially those who swallow more air while eating or drinking fizzy drinks, it’s mostly nitrogen. And only some people carry the gut microbes, mainly a species called Methanobrevibacter smithii, that produce methane at all. Your personal fart chemistry depends heavily on your microbiome and your diet, especially beans, onions, broccoli and other foods rich in fiber your body can’t fully digest.

The smell, meanwhile, comes from a tiny fraction: sulfur compounds like hydrogen sulfide and methanethiol. Your nose is absurdly sensitive to them, which is why the simulation’s claim about smell spreading so far is plausible even though the quantity is minuscule. We couldn’t pin down the “half a mile over Manhattan” figure independently, since sulfur content varies even more than hydrogen does.

Could it actually explode?

Not the way the video implies. Hydrogen only ignites when it makes up roughly 4 to 75% of the air around it. A planet-wide fart wouldn’t form one neat bubble. It would come out of 8 billion people in different places and mix into the atmosphere almost immediately, diluting far below anything that could burn.

That said, gut gas can absolutely catch fire in the right conditions, and doctors take it seriously. There are documented cases of colonic gas igniting during colonoscopy procedures when electrical tools were used, which is why bowel prep is designed to avoid the kinds of sugars that make gut bacteria pump out extra hydrogen. And yes, the classic party trick with a lighter has sent people to the ER with burns. Don’t try it.

If you think gas is awkward on Earth, it’s a genuine engineering problem in space. Astronauts can’t open a window, so what happens when someone farts on the ISS involves filters, airflow and some surprisingly serious planning.

The twist: we already do this every day

Here’s the part the simulation leaves out. Studies that actually collected flatus from volunteers found the average person passes gas about 14 times a day, with each one averaging somewhere around 90 to 100 mL. The total comes to roughly 0.5 to 1.5 liters a day per person, with about 0.7 liters being typical.

In other words, the world quietly produces the equivalent of that apocalyptic simultaneous fart about seven times over, every single day. Nothing explodes, nobody’s buried under a smell cloud, and the atmosphere doesn’t notice. Spread out over time and space, it all just disperses.

And before anyone asks about climate change: human methane is a rounding error. Livestock are the big source, and that comes mostly from cows burping, not farting. A single cow can emit around 100 kilograms of methane a year, far more than any person.

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