Let's Calc

Absurd questions, taken seriously.

How much energy does the rush-hour subway squeeze out of your ribcage? If a paycheck literally fell from the sky, how would the IRS classify it? Let's Calc runs everyday absurd questions through math, physics, economics, law, and statistics — and shows the working.

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Calculations grounded in physics, chemistry, biology, and the wider natural sciences

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Calculations involving prices, markets, taxes, debt, inflation, and economic intuition

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Everyday Life

Calculations about the absurd questions that pop up in daily life

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Calculations through the lens of law, policy, sociology, and statistics

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Calculations about human biology, calories, sleep, exercise, and medicine

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Calculations that zoom out to the planetary, galactic, or otherwise jaw-dropping scale

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Latest Calculations

How Much Would the Great Pyramid Cost to Build Today? Three Scenarios — and the Real Measure of Pharaonic Power
Money & Economy · Society & Law

How Much Would the Great Pyramid Cost to Build Today? Three Scenarios — and the Real Measure of Pharaonic Power

Three parallel calculations on what the Great Pyramid would cost in today's money: modern heavy equipment runs ~$1.5B; ancient hand-quarrying at global construction wages runs ~$22B; the grain rations Khufu actually paid convert to as little as $253M. But how much he 'underpaid' swings from 1× to 87× depending on how you value ancient labor — and the figure that doesn't move is the real measure of his power: locking 2.75% of the workforce onto one building for a generation.

#pyramid#construction cost#ancient Egypt#labor mobilization#economics#megaproject
How Many Times Must You Use a Tote Bag to Break Even?
Everyday Life · Society & Law

How Many Times Must You Use a Tote Bag to Break Even?

A cotton tote bag has a much larger production footprint than a plastic bag. The break-even point is 52–131 uses under GWP alone, or up to 7,100 uses if ozone depletion is factored in. Average real-world use? About 51 times. And individual savings amount to roughly one 89-billionth of the annual global production growth in carbon terms. Two reversals, one calculation.

#tote bag#carbon footprint#break-even#LCA#sustainability#policy
If the Spanish Armada Had Dropped a Plastic Bottle, Would It Be Gone by Now?
Physics & Science · Everyday Life

If the Spanish Armada Had Dropped a Plastic Bottle, Would It Be Gone by Now?

A PET bottle tossed into the English Channel during the Spanish Armada (1588) would still be intact today — with 12 years left on the clock. PET takes roughly 450 years to degrade in marine conditions, and that timeline gets much worse in a landfill. We calculate polymer breakdown timelines, the cube-law fragmentation math that turns one bottle into 18 trillion particles, and why NOAA still can't give you a definitive answer.

#plastic#decomposition#microplastics#environment#PET#polymer
Your One Ton of Plastic: How Much of Humanity's Plastic Is Actually Yours?
Everyday Life · Cosmic & Scale

Your One Ton of Plastic: How Much of Humanity's Plastic Is Actually Yours?

Since 1950, humanity has produced roughly 8.3 billion tonnes of plastic. Split evenly by world population, that comes to over a tonne per person — yet only 9% was ever recycled, and 886 kg of your share is sitting in a landfill or the ocean right now. We run the numbers and show how much the recycling rate actually matters.

#plastic footprint#plastic pollution#recycling rates#ocean plastic#environmental impact#per capita waste
One Elephant's Worth: How Much Stool Does a Human Produce in a Lifetime?
Body & Health · Everyday Life

One Elephant's Worth: How Much Stool Does a Human Produce in a Lifetime?

Over a lifetime, a human produces roughly 5,249 kg of stool — about the weight of an adult African elephant. We calculate what fraction of your daily calories exits unused, why a vegan diet scores 74% digestive efficiency while a low-fiber diet hits 93%, and what Kleiber's Law tells us about why mice produce more waste per kilogram than elephants.

#digestion#feces#energy efficiency#metabolism#lifespan
What Happens When You Buy Every Lottery Combination? A Full Cost-Benefit Analysis
Money & Economy

What Happens When You Buy Every Lottery Combination? A Full Cost-Benefit Analysis

Buying all 8.1 million Korean Lotto combinations costs about ₩8.1 billion (~US$6.0M). Even winning the jackpot solo doesn't cover it in a typical draw. Buying half looks like a 50/50 coin flip — but the loss when you miss is 3× the gain when you hit. We work out exactly when it becomes theoretically profitable and how big a Powerball jackpot you'd need.

#lottery#probability#economics#break-even#Korean Lotto#Powerball
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About Let's Calc

Let's Calc takes everyday absurd questions and oddball hypotheticals seriously. Each post draws on math, physics, economics, law, or statistics, and follows the signature [INPUT] / [FORMULA] / [OUTPUT] format — assumptions stated, working shown, punchline at the end.

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