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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Physics & Science

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

Can You Measure Faith in Joules? Marching Around Jericho 13 Times
Physics & Science

Can You Measure Faith in Joules? Marching Around Jericho 13 Times

The Book of Joshua describes six days of marching once around Jericho's walls, then seven laps on the seventh — 13 laps in all. How far did that add up to for one person, how long did it take, and how much metabolic energy did 40,000 marchers burn doing it? We reverse-engineer the city's size from archaeology, weigh three guesses at how far back from the wall they actually walked, and convert the total into joules — and, just for scale, into tons of TNT.

#Jericho#faith and physics#energy expenditure#Fermi estimation#ancient warfare
What's the True Cost of One Avocado? Water, Carbon, and Nutrition
Physics & Science · Everyday Life

What's the True Cost of One Avocado? Water, Carbon, and Nutrition

One avocado (100 g flesh) gets dissected through three lenses: water, carbon, and nutrition efficiency. The math checks the popular "200-320 liters of water" claim against the primary dataset, tests how much transport mode swings the carbon footprint, and ranks avocado's nutrient-per-liter efficiency against four other fruits.

#avocado#water footprint#carbon footprint#LCA#nutrition#sustainability
Gas, Diesel, Hybrid, or EV — Which Is Cheapest Over 5 Years? At 7, the Answer Flips
Money & Economy · Everyday Life

Gas, Diesel, Hybrid, or EV — Which Is Cheapest Over 5 Years? At 7, the Answer Flips

A car's sticker price is just the opening bid. Add in fuel, insurance, registration tax, maintenance, and resale value, and the total cost of ownership (TCO) tells a very different story. We run the numbers on a Hyundai Tucson in gasoline, diesel, and hybrid trims plus an IONIQ 5 EV — and the cheapest car changes not once but twice as ownership length and annual mileage shift.

#TCO#electric-vehicle#hybrid#diesel#gasoline#depreciation
How Much Will Sea Level Rise If Ice Melts?
Physics & Science · Cosmic & Scale

How Much Will Sea Level Rise If Ice Melts?

Adjust melt rates of Greenland ice sheet, Antarctic ice sheet, and mountain glaciers to calculate sea level rise directly. An interactive calculator covering IPCC low/high emission scenarios through complete melting, where you can explore different futures by adjusting sliders.

#climate change#sea level rise#ice sheet#Greenland#Antarctica#glacier melt
New York to Los Angeles: The Lowest-Energy Way to Travel?
Physics & Science · Everyday Life

New York to Los Angeles: The Lowest-Energy Way to Travel?

A 10 km commute by car uses far more energy per passenger than a bus — unless the bus is nearly empty. We break down energy intensity (MJ per passenger-km) across eleven transportation modes, from walking to electric cars to rockets, then apply it to one real trip — New York to Los Angeles, about 3,940 km (2,450 mi) — to see which one actually wins, and how badly occupancy and grid mix can reverse the rankings.

#energy#transportation#electric-vehicle#carbon-emissions#passenger-km#rocket
If a Global Flood Diluted the Ocean, Why Is It Still Salty? Three Models, and a Verdict for the Fish
Physics & Science · Cosmic & Scale

If a Global Flood Diluted the Ocean, Why Is It Still Salty? Three Models, and a Verdict for the Fish

If the whole world flooded with fresh water, why would the ocean still end up salty? We run three models side by side — a fixed-geography dilute-then-recover model, a Pangaea / catastrophic-tectonics back-calculation, and a third that asks whether the flood water itself was fresh or salty to begin with. None of the nine resulting scenarios leaves a salinity band where freshwater and saltwater fish could both survive.

#Noah's Ark#salinity#ocean#osmotic pressure#scripture#distillation
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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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