Estimation facts
Fermi and estimation questions quietly assume you know a few dozen real-world quantities. This is that list, scannable in ten minutes, built from the estimation problems candidates actually get asked, including the ones in our own bank. Skim it, notice which ones surprise you, and the estimation games stop feeling like trivia.
Values are rounded for interview use, not engineering. Practice applying them in the estimation games.
From our problem bank — the facts behind real asked questions
US gasoline burned~140B gal/yr ≈ 2.7B/week
…drivers · miles · mpg230M · 12k mi/yr · ~25 mpg
NYC coffee~10M cups/day
US chocolate~10 lb/person/yr ≈ 9M lb/day
Netflix US81M subs × ~$15.5 ≈ $15B/yr
Chicagocity 2.7M · metro 9.5M
Indonesia~280M (4th most populous)
La Liga season380 matches × ~2.6 goals ≈ 1,000
Willis Tower110 floors · 442 m · ~16k panes
Infinite Jest~1M sold · ~1,000 pages
Free fallh = ½gt², g≈9.8: 3 s ≈ 44 m
Mark-recaptureN ≈ caught × tagged / retagged
Classic Fermi anchors
US gas stations~115,000
US McDonald's / Starbucks~13.5k / ~16k
747 cabin volume~900 m³
Ping-pong ball volume~33 cm³ (→ ~20M per 747, ~64% packing)
School bus volume~70 m³
Golf ball volume~40 cm³
Pianos (US)~1 per 100 people; tuned ~1×/yr
A tuner tunes~4/day ≈ 1,000/yr (→ ~30 tuners in Chicago)
Reading speed~250 wpm ≈ 1 page/min
Ream of paper500 sheets, ~5 cm thick
US road deaths / yr~40,000
Hairs on a head~100,000
Cells in a human body~4 × 10¹³
Heartbeats in a lifetime~2.5 × 10&sup9;
US person-days per year335M × 365 ≈ 1.2 × 10¹¹
Shower / toilet flush~80 L / ~6 L
Distances & geography
Marathon42.2 km / 26.2 mi
Earth's circumference40,000 km
Earth's diameter12,700 km
Earth to Moon384,000 km
Earth to Sun150M km (1 AU)
New York to LA~4,000 km / 2,500 mi
New York to London~5,600 km
US East–West coast flight~5.5 hours
Degree of latitude111 km
Manhattan (length)~21.6 km / 13.4 mi
Heights & sizes
Statue of Liberty (with pedestal)93 m / 305 ft
Eiffel Tower330 m
Empire State Building443 m (with antenna)
Burj Khalifa828 m
Mount Everest8,849 m
Commercial cruising altitude~10–12 km
Story of a building~3 m / 10 ft
Door height~2 m
Credit card8.6 × 5.4 cm
Sheet of paper (US letter)21.6 × 27.9 cm
Olympic pool50 m × 25 m, ~2,500 m³
Football/soccer pitch~105 × 68 m, ~0.7 ha
Populations & people
World population~8.1 billion
United States~335 million
China~1.41 billion
India~1.44 billion
United Kingdom~68 million
New York City~8.3 million
London~9 million
US households~130 million
US births per year~3.6 million
Average human lifespan (global)~73 years
Human heart rate60–100 bpm
Breaths per minute (rest)~12–16
Speeds
Walking~5 km/h / 3 mph
Running (jog)~10 km/h
Usain Bolt (top speed)~44 km/h / 27 mph
Highway car~100–120 km/h
Commercial jet~900 km/h / 560 mph
Sound (in air)343 m/s ≈ 1,235 km/h
Light3 × 10⁸ m/s
Fast pitch / serve~160–250 km/h
Money & markets
US GDP~$28 trillion
World GDP~$105 trillion
US median household income~$75k
S&P 500 long-run return~10%/yr nominal
US equity market cap~$50 trillion
NYSE + Nasdaq daily volume~$500B traded
US federal budget~$6.5 trillion
Trading days per year~252
Everyday quantities
Cars in the US~290 million
US commercial flights per day~45,000
Piano keys / tuners in Chicago88 keys / ~100 tuners
Golf ball diameter4.3 cm
Ping-pong ball4.0 cm, 2.7 g
Grain of rice~25 mg
Standard deck / dice52 cards / 21 pips per die
Book page word count~300–400 words
Gallon of water3.8 L, 3.8 kg
Bathtub volume~150–200 L
Shower water use~10 L/min
Human daily calories~2,000–2,500 kcal
Handy math constants
√2, √3, √51.414, 1.732, 2.236
ln 2, ln 100.693, 2.303
e, π, π²2.718, 3.1416, 9.87
Seconds in a day / year86,400 / 3.15 × 10⁷
2¹⁰1,024 ≈ 10³
Rule of 72years to double ≈ 72 / rate%
1 in / 1 ft / 1 mi2.54 cm / 30.5 cm / 1.61 km
1 kg / 1 lb2.2 lb / 454 g
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