Daily estimation puzzle

Fermi Answer Today

Three questions. Three surprising answers. Reveal each answer when you’re ready, then see how Fermi estimates it.

Fermi #753 questions

A little help for today’s big questions.

1QUESTION 1 OF 3

How many days does a container ship take to sail from Shanghai to Rotterdam through the Suez Canal?

Reveal answer & explanation

Official answer

30

days

How to estimate it

Fermi’s official “Napkin math”

Shanghai to Rotterdam by sea is about half way around the world, say 20,000 kilometers. How fast does a giant cargo ship go? Maybe 30 km/h, about bike speed, which is roughly 700 kilometers a day.

Half way around the world
≈ 20,000 km
30 km/h × 24 hours
÷ 700 km a day
20,000 ÷ 700
≈ 29 days

Rounded assumptions may give a slightly different estimate. The official answer above is the game’s reference value.

Source calculation & reference
Shanghai to Rotterdam via Suez
≈ 10,600 nautical miles
Non-stop at 16 knots
≈ 27 days
Typical scheduled service, with a few port calls
28 to 32 days
≈
30 days

Reference cited by Fermi: Notteboom, Pallis & Rodrigue, Port Economics, Management and Policy: Routing Options between Shanghai, Rotterdam and New York

Full answer & compare your estimate
2QUESTION 2 OF 3

How many wild elephants lived in Africa at the last full continent-wide count, published in 2016?

Reveal answer & explanation

Official answer

415,000

elephants

How to estimate it

Fermi’s official “Napkin math”

Africa has about 50 countries, and most still have some wild elephants. Call it 35. How many in each? A few have huge herds and plenty have only a handful, so maybe 10,000 on average.

Countries with elephants
~35
Elephants per country
× 10,000
35 × 10,000
≈ 350,000

Rounded assumptions may give a slightly different estimate. The official answer above is the game’s reference value.

Source calculation & reference
IUCN African Elephant Status Report 2016, surveyed populations (data to end of 2015)
≈ 415,000 (± about 20,000)
Net loss since 2007, mostly to poaching
≈ 110,000
≈ result
415,000 elephants

Reference cited by Fermi: IUCN SSC African Elephant Specialist Group, African Elephant Status Report 2016

Full answer & compare your estimate
3QUESTION 3 OF 3

How many Oreo cookies are sold around the world each day?

Reveal answer & explanation

Official answer

164,000,000

Oreos

How to estimate it

Fermi’s official “Napkin math”

The easiest place to start is the US, about 330 million people. How many eat Oreos on a given day? Maybe 1 in 10, two cookies each. They sell everywhere, so call America a third of it.

Americans
330,000,000
1 in 10 eat 2 today
≈ 66,000,000
US is a third of the world
× 3
66M × 3
≈ 200,000,000

Rounded assumptions may give a slightly different estimate. The official answer above is the game’s reference value.

Source calculation & reference
Oreo cookies sold each year (Mondelez International)
≈ 60,000,000,000
Days in a year
÷ 365
60B ÷ 365
≈ 164,000,000

Reference cited by Fermi: Mondelez International, 2024

Full answer & compare your estimate

Fermi answer archive

Find a past question and explore the reasoning behind it.

Fermi #74
  1. 1.How many different names appear in the end credits of Avengers: Endgame (2019)?
  2. 2.How many of the 193 UN member countries have fewer people than New York City?
  3. 3.How many 12 oz (355 ml) soda cans could you fill with all the blood in an adult human body?
Fermi #73
  1. 1.How many oranges would it take to weigh as much as an adult male orangutan?
  2. 2.How many people holding hands would it take to circle the outside of the Colosseum in Rome?
  3. 3.How many atoms thick is a sheet of standard kitchen aluminum foil?
Fermi #72
  1. 1.How long would it take to listen to every country's national anthem back to back?
  2. 2.If the combined wealth of every billionaire on Forbes' 2026 list were split evenly among everyone on Earth, how much would each person get?
  3. 3.What is the world record for the most skips of a single stone thrown across water?
Fermi #71
  1. 1.If all the gold ever mined were melted into a single cube, how long would one side be?
  2. 2.How many servings of instant noodles were eaten around the world in 2025?
  3. 3.How many people have ever run a mile in under four minutes?
Fermi #70
  1. 1.How many TikToks are uploaded every minute?
  2. 2.How many people live below the Tropic of Capricorn?
  3. 3.How many people visited St. Peter's Basilica in 2024?
Fermi #69
  1. 1.How many different products does a typical Walmart Supercenter stock?
  2. 2.How many police officers work for the New York City Police Department?
  3. 3.A hockey rink's ice is about 1 inch (2.5 cm) thick. How many rinks' worth of ice could you freeze from the water in one Olympic swimming pool?
Fermi #68
  1. 1.How many coffee beans would it take to brew enough coffee to fill a standard 42 gallon (159 L) oil barrel?
  2. 2.What is the average depth of the world's oceans?
  3. 3.We all know that 1 lb of feathers weighs more than 1 lb of bricks, but how many chicken feathers does it take to weigh 1 lb (450 g)?

Showing 7 of 74 puzzles

New to Fermi?

Fermi.gg is a daily estimation game with three numerical questions. Start with a rough guess, break the problem into smaller pieces, and aim to get as close as possible. A new puzzle arrives at midnight New York time.

An independent answer guide. Questions, illustrations and official explanations are credited to Fermi.gg.

Skip to main content