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 #643 questions

A little help for today’s big questions.

1QUESTION 1 OF 3

How many times does the name "Harry" appear across all seven Harry Potter books?

Reveal answer & explanation

Official answer

16,557

times

How to estimate it

Fermi’s official “Napkin math”

Seven books, maybe 500 pages each. How often does Harry's name show up on a page? He's in almost every scene, so maybe 5 times.

Books
7
Pages per book
× 500
Harry per page
× 5
7 × 500 × 5
≈ 17,500

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

Source calculation & reference
Word 'harry' across all seven books (tidytext word count)
16,557
Most in Order of the Phoenix
3,730
Least in Philosopher's Stone
1,213
Series total
16,557

Reference cited by Fermi: UC Business Analytics R Programming Guide (University of Cincinnati), word-frequency analysis of the full text of all seven books: 'harry' appears 16,557 times

Full answer & compare your estimate
2QUESTION 2 OF 3

What is the combined age of all of the ambassadors to the United Nations?

UN General Assembly Hall

UN General Assembly Hall

The empty United Nations General Assembly Hall in New York, rows of green desks facing the gold wall behind the podium.

Illustration from Fermi.gg

Reveal answer & explanation

Official answer

11,800

years

How to estimate it

Fermi’s official “Napkin math”

There's one ambassador for each of the 193 member countries. How old is a typical one? They're senior diplomats well into long careers, so mid fifties. Call it 55.

UN ambassadors
193
Typical age
~55
~200 × 55
≈ 11,000

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

Source calculation & reference
Current UN ambassadors with a published birth date (58 of 193)
average age ≈ 61
One ambassador per member country
× 193
193 × 61
≈ 11,800

Reference cited by Fermi: UN Protocol list of permanent representatives in New York (as listed on Wikipedia, December 2025), with birth dates from Wikidata for the 58 who have one: average age 61

Full answer & compare your estimate
3QUESTION 3 OF 3

If everyone on Earth formed one giant human pyramid, with each row one person shorter than the row below, how many rows tall would it be?

4 rows, 10 people

4 rows, 10 people

Ten friends in swimsuits forming a four-row human pyramid on a sunny beach.

Illustration from Fermi.gg

Reveal answer & explanation

Official answer

129,000

rows

How to estimate it

Fermi’s official “Napkin math”

Try a round guess: 100,000 rows. The bottom row has 100,000 people and the top has 1, so the average row is about 50,000. How many is that? 100,000 × 50,000 is 5 billion, not enough, so try a bit taller.

Guess 100,000 rows, average row 50,000
≈ 5 billion, too few
Try 120,000 rows, average row 60,000
≈ 7.2 billion, close
A little taller still
≈ 125,000 rows

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

Source calculation & reference
World population, mid-2026 (UN World Population Prospects 2024)
≈ 8,300,700,000
Rows 1 + 2 + 3 + ... + n = n(n+1) ÷ 2
n(n+1) ≈ 16,601,000,000
Solve for n
≈ 128,800 full rows
≈
129,000

Reference cited by Fermi: United Nations World Population Prospects 2024, mid-2026 world population estimate

Full answer & compare your estimate

Fermi answer archive

Find a past question and explore the reasoning behind it.

Fermi #63
  1. 1.How many drives would it take Tiger Woods to golf the length of Central Park?
  2. 2.How much fuel does a Boeing 747 burn per hour at cruising altitude?
  3. 3.How much did the world spend on movie tickets in 2025?
Fermi #62
  1. 1.How many kiwifruit would it take to weigh as much as an adult North Island brown kiwi?
  2. 2.How many cigarettes are smoked worldwide every day?
  3. 3.How many people live north of the Arctic Circle?
Fermi #61
  1. 1.How many sprays does it take to empty a bottle of Chanel No. 5?
  2. 2.How far is the world record for the longest paper airplane throw?
  3. 3.How much did the 20 Premier League clubs pay in player wages in the 2024/25 season?
Fermi #60
  1. 1.How many words are in the Bee Movie script?
  2. 2.How many people worldwide live within 10 km (6.2 miles) of an ocean coast?
  3. 3.Czechs drink more beer per person than anyone else in the world. How much beer does the average Czech drink in a year?
Fermi #59
  1. 1.How many crew members work aboard Icon of the Seas, the largest cruise ship in the world?
  2. 2.How many chicken eggs are laid worldwide every day?
  3. 3.How many plates of sushi are eaten at conveyor-belt sushi restaurants in Japan each day?
Fermi #58
  1. 1.How far is it from the Statue of Liberty in New York to Christ the Redeemer in Rio de Janeiro?
  2. 2.How many hotel rooms are there in London?
  3. 3.How many wooden blocks come in a new game of classic Jenga?
Fermi #57
  1. 1.How many different people have been aboard the International Space Station?
  2. 2.Wang is the most common surname on Earth. How many Wangs are there?
  3. 3.How many people graduated from a computer and information sciences program in Canada last year?

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