All Fermi answers
Fermi #23 · Question 1

SpaghettiOs pasta only comes in one letter, O. How many cans would it take to have one pasta piece for every letter O in the entire text of the Lord of the Rings trilogy?

Explore the official answer and the simple reasoning behind this Fermi estimate.

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Answer & explanation

The official answer, with Fermi’s reasoning step by step.

Answer & explanation

Official answer

150

cans

How to estimate it

Fermi’s official “Napkin math”

Lord of the Rings runs about half a million words, and words average around 5 letters, so call it two and a half million letters. How many of those are O? Maybe 1 in 12. A can of SpaghettiOs is packed with little rings, probably around 1,000 of them.

Trilogy word count
~500,000
Letters per word
× 5
2.5M letters, 1 in 12 are O's, ÷ 1,000 per can
≈ 200 cans

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

Source calculation & reference
LOTR trilogy word count (excl. appendices)
≈ 481,000 words
× avg. letters/word, × share of letters that are 'O'
× 4.79 × 7.64%
Total O's needed to spell the text
≈ 176,000
Pasta pieces in a 15.8 oz can (hand count)
÷ 1,180
Cans needed
≈ 150 cans

Reference cited by Fermi: LotrProject word counts for the LOTR trilogy (481,103 words, appendices excluded); Peter Norvig, 'English Letter Frequency Counts: Mayzner Revisited' (Google Books corpus: 4.79 letters/word average, letter 'O' ≈7.64% of all letters); pasta pieces per 15.8 oz can from a hand count of Campbell's SpaghettiOs (≈1,180 pieces), reported by Nerdist and Mashed.

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