How many pages does Leonardo's Codex Leicester contain?

How many pages does Leonardo’s Codex Leicester contain? 72 pages.

The Codex Leicester is a 72-page collection of scientific notes and drawings by Leonardo da Vinci. Its physical structure explains the number: it consists of 18 sheets of paper, each folded in half and written on both sides, producing four pages per sheet.

Leonardo assembled much of the material between about 1504 and 1508, though the notes reflect observations and ideas developed over time. The subjects include water movement, rivers, whirlpools, geology, fossils, atmospheric effects, astronomy, and the nature of moonlight. His diagrams show how closely he connected drawing with investigation.

The manuscript is not a conventional linear book. Leonardo wrote in Italian using his characteristic mirror script, generally from right to left, and filled the pages with interlinked observations, sketches, and speculative explanations. This is why “72 pages” is more precise than counting only the 18 physical sheets.

The codex was once known as the Codex Hammer after industrialist Armand Hammer. In 1994, it was purchased by Bill Gates, who has supported exhibitions and digital presentations of the manuscript.