By: Elizabeth Nix

Why is a ship’s speed measured in knots?

Ships, Naval History
Published: May 14, 2014Last Updated: May 27, 2025

Ancient mariners used to gauge how fast their ship was moving by throwing a piece of wood or other floatable object over the vessel’s bow then counting the amount of time that elapsed before its stern passed the object. This method was known as a Dutchman’s log. By the late 16th century, sailors had begun using a chip log to measure speed. In this method, knots were tied at uniform intervals in a length of rope and then one end of the rope, with a pie-slice-shape piece of wood (or “chip”) attached to it, was tossed behind the ship. As the vessel moved forward, the line of rope was allowed to roll out freely for a specific amount of time, which was typically tabulated with an hourglass. Afterward, the number of knots that had gone over the ship’s stern was counted and used in calculating the vessel’s speed. A knot came to mean one nautical mile per hour. Therefore, a ship traveling at 15 knots could go 15 nautical miles per hour.

For a number of years, there was disagreement among various nations about the exact measurement of a nautical mile, which is based on the Earth’s circumference. In 1929, the international nautical mile was standardized at 6,076 feet; it was adopted by the United States in 1954. A nautical mile is different from a mile on land, which is based on walking distance. The Romans first defined a land mile as 1,000 paces or pairs of steps; it was set at its current measurement of 5,280 feet by Queen Elizabeth I in 1593.

Related Articles

Self-Propelled Road Machine, 1868

When Zadock Dederick unveiled a mechanical man, the press called him a 'new Frankenstein.'

Art made of code named Kryptos sits on the grounds of the C.I.A. Headquarters in Virginia

Since 1990, the world's top codebreakers have been stumped by a mysterious sculpture called 'Kryptos.'

Marie Sklodowka Curie (1867 - 1934) in her laboratory. She shared a Nobel Prize in Physics in 1903 with her husband Pierre for their work in radioactivity. In 1911 she became one of the few people to be awarded a second Nobel Prize, this time in chemisty for her discovery of poloium and radium. Her daugther and son-in-law also shared a Nobel Prize for Chemistry in 1935 for work in radioactive materials. He went on to become the first chairman of the French atomic energy commission. France.

Marie Curie won not just one Nobel Prize in her lifetime, but two, for her groundbreaking work in radioactivity.

About the author

Fact Check

We strive for accuracy and fairness. But if you see something that doesn't look right, click here to contact us! HISTORY reviews and updates its content regularly to ensure it is complete and accurate.

Citation Information

Article title
Why is a ship’s speed measured in knots?
Website Name
History
Date Accessed
August 27, 2025
Publisher
A&E Television Networks
Last Updated
May 27, 2025
Original Published Date
May 14, 2014

History Revealed

Sign up for Inside History

Get fascinating history stories twice a week that connect the past with today’s world, plus an in-depth exploration every Friday.

By submitting your information, you agree to receive emails from HISTORY and A+E Global Media. You can opt out at any time. You must be 16 years or older and a resident of the United States.More details: Privacy Policy | Terms of Use | Contact Us
King Tut's gold mask