In the 17th century, mariners measured vessel speed using a wooden pie slice called a chip log attached to a line with knots tied regularly every 47 feet and 3 inches (14.4 m).

When thrown overboard, a sailor counted how many knotted points passed through their fingers in exactly 28 seconds using a sandglass. The number of knots counted directly equaled the speed in nautical miles per hour!

By international agreement since 1929, one international nautical mile is defined as exactly 1,852 metres (around 6,076 feet).

• 1 knot = exactly 1.852 km/h
• 1 knot = ~1.15078 statute mph
• 1 knot = ~0.51444 metres per second
• 1 knot = ~1.68781 feet per second