Knots. ... One knot equals one nautical mile per hour, or roughly 1.15 statute mph. The term knot dates from the 17th century, when sailors measured the speed of their ship using a device called a “common log.” The common log was a rope with knots at regular intervals, attached to a piece of wood shaped like a slice of pie ...

Why do we use knots instead of mph?

By the late 16th century, sailors had begun using a chip log to measure speed. ... 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.

Do pilots use knots or mph?

The unit of speed 'knots' has been the standard unit of speed in aviation since its beginning. One knot (1kt) is equal to one nautical mile per hour (1Nm/h) and it has been defined to be equal to 1.852km/h in terms of SI units.