Knots to Feet Per Second (kn to ft/s)

1 knot equals 1.687809857 feet per second (rounded).

How to convert knots to feet per second

To convert knots to feet per second, multiply the number of knots by 1.687809857. The factor is rounded to 10 significant digits. To go the other way, multiply feet per second by 0.5924838013 (rounded).

feet per second = knots × 1.687809857

Example: 10 knots = 16.87809857 feet per second.

About these units

Knot (kn)

NauticalCurrent unit

One nautical mile per hour, exactly 1.852 km/h. The unit of speed for ships, aircraft and wind.

Knots in a rope really were counted. Before the mid-nineteenth century, sailors threw a weighted wooden board, the chip, off the stern on a line called the log-line. The line carried knots at regular intervals, and a sailor counted how many passed through his fingers while another timed the run with a sandglass. William Bourne's A Regiment for the Sea, printed in 1574, is the first known description, and many ships spaced knots 8 fathoms, about 14.6 meters, apart with a glass of roughly half a minute.

Today a knot is one nautical mile per hour, exactly 1,852 meters per hour, about 1.151 mph or 0.514 m/s. A ship making 1 knot along a meridian covers about one minute of latitude per hour, which is why charts and the unit fit together. It is not an SI unit, and the symbol is kn, though kt is common in aviation. Saying knots per hour is wrong, since that would describe acceleration. The US moved civil aircraft standards to nautical miles and knots in 1969, and winds and currents are also quoted in them.

1 knot = 0.5144444444 meters per second (approximately).

Sources: Wikipedia: Knot (unit); Wikipedia: Chip log; NIST Guide to the SI, Appendix B.8: conversion factors

Foot Per Second (ft/s)

US & ImperialCurrent unit

Exactly 0.3048 m/s. Used for velocity in US engineering, ballistics and fluid flow.

Compound units rarely have a recorded inventor, and the foot per second is a plain example: it is just a foot divided by a second. The foot underneath it began as a body-based length ranging historically from about 250 to 335 millimeters, with ancient Greek and Roman feet near 300 mm. Before the SI arrived in 1960, feet per second, miles per hour and knots were more common than meters per second, depending on region.

The 1959 international agreement fixed the foot at exactly 0.3048 meter, so one foot per second is exactly 0.3048 m/s, about 1.097 km/h or 0.6818 mph. Sound moves at about 1,125 ft/s in dry air at 20 °C, which is 343 m/s. Chuck Yeager's Bell X-1 reached about 361 m/s in 1947, near 1,184 ft/s. The unit remains common in American engineering and science, where lengths are still given in feet and inches.

1 foot per second = 0.3048 meters per second (exactly).

Sources: Wikipedia: Foot per second; Wikipedia: Foot (unit); NIST Guide to the SI, Appendix B.8: conversion factors

Related conversions

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