Convert knots to kilometers per hour

The formula

kilometers per hour = knots × 1.852

knots to kilometers per hour — quick reference

One knot is one minute of latitude an hour, which is the whole point of the unit

The nautical mile is defined as exactly 1,852 m because that is close to one minute of arc of latitude. Sixty of them make a degree, so distance on a nautical chart can be measured straight against the latitude scale printed up the side - dividers on the chart, dividers on the margin, no scale bar and no conversion.

The name is older than the definition. Speed was measured by paying a knotted line out over the stern behind a floating log and counting the knots that ran through the hand while a sand glass emptied. The count was the speed, which is why a vessel makes ten knots and never ten knots per hour.

Storm thresholds look arbitrary in km/h because they were set in knots

Multiplying knots by two and taking off seven per cent gives km/h closely enough: 20 knots becomes 40 less 2.8, or 37.2, against a true 37.04. The anchors worth keeping are 10 knots at 18.5 km/h, 20 at 37, and an airliner’s 500-knot cruise at 926 km/h.

Meteorology explains the odd numbers. A gale is Beaufort force 8, 34 to 40 knots, which converts to 63-74 km/h; hurricane force begins at 64 knots, or 118 km/h. Those uneven thresholds in a metric forecast are not arbitrary at all - they are round knot figures that have been converted.

Questions