The knot is the term for speed used by the aviation and shipping industries. Sometimes abbreviated as KTS, the knot is measured in nautical miles per hour, and should not be confused with speeds given in miles per hour. The nautical mile differs from the statute or conventional mile by approximately 796 feet. The nautical mile, or one arc minute, is based on the circumference of the earth divided into degrees and minutes. Distances and speeds described using the nautical mile are more relevant to map-reading than distances and speeds that utilize the conventional mile.
Multiply the wind speed given in knots or KTS by 1.15 to obtain the equivalent speed in miles per hour (MPH). For example, a wind speed of 6.0 KTS is equivalent to a wind speed of 6.0 x 1.15 = 6.9 MPH.
Divide the wind speed given in MPH by 1.15 to obtain the equivalent speed in KTS. For example, a wind speed of 10.0 MPH is equivalent to a wind speed of 10.0/1.15 = 8.7 KTS.
Compare wind speeds with the same units. For example, a wind speed of 6.5 MPH is slower than a wind speed of 6 knots, because 6.5 MPH is equivalent to 6.5/1.15 = 5.7 KTS, which is less than 6 knots.