1 degree of latitude is 111 kilometers, or about 69 statue miles or 60 nautical miles. 1 degree of longitude varies based upon latitude; at the equator, it is also about 111 kilometers, but decreases to about 55.5 kilometers at 60°N/S. The exact conversion is 111km times the cosine of the latitude.

A nautical mile is the distance in one minute of latitude. Recall that latitude is measured in degrees/minutes/seconds. Thus, since there are 60 minutes in 1 degree of latitude, there is a nearly direct conversion between nautical miles and latitude. It is equal to 1.15 times the length of a statute mile, which is the normal mile we refer to in speed and driving discussions. One nautical mile is 1.85km in length; one statute mile is 1.61km in length.

Usually, measurements of the storm's position accuracy and eyewall diameter are given in nautical miles, whereas most distances -- especially in public advisories -- are given in statute miles.