unit:MI

The exact length of the land mile varied slightly among English-speaking countries until the international yard and pound agreement in 1959 established the yard as exactly 0.9144 metres, giving a mile of exactly 1,609.344 metres. The United States adopted this international mile for most purposes, but retained the pre-1959 mile for some land-survey data, terming it the US survey mile. In the US, statute mile formally refers to the survey mile, about 3.219 mm (1/8 inch) longer than the international mile (the international mile is exactly 0.0002% less than the US survey mile).