The unit described on this page was in use prior to modern methods of precision measurement. It was based on a standard which is no longer available, and which is not capable of being calibrated against modern measurement units. Therefore, the equivalence to modern SI units or to current United States customary units can only be considered approximate.
Ancient Greece consisted of a number of city-states, each with its own set of measurement standards. The most important of these city-states, Athens, eventially came to have dominion over much of the area, so that the Attic Greek units of length or distance (as well as their units of measurement for other quantities) became standard for a large region, and this page tabulates those Attic Greek units.
Although the Greek units of measuring lengths and distances were well-defined and their relationships to each other are well known, no actual Ancient Greek (Attic or other) standards are definitively known by the present day, so that the only way of determining the length of any Attic Greek unit would be to measure something in modern terms whose length was given by the Greeks in their units. And because this procedure does not give us any clue to which unit may have been the base unit and which were subsidiary units, this distinction really does not apply to the Attic Greek units here given, so all the units really have equal status. However, such measurements have been made, and they indicate (though requiring statistical treatment to allow for the inaccuracies of the Greeks' own measurements) that the best estimate of the Attic Greek pous (foot) can be taken as 0.30856 m = 1.0123 ft = 0.3374 yd, and this distance will be adopted on this wiki as the basis for interpreting all other Attic Greek units of length or distance, as their relation to the mile is known.