The stadion, formerly also anglicized as stade, was an ancient Greek unit of length, based on the circumference of a typical sports stadium of the time. According to Herodotus, one stadion was equal to 600 Greek feet. However, the length of the foot varied in different parts of the Greek world, and the length of the stadion has been the subject of argument and hypothesis for hundreds of years. Various hypothetical equivalent lengths have been proposed, and some have been named. Among them are:
An empirical determination of the length of the stadion was made by Lev Vasilevich Firsov, who compared 81 distances given by Eratosthenes and Strabo with the straight-line distances measured by modern methods, and averaged the results. He obtained a result of about.
Which measure of the stadion is used can affect the interpretation of ancient texts. For example, the error in the calculation of the Earth's circumference by Eratosthenes or Posidonius is dependent on which stadion is chosen to be appropriate.
During the Middle Ages and the modern period, the word stadium has been used as a synonym for the furlong, which is of Anglo-Saxon origin.