The amphora, or amphora quadrantal was a unit for measuring liquids or bulk goods in the Roman Empire, and for estimating the size of ships and the production of vineyards.
The volume of a standard amphora is equal to one cubic foot.
Thus the Roman amphora (one foot ~29.6 cm) contains about 26 litres, Greek amphoras varied from 18.5 L (pous italikos ~26.5 cm) to about 36 L (pous Ptolemaikos ~33.1 cm). The French amphora, also called the minot de Paris, is 1/8 muid or one cubic pied du roi and therefore about 34 litres.
Along with other standard measures and the Roman currency, it gave an added advantage to Roman commerce. A standard amphora, the amphora capitolina, was kept in the temple of Jupiter on the Capitoline Hill in Rome.