The modius , although normally a dry measure, was commonly used to record the volume of amphoras in the Western Empire. It is roughly equivalent to two imperial gallons. The graffiti and dipinti referred to above often record the volume of the amphora in modii and a smaller unit, the sextarius - approximately a pint. The Latin word amphora is also a unit of volume, used to describe the capacity of shipping. In the Eastern Empire the system is complicated by the use of local systems of measures.
Some amphoras seem to be multiples of the choe , equivalent to the Roman congius .
The bibliography of amphora studies is extensive. The earlier studies by Callender 1965 and Beltr n Lloris 1970 remain valuable. Reports from the Ancient Monuments Laboratory in London by D. F. Williams and others contain interim assessments of important collections of amphoras from sites in Britain, prior to the publication of the final site reports. The track of amphora studies through the 1970s and 1980s can be followed through a series of conference proceedings, published in the Collection de l' cole Fran aise de Rome and elsewhere as Baldacci et al. Rothschild-Boros 1981 .