Liquid dimensions

The "metric system", which was adopted by 17 countries in 1875 by signing a treaty, is the basis for all hollow measures used worldwide today (Table 1). In addition, very old gauges are still in use (Table 2). The Anglo-American measurement systems are almost only used in the USA, England and some other countries (Table 3). The ancient Roman gauges are included under the term congius.

Metric system

Only the USA, Myanmar and Liberia have not yet adopted the metric system, although it is used in practice by the latter two. One litre of water weighs exactly one kilogram (kg) and has a volume of 1 dm³ at a temperature of 3.98 °C and an air pressure of 1013.25 hPa (hectopascal).

Different measures

In the past, a distinction was made between measures for liquids (liquid measures) and measures for solids (dry measures for nuts, salt, flour and grain). In some cases, dry measures were further differentiated into those for "smooth fruit" (e.g. hulled grain) and those with "rough fruit" (after threshing, not hulled). In the sources on old units of measurement, the information on volumes often varies and the differences are sometimes quite considerable.

The picture shows six hollow measures from the "Mens ponderia" in Pompeii, a municipal institution for controlling weights and measures. These were found during excavations in the city destroyed by the eruption of Vesuvius in 79 AD.