Additionally, the mass–volume relationship of water (as with any fluid) depends on temperature, pressure, purity and isotopic uniformity.

A litre is equal in volume to the millistere, an obsolete non-SI metric unit formerly customarily used for dry measure.

One litre of water has a mass of almost exactly one kilogram when measured at its maximal density, which occurs at about 4 °C.

Modern measurements of Vienna Standard Mean Ocean Water, which is pure distilled water with an isotopic composition representative of the average of the world's oceans, show that it has a density of 0.999975±0.000001 kg/L at its point of maximum density (3.984 °C) under one standard atmosphere (101.325 kPa) of pressure.

[7] There are two international standard symbols for the litre: L and l. In the United States the former is preferred because of the risk that (in some fonts) the letter l and the digit 1 may be confused.

In many English-speaking countries, however, the most common shape of a handwritten Arabic digit 1 is just a vertical stroke; that is, it lacks the upstroke added in many other cultures.

[9] The United States National Institute of Standards and Technology now recommends the use of the uppercase letter L,[10] a practice that is also widely followed in Canada and Australia.

In 1990, the International Committee for Weights and Measures stated that it was too early to choose a single symbol for the litre.

[11] Prior to 1979, the symbol ℓ came into common use in some countries;[citation needed] for example, it was recommended by South African Bureau of Standards publication M33 and Canada in the 1970s.

This symbol can still be encountered occasionally in some English-speaking and European countries like Germany, and its use is ubiquitous in Japan and South Korea.

In 1901, at the 3rd CGPM conference, the litre was redefined as the space occupied by 1 kg of pure water at the temperature of its maximum density (3.98 °C) under a pressure of 1 atm.

The abbreviation "cc" is still commonly used in many fields, including medical dosage and sizing for combustion engine displacement.

For example, in many European countries, the hectolitre is the typical unit for production and export volumes of beverages (milk, beer, soft drinks, wine, etc.)

and for measuring the size of the catch and quotas for fishing boats; decilitres are common in Croatia, Switzerland and Scandinavia and often found in cookbooks, and restaurant and café menus; centilitres indicate the capacity of drinking glasses and of small bottles.

For larger volumes, kilolitres, megalitres, and gigalitres, have been used by the Northern Territory Government for measuring water consumption, reservoir capacities and river flows,[19] although cubic metres are also used.