The metric system is universally used in Italy. With the notable exception of the internationally adopted miglio marino/nautico (nautical mile) and the nodo (knot = 1 nautical mile an hour), the existence of Italian translations for most imperial (or American) terms (such as pòllice for “inch”) does not necessarily entail knowledge of the corresponding value by the native Italian speaker. In order to avoid confusion, it is therefore advisable, when translating imperial or American measurements from English, to turn them into or give an indication of their metric equivalents. The following tables of conversion include both precise and rounded-up values. While the first set might of course be necessary in some circumstances (e.g. in the fields of science and technology), in most everyday situations the approximate equivalences will be quite adequate. A measurement of “4 in.” will therefore be translated into (circa) 10 centimetri (rather than 10,156 centimetri), and so on.

All words ending in -grammo are stressed on the second-last syllable (e.g. centigràmmo), whereas all the words with -metro and -litro are stressed on the third-last syllable (e.g. centìmetro, centìlitro), although it is not uncommon to hear millilìtro instead of millìlitro. Note that the prefix kilo- is often spelt chilo- in Italian, even though the letter κ is regularly used in the abbreviations.