In Ancient Roman measurement, the acetabulum was a measure of volume (fluid and dry) equivalent to the Greek ὀξύβαφον (oxybaphon). It was one-fourth of the hemina and therefore one-eighth of the sextarius. It contained the weight in water of fifteen Attic drachmae.

Used with some frequency by Pliny the Elder, in a 1952 translation the unit was judged to be equivalent to 63 ml (2.2 imp fl oz; 2.1 US fl oz).^[1] However, other sources estimate a higher value of perhaps 68 ml (2.4 imp fl oz; 2.3 US fl oz) (see Ancient Roman units of measurement).

•  This article incorporates text from a publication now in the public domain: Smith, William, ed. (1870). "Acetabulum". Dictionary of Greek and Roman Antiquities. London: John Murray.