All you wanted to know about bottle sizes, but were afraid to ask.
Split
187 ml
Half-Bottle
Holds 375 ml or one half of the standard bottle size.
Bottle
Holds 750 ml – the standard size.
Magnum
Two bottles or 1.5 litres.
Double Magnum
Twice the size of a magnum, holding 3.0 litres, or the equivalent of 4 bottles.
Jeroboam
There are two sizes of Jeroboams: the sparkling wine Jeroboam holds 4 bottles, or 3.0 litres: the still wine Jeroboam holds 6 regular bottles, or 4.5 litres.
Rehoboam
Champagne only – 4.5 litres or 6 bottles.
Imperial
Holds 6 litres or the equivalent of 8 bottles. Tends to be Bordeaux shaped.
Methuselah
Same size as an Imperial (6 litres) but is usually used for sparkling wines and is Burgundy-shaped.
Salmanazar
Holds 12 regular bottles (one case), or 9.0 litres.
Balthazar
Holds 16 bottles or 12.0 litres.
Nebuchadnezzar
Holds 20 bottles of wine or 15.0 litres. According to my colleague John Ager, quoting from Fogwells Wine Guide, it is equivalent to 20 standard bottles (15 litres, 3.96 US gal., 3.3 UK gal.). Bill Tighe says that the Nebuchadnezzar, according to the “Random House unabridged Dictionary of the English language, as she is spoken here in the colonies, is 20 quarts, or 18.9 litres”. I suspect something amiss here! The Concise Oxford doesn’t mention the word. The Encarta World English Dictionary refers only to the Babylonian king.