There are countless cigar sizes. Cuba alone produces 69, 2 of which are for handmade Havanas. Each has a factory name, which usually bears no relationship to the name by which we know them, like Prominente (Double Corona), Julieta 2 (Churchill), Mareva (Petit Corona), Franciscano, Carolina, and so on. Some brands, Partagas for example, have 40 sizes, though several are machine-made. This is a throwback to the past when many selections were even larger. More modern brands such as Cohiba and Montecristo have just 11 sizes. Non-Havana brands tend to offer more manageable lines, although many, like Davidoff, which now boasts 19 sizes, have started to grow.
Sadly for the novice, there is no such thing as a standard size or a comprehensive list of sizes. Even the common Petit Corona can be found with different girths, and the name of Churchill covers a variety of alternative, albeit substantial, cigars. Listed below are the 25 most popular Havana sizes under their factory names. This may serve to indicate just how wide a selection is available, but it merely scratches the surface of the full panoply of choice offered by Cuba, let alone the Dominican Republic, Honduras, Mexico, and others.
The girth of a cigar is customarily expressed in terms of its ring gauge in 1/64th's of an inch. Thus, if a cigar has a ring gauge of 49, it is 49/64ths of an inch thick. Similarly, if a cigar had a ring gauge of 64, it would be an inch thick. Only a couple of cigars come into this size today, the 9-inch long Royal Jamaica Goliath, and the same length Jose Benito Magnum from the Dominican Republic. The Casa Blanca Jeroboam and Half Jeroboam come with a whopping 66 ring gauge.
The largest properly smokable cigar made was Koh-i-Noor, made before World War II by Henry Clay for a maharaja. The same size, called the Visible Inmenso (18 inches long, 47 ring gauge) was made for King Farouk of Egypt. There was also once a panatela measuring 19 1/2 inches. At the Partagas factory in Havana, they keep a collector's item: a cigar measuring almost 50 inches. You can also see a cigar a yard long with a ring gauge of 96 kept at the Davidoff store in London.
The smallest regularly made cigar was the Bolivar Delgado, measuring under 1 1/2 inches.
There are plenty of variations to be found within a particular brand, particularly if the choice is large. Different brands, on the whole, tend to be expert at making different sizes. So, while the large ring gauge cigars in a certain brand might be excellent, you shouldn't assume that the smaller ones will either taste similar or be as well made. It comes down to actually trying the cigars.