RING GAUGE
A cigar is measured by length and ring gauge (diameter). The length
is measured in inches. The ring gauge is measured in units of 1/64th of
an inch. A 64-ring cigar would be one inch in diameter.
Most cigars are between 32 and 52-ring size. For example, a cigar
that is called “8 x 48″ is 8 inches long and 48/64ths of an inch in
diameter.
The girth, or thickness- determines how much of the cigar’s burning
tip is exposed to air. The fatter the cigar, the slower and cooler a
cigar smokes because more of the filler is exposed to air.
-source, various via Internet.