I’ve been trying to sort out chain sizes and ratings, and found this site: Notes on Sprockets and Chains. I am now a Chain Geek. For sure, take a look, and you can be one too. Great links at the end, too…
This is specifically what I was looking for:
Chain types are identified by number; ie. a number 40 chain. The rightmost digit is 0 for chain of the standard dimensions; 1 for lightweight chain; and 5 for rollerless bushing chain. The digits to the left indicate the pitch of the chain in eighths of an inch. For example, a number 40 chain would have a pitch of four-eighths of an inch, or 1/2″, and would be of the standard dimensions in width, roller diameter, etc.
The roller diameter is “nearest binary fraction” (32nd of an inch) to 5/8ths of the pitch; pin diameter is half of roller diameter. The width of the chain, for “standard” (0 series) chain, is the nearest binary fraction to 5/8ths of the pitch; for narrow chains (1 series) width is 41% of the pitch. Sprocket thickness is approximately 85-90% of the roller width.
Plate thickness is 1/8th of the pitch, except “extra-heavy” chain, which is designated by the suffix H, and is 1/32″ thicker.