We've put together an easy-to-use roller chain size charts for all ANSI standard size chains. There are 4 charts listed below that cover single, double, triple & quadruple row ANSI roller chain dimensions.
The 3 most important dimensions to measure first is the chain Pitch (P), Roller Diameter (d1) & Inner Width (b1). After this, you can compare the remaining dimensions to verify the chain size you may have.
If the dimensions are not matching, then its likely that you have a Heavy Duty Roller Chain, Metric Roller Chain or a Non-Standard Roller Chain.
* Rollerless chain. d1 = Bushing diameter