Originally Posted by DaveSSS

Others will suggest the big/big method, skipping the RD and adding 1 inch to the length when the ends are brought together. Tha works too, but can give ambiguous results when the end that come together can't be joined. Then you add 3 links or 1-1/2 inches. It also suggests the shortest length unless the casset you're using has the largest cog size the RD can handle.

I read lots of post where someone used the big/big method and needs to lengthen a chain when they want to switch from a 12-23 to a 12-27. The little/little method avoids that problem.