Same situation for me with the length.I have the opposite problem. I normally take a waist size of 32, but that only proves a 32 inch inseam when I need at least a 33. So I end up sizing up to a 33 to get a workable inseam...although past chinos have shrunk on me becoming too short.
The shrinking is a real pain in the ass. I end up having to replace chinos that are otherwise perfectly wearable because the length ends up 1-2 inches shorter than new.