I haven't purchased RCD jeans from Massdrop, but I did recently purchase a pair direct.
I'm 5'11" 165lb, and generally wear a 31 or 32 waist in most brands. I ordered the RCD jeans in 32, and they fit well. I would say the 32 size wears closer to a 31 than a 33, so if in doubt maybe go up a size. The jeans feel tight at first, especially in a knees, but after a few days of wearing around the house they loosen up. I haven't washed them yet, and I'm hoping they don't shrink when I do.
devaThere isn't much variation in my experience. I'm a 32 in J.Crew Chinos, and a 31 in their shorts. All other brands I have tried, I am also a 31 or 32. I don't own a single pair of pants or shorts that are not 31 or 32. Lucky Brand, Levis, Carhartt, Ex Officio, Dockers, etc, etc.
I'm 5'11" 165lb, and generally wear a 31 or 32 waist in most brands. I ordered the RCD jeans in 32, and they fit well. I would say the 32 size wears closer to a 31 than a 33, so if in doubt maybe go up a size. The jeans feel tight at first, especially in a knees, but after a few days of wearing around the house they loosen up. I haven't washed them yet, and I'm hoping they don't shrink when I do.