Our counter is very long so I don't think I can help with your specific question. However, I just wanted to point out that just as importantly if there is a wall next to one side of the vanity try to leave enough elbow space there as well. My daughter & her husband don't use their second sink because there is only a 4-6 inch gap in between the wall and the sink so it's very limiting on how you can move around.

That is part of my problem with the design layout. The left side will be against a wall and I would like to have at least 24" to the center of the sink. Actually, I would prefer 27". The right side shouldn't be a problem but I would like to keep it fairly even from right to left, which is why I'm stuck on 12" between sinks at the moment. The counter can be as long as 84" but I'd rather have it shorter to give me a larger linen closet.

Mileaday, I can empathize with you because I have an 84.5" long vanity space with double sinks, except mine is between TWO walls. I wanted to replace my existing partial-overlay cabinets with the same sizes, i.e. 30" + 24" + 30" but I wasn't sure full overlay would have enough room. I also wanted more elbow room between the two sinks, as well as on each side next to the wall. I decided to use a 21" drawer base between two 30" sink bases with 3.5" of space for fillers to be split on each end. Each sink measures 17" x 14" so I will have 36" between the two sinks! With a 1 3/4" filler on the wall side of each sink base, it leaves 8 3/4" from the edge of the sink to the wall. Hope this helps! Goldie

I have a similar layout to Goldie's. There's 9" of space between the edge of my sink and the side splash, and it gives me plenty of elbow room.