Normal cabinet depths are:

Lower/Base: 24"
Upper/Wall: 12"
Countertop overhang: 1-1/4"

However, 15" deep upper cabinets are becoming more common. If you have 12" diameter dinner plates, I recommend getting 15" deep upper cabinets so the plates will fit easily (assuming you put your plates in upper cabinets!)

If you can afford it, 30" base and 18" uppers would give you quite a bit more room...but it may be more difficult to reach the back of the upper cabinets, even the middle shelves. If you're tall, though, it may not be as big an issue.

30" deep base cabinets have the added benefit of 6 extra inches of working counter depth....something I would have loved to have but couldn't fit if I wanted to keep my peninsula!

30" deep base cabinets can be expensive. Some people who really just want the added counterspace stick w/24" base cabinets, pull them out 6" from the back wall, and install a 6" deeper countertop.

HTHT!

Thanks buehl. Yes, I think I would want 15" uppers. I am short so 18" would not work as you said. I will price out 24" vs 30" base cabinets. Fortunately, I would have enough space between the aisles.

I think you'll find that it's difficult to price out 30" base cabinets unless you're going with a local custom builder.
Most cabinet companies will only do 24" with the 6" pullout. If you really need the storage space, then you probably want to use the space rather than have a 6" void.
I did find a couple of places that said they could custom make the 30" deep bases, but that they could only get short (23" approx) blumotion slides, which made the depth irrelevant to us because virtually EVERY base cabinet in our kitchen is a pullout or drawer.
Scherr's gave us 27" long blumotion slides for our 30" base cabinets, which means we end up with 25% more storage than the 24" deep standard bases. And that means that I can store an entire 12-place setting set of dishes in one drawer - cups, saucers, big dishes, little dishes, rimmed bowls, and unrimmed bowls.
So, to do it right, you'll probably need to check with a local custom cabinet builder who can locate the longer slides. Don't believe them if they say they don't exist, because they do. And then put the double oven at whatever height works for you (instead of reaching up over a hot oven door, you can reach straight to it). And make tray dividers that fit entire full-sheet cake pans. Okay, off my soapbox now.
Lisa

Lisa, if you have 27" blumotion glides for 30" deep drawers, are they full extension?
Thanks

But keep in mind the shape of your kitchen. For example, in our penultimate kitchen we had 32" deep lowers and 16" deep uppers but it was essentially an enormous galley kitchen (~9' between the runs of cabinets). It worked.

In our current kitchen, which is u-shaped, cupboards deeper than 24" most likely would not have worked. At the least, we would have had to lose the island and, due to the two 90 degree corners (of the u-shape), the deeper cupboards would have shrunk up that space even more.

I'm not sure I'm wording this well, but what's "ideal" (and I definitely think those 30" deep lowers are ideal!) and what's realistic / practical are sometimes diametrically opposed ....

If you can get away with 30" -- lucky you! But if you can't, keep that in mind and maybe make your drawers wider (or pull-outs, if you're not having drawers) to increase your storage capacity.

Good luck!

I have a mix of 27" deep lower cabinets and 24" deep. The sink is inset a bit on the corner to make this work well on the 27" side. The uppers are all 15" deep. After two years with my cupboard doors partly open because of the new dishes...this was my first wish!