12" will work fine. My manual says 1" greater, but I ignore that rule all the time. My big Le Creuset hangs over quite a bit since it's oval. My moka pot is tiny and it works fine too. If you want to use something gigantic like a griddle, then buy one with a bridging element

With induction, an electro-magnetic field transfers energy into the pan base. The base heats and that heat is conducted to the rest of the pan and its contents.

kas

The reason for the "maximum" rings is to keep pans from extending into areas where the cook-top glass may be over less heat resistant electronics. The hob heats the pan, then the pan heats the glass.

There are two conditions that can ameliorate this limitation.

First, most pans are larger in diameter than their bases, so an 11-inch base is likely to be associated with a 13-inch or larger pan.

Second, if thin silicone pads are used to "air-gap" the pan base from the glass, the field lines will still interact normally with the pan base, but only radiant heating from the pan to the glass will occur, and not conductive heating (except a reduced amount through the pads). This keeps the glass cooler so any danger with being over-sized is reduced.

kas

Kaseki is quite right about the differences in the diameter of the base and the top of pots. So measure yours to see what size pans you have.

Also consider how you cook. We decided on a 36" cooktop so we could have two larger hobs because we often use one large pot for pasta and a large skillet for making sauce. But if that's not your cooking style, then you won't miss the second larger hob.

As Kaseki also notes, there are ways around the issue if you do occasionally need to use a large pot on a smaller hob.

The reverse situation is a very nice feature of induction: using a smaller pot on a larger hob. As long as the pan is recognized (so that the hob will operate), only the pan surface space gets warm/hot. The rest of the hob remains cool.

My 30" KA induction cooktop has the same hob sizes as you are describing. I can put my 12 qt pot or my 12" skillet on the big hob while an 8 qt pot or a 10" skillet is on a 7" hob. No problem. I use big pots on there all the time. You are going to love your new induction cooktop.