Kitchen Subfloor Thickness
Plywood comes in a bewildering variety of sizes. I build a lot of cabinets, and I have encountered nominal 3/4 inch plywood that is 23/32, 3/4, and metric. As a result, I have a collection of router bits sized to fit the plywood.
If you go to a real lumber store, not a big box store, they may very well have actual 1/2 inch underlayment and actual 3/4 inch plywood. They probably also have plywood that is short of the dimensions you want. Bring a good tape or a measuring gage to be sure.