Ikea rail height

Afternoon,

Got some ikea metod wall cabinets to fit in my existing kitchen. They're the 80cm tall ones. No where can I find what height the rail needs to be on the wall. I just wondered if there was a basic height?

I understand it personal preference as they could be at any height, but i also can't find how high above the rail the cabinets will sit.

Any ideas guys?

Thanks in advance