I assume GCE is based on a space-shared design (1:1 pinned vCPUs); if that's not correct then this becomes harder. On https://developers.google.com/compute/docs/instances#overvie... I see the term "Virtual Cores", but I don't want to hear about virtual cores. I want to know how many physical cores are backing the VM. (I don't find the term "logical core" further down the page helpful either.)

So I would say:

n1-standard-1: 1/2 physical core

n1-standard-2: 1 physical core

...

n1-standard-8: 4 physical cores