yes
Curves should be factored in but the norm is to just measure from the top base to the tip.
It does make a difference though. Think of measuring the inside rim of a tire compared to the outside circumference.

I curve upwards and have a 1.5 inch difference. Shy of 8 from the top, and 9.5 along the bottom although it's harder to decide where the base is from the bottom.

condoms even bunch up a bit for me on the topside