I've tried searching for it but while there are a lot of hits on the fact that graphene's conductivity is high, there seem to be very few on how the conductivity is actually measured. Would you use the same method as you do with metal wires? Using cross sectional area, length, an ohmmeter and calculating the resistivity from that? Graphene doesn't have a cross sectional area, does it? How would one go about measuring its conductivity?