Convert Paper Weights To Thickness?

I'm trying to sort out paper weights on some Mexico Exporta series stamps.

I found this site(on SCF of course):

http://www.galeon.com/timbresdemexi...ta/index.htm

This site lists the different papers by weight, for instance 65g m2 or 97g m2 etc. I have a decent micrometer.

So a quick internet search led me to this chart:

http://www.paper-paper.com/weight.html

Is it a matter of just measuring the stamps and using the chart?

The reason I ask is that the actual stamp measurements I am making don't seem to match the theoretical measurements from the list/chart. I can think of a bunch of different reasons why (paper composition, thickness change from soaking, gum/no gum etc).

Am I on the right track or totally lost?

Any help greatly appreciated.

Had to buy some more cardboard packaging and my supplier has gone out of business.

Found a great new supplier that cuts up the cardboard cheap as.

My point is that the cardboard I had was 300gm per the thickness but his cardboard was the same thickness but the weight was 260gm.

Paper for US postal stationery (my specialty) was supplied by weight but that weight was for a skid with a set number of sheets. Paper makers would run some thick paper and some thin paper so the proper weight for the skid could be reached. I suspect a similar situation with your stamps. And yes, the ink and the gum will increase the thickness over the paper specification as will humidity.