How to calculate the number of reams in a Metric Ton
Take the sheet size in centimeters (multiply by 2.54 from inches) and calculate the area, divide by 10.000. Multiply by grs. (grams per m2) and by 500 (fixed number of sheets per ream). Divide by 1000 to get weight in kilograms.
Now divide 1000 (1000 Kgs = 1 Metric Ton) by this number and you have the number of reams to a Metric Ton.
For example: size 25 x 38" - 115 grs
25 2.54 x = 63,5
38 2.54 x = 96,5
63.5 x 96.5 cms / 10.000 = 0.6128
0.6128 x 115 35.236 / 1000 = 35.236
1000 / 35.236 = 28,38 reams to a Metric Ton