The weight of metric paper is given in grams per square meter (gms). By definition, one square meter is one A0 size sheet or 16 A4 size sheets. The weight of United States letter size paper is given in pounds per 500 sheet ream of uncut C size paper. For the letter size paper, a sheet is cut into 4 pages so that a cut ream of letter size paper, 500 letter size sheets, weighs 5 pounds if the paper is nominally 20 pound paper. Note that each type of paper has a different "base size," so 200 gsm of one paper will give a differnt Lbs/ream equivalent for a different paper. For instance: 20 lbs of Bond is almost the same as 28 of cover.

 

Weight
in
Pounds
Bond
Dual Purpose
Duplicator
Ledger
Safety
Writing
Cover Bristol  Index Offset
Text
Book
Basis size (inches)
17.0x22.0 20.0x26.0 22.5x28.5 25.5x30.5 25.0x38.0
20 75.3 gsm 54.1 gsm 43.9 gsm 36.2 gsm 29.6 gsm
24 90.3 gsm 65.0 gsm 52.7 gsm 43.4 gsm 35.6 gsm
28105.4 gsm 75.8 gsm 61.5 gsm 50.7 gsm 41.5 gsm
60225.8 gsm 162.4 gsm 131.7 gsm 108.6 gsm 88.9 gsm
67252.1 gsm 181.3 gsm 147.1 gsm 121.2 gsm 99.3 gsm
80301.0 gsm 216.5 gsm 175.6 gsm 144.8 gsm 118.5 gsm
110413.9 gsm 297.7 gsm 241.4 gsm 199.1 gsm 163.0 gsm