Converting Paper Weight In Pounds To Gsm

[alexwi]

The idiotic (because let's be honest, there's no other word for it) insistence on using equally idiotic units for measuring things in the US is very telling of this culture's willingness to embrace change. I used to think that having landed on the moon despite this was irrefutable proof of God's existence, but then I learned that all the calculations where done in SI units (after all, NASA's program owed much to the nazis' R & D in this area.

 

It is only in the realm of illegal drugs that people here are familiar with the Kilogram, so don't expect to be understood when asking for 100 grams of ham. The one time I had the crazy idea of asking for 0.3 POUNDS of something at the deli, it took three people to get it right).

 

Anyway, paper...

 

We measure paper in pounds, but pounds of what? For regular paper (y'know, the one we buy in reams of 500 sheets), that would be the weight of 500 22" x 17" sheets of paper. Why 22" x 17"? Because that's the size those sheets come in before they're cut (i.e. one such sheet produces 4 letter-sized sheets when cut twice or 2 11" x 17" sheets). I'm sure there's some history behind this, going back to the colonial period, but who knows. You can learn more than you ever wanted to by visiting wikipedia's entry on the subject: https://en.wikipedia.org/wiki/Paper_size#Standardized_American_paper_sizes

 

To make things more confusing, which is something we have extraordinary talent for, that base size - 22" x 17" - does NOT apply to all kinds of paper. Some kinds of paper use other "basis sizes." See https://pariscorp.com/paper-weight-guide/

 

Europeans, who are far more rational than we are, and this probably originated in Germany, whose people have a knack for norms (and also because I can't imagine, for example, people who run away from loose bulls on the streets would be interested in any of this), came up with an equally rational approach: let's weigh a SINGLE 1-square meter sheet.

 

The short of it is that to convert paper poundage (couldn't come up with another term) to gsm, you must multiply pounds by 3.76. Conversely, to make the inverse calculation, you must divide by 3.76.

 

The math:

 

22" x 17" = 0.2413 square meters.

0.2413 m² x 500 sheets = 120.65 m²

1 Lb = 454 grams

 

454 g / 120.65 m² = 3.76 g/m² or gsm.

 

Alex

[samasry]

Very Interesting analysis

 

Due to my bad memory, the rule  I  have  been using for a while is that  the 24-lb  paper and the 90-gsm paper are about the same weight, at least  extremely close.

 

This can  help anyone  derive the scale factor back and forth, in case   they are like me and can not keep a number like 3.76  in their head for long.

 

 

[hbdk]

For someone who would really like to dive into the topic of paper (sizes, weight etc.), I highly recommend:

 

https://www.papersizes.org/