Sometimes you see a paper’s weight listed at “20 pounds” while other times you might see something like 75 grams per square meter (“gsm” for short). What’s the difference? How do you convert from one measurement to the next?
Paper Weight Explained
Like almost any there measurement, there are different systems to describe the same thing. With paper you have the standard United States system (pounds) vs. the internationally accepted metric system (grams).
The measurement is describes the thickness of the paper, regardless of the size.
These system is usually known as the “paper weight” but that’s often confused with a “paperweight,” as in the thing that stops papers on your desk from blowing away when a fan is on, so you also hear the term “grammage” to describe what we are talking about here.
Paper weight can be measured in pounds, as in “This is 20 pound paper” where you’d typically leave off the dimensions associated with the weight. When talking in grams, as in “75 gsm paper” you’ almost always note that the measurement is based on a square meter. For reference 20 pound and 75 gsm paper are of equivalent thickness.
There is more to it though, as if paper weighs 75 grams per square meter, it clearly doesn’t weigh 20 pounds per square foot. That’s because metric countries — mainly Europe — measure by the square meter while the US measures in pounds per ream (500 sheets).
But we all know that 500 sheets of 8.5 x 11 paper doesn’t weigh 20 pounds. So what’s up?
A 20 pound paper weighs 5 pounds, because the 20 pound measurement uses uncut sheets of paper, which are 17″ x 22″ sheets. Those sheets are 4x the size of an 8.5″ x 11″ paper, hence the 20 pound weight.
Paper Weight Conversion
These equivalencies apply to common copy or “bond” paper.
Paper Usage By Weight
You can use paper however you’d like, but the general rule of thumb for paper use is below:
- 20 lb: copy paper for most printing and copying, normal notebooks like Moleskine paper
- 24 lb: laserjet printing, heavy notebooks and fountain pen paper
- 28-30 lb: letterhead