Calculate the weight, basis weight, or grammage of paper

We print a lot of music, and use a lot of paper, at NYC Music Services.

I’ve opined before on the size of music paper — that is, dimensions upon which the image of the music appears, and you can read all about that here. But what about the weight of the paper? And what do we mean when we say “weight”, anyway?

Pound for pound

Sometimes we are talking literally about how heavy the paper is if you put it on a scale. That’s helpful to know if you have just printed music and need to ship it — often, rather quickly — and are obliged to calculate the weight of the packages before you transmit them to the shipper.

But often when we say “weight” when referring to paper, we really mean the basis weight — and that’s where things can to get confusing. Did you know 20 lb. and 50 lb. paper are the same weight??? And how come a “ream” of 20 lb. office paper only weighs 5 lbs., and not 20 lbs.?

The basis weight or “paper weight” is measured in pounds per 500 standard sheets within its type. Each “type” of paper’s standard sheet is different. (And you were supposed to know this because…?)

There are plenty of resources devoted to the minutiae of this, but, in our above example, typical office paper is often labeled “20 lb.” If you look closely, more specifically, it’s “20 lb. bond” (sometimes called “writing” paper). “Bond” refers to the paper type, and bond paper’s standard sheet size is 17″ x 22″. So, 500 sheets of 20 lb. paper at the standard size of 17″ x 22″ weighs… you guessed it, 20 lbs.

But 17″ x 22″ is awfully large. Here in North America, office paper is “letter” size, which is 8.5″ x 11″. Yes, that’s exactly half of the standard bond size, in each direction. So, if you cut a 17″ x 22″ bond sheet in four equal parts, you’ll get four letter-size sheets.

And that’s why a 500-sheet ream of 20 lb. office paper weighs 5 lbs.

What to make of the equivalence between 20 lb. and 50 lb. paper? Well, that’s because the former refers to the “bond” basis weight, whereas the latter refers to the “text” basis weight (also called “offset” or “book” weight). This paper’s standard sheet size is 25″ x 38″. Do the math, and you’ll find that the area of a sheet of text paper is about 2.5 times larger than that of a sheet of bond paper — hence, the basis weight is also 2.5x more.

Measure for measure

Believe it or not, we’ve only just gotten started. There are many different paper types, and thus many different basis weights.

Bond	Text	Tag	Index	Bristol	Cover	gsm
16	40	37	33	27	22	60
20	50	46	42	34	28	75
24	60	55	50	41	33	90
28	70	65	59	48	39	105
32	80	74	67	55	45	120
36	90	83	75	62	50	135
40	101	92	83	68	55	150
44	111	101	91	75	61	165
48	122	111	100	82	67	180
53	135	123	111	91	74	200
59	150	135	122	100	81	220
64	162	147	133	109	89	240
67	170	154	138	114	92	250
70	176	160	144	119	96	260
72	183	166	150	123	100	270
80	203	184	166	137	110	300
94	236	215	194	160	130	350

Notice the last column on the chart above. Our metrically inclined friends have tried to make it easier by creating a unit of measurement known as “grammage”, or grams per square meter, often abbreviated as g/m² or gsm, which thoughtfully includes both the weight and the area into a single unit of measurement. Theoretically, this makes it possible to have apples-to-apples comparisons of paper thickness. Unfortunately, the grammage is often in little-bitty-type:

So at least here in the US, it is far more common still to refer to, i.e., “28 lb.” or “80 lb.” paper, and, what’s more, it’s generally understood that the smaller numbers from “16 lb.” to “36 lb.” refer to the bond weight, whereas the larger numbers from “40 lb.” to “100 lb.” refer to the text weight.

Here’s an example. Neenah Classic Crest Solar White Smooth Paper is sold as “8 1/2 x 11 in 28 lb Writing” (remember “writing” is synonymous with “bond”):

And as “12 x 18 in 80 lb Text”:

Is the 80 lb. paper really nearly 300% heavier than the weight of the 28 lb. paper? No.

If we compare the specs “apples-to-apples” and use gsm as our unit of measurement, we notice that the 28 lb. bond (writing) paper is 105 gsm and the 80 lb text paper is 118 gsm — only about a 13% difference:

More than once I’ve not checked carefully and ordered the wrong type of paper, especially when purchasing cover stock, where the commonly used weights are a similar range of numbers as text weights. So, be sure to look closely.

Apples to apples

Charts like the one above are helpful, but an interactive calculator that not only figured equivalent basis weights, but also the actual weight of paper — like when it’s placed on a scale — would be really handy. I even toyed with creating one myself, until I realized that someone had already done it. The Paper Weight Calculator, available from Omni Calculator and embedded here with their permission (and also on our Resources page at NYC Music Services) can convert between grammage and basis weight and to find what the grammage of paper is. Then, you can select the size of your paper (and even input custom sizes if your size isn’t available from the preset menu), input the quantity of sheets, and determine the actual weight. Try it out!

For instance, let’s say I need to print and ship a set of parts for and orchestral work with 75 parts, and each part is 12 pages long. We typically print parts on 80 lb. text weight paper at 9″ x 12″ size, so 12 pages bookletized uses 3 sheets of 12″ x 18″ paper, which is 225 sheets. (If you do this regularly you’ll want our PDF Batch Utilities to make quick work of this.)

For Basic sheet size I’d select Text; Basis weight would be 80 lb; Paper size would be Arch B (12 in x 18 in), and Quantity would be 225. All other fields are calculated on the fly by the calculator, and I can see that the actual weight of the parts will be 8.185 lbs.

I might add a couple of pounds to account for packing material and the shipping box, but this is a very helpful way of quickly estimating the shipping weight of a set of music and using it to obtain accurate shipping & handling costs.

A numbers game

Fun fact: Before the time of digital printing and the rise of “digital” paper sizes like 12″ x 18″, music was often copied on 9.5″ x 12.5″ paper, which was 12.5″ x 19″ folded in half. Why such a seemingly strange size? Remember that parent sheet “text” size of 25″ x 38″? Yes, it was that paper, cut in half each way.

Did you find this useful? Do you have additional tips to share? Let me know in the comments.