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Paper Weight: GSM, LB, PT, MM

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Paper Weight Conversion

 

In the printing and paper industry, understanding paper weights is like speaking a second language. It’s essential for choosing the right type of paper for your project, whether you’re a graphic designer, a publisher, or simply looking to get some flyers printed for your small business. In this lengthy exploration, I’ll be diving deep into the intricacies of paper weight, explaining the differences between gsm, lbs, pt and mm, and how to convert between these units.

 

paper thickness

 

Paper is a versatile material used in a myriad of applications, from printing books and brochures to creating art and packaging. But not all paper is created equal. The weight and thickness of paper can affect its feel, its ability to be printed on, and its suitability for certain tasks. Before diving into the complex world of paper metrics, let’s understand the basics of paper weight and thickness.

 

Paper Weight

 

Paper weight is also called “gram weight”. Paper weight refers to the mass per square meter of paper or cardboard, expressed in g/㎡. Paper weight is a measure that reflects the heaviness of paper. However, this measurement isn’t as straightforward as weighing a sheet on a scale. Instead, paper weight is determined by the weight of a ream (500 sheets) in its uncut size, which varies depending on the type of paper. This is why you’ll often see paper described in terms like “54 lb” or “80 gsm.” The weight of the paper can influence many aspects of its performance, such as opacity, how it feels in the hand, and its sturdiness for tasks like mailing.

 

Paper Thickness

 

Thickness, on the other hand, refers to the actual physical measurement of a single sheet of paper. This measurement is typically much smaller than weight and is often measured in points (pt) or millimeters (mm). Paper thickness can tell you a lot about the rigidity and potential uses of a paper stock. For instance, a thicker paper could be ideal for a business card that needs to feel substantial and durable, whereas a thinner paper might be preferable for a book that needs to be flexible and easy to handle.

 

What’s GSM Meaning

gsm paper meaning

GSM is an acronym for grams per square meter and is an international standard for measuring the weight of paper. When we talk about what is gsm paper, we’re referring to the weight of the paper in terms of how much a single sheet of one square meter weighs in grams.

GSM is a very straightforward measurement because it doesn’t vary with the sheet’s size. This means that whether you have a tiny A5 sheet or a large A0 poster, if they’re both 80 gsm paper, they weigh the same per square meter. GSM provides a precise and consistent method for comparing the weight and, to a certain extent, the thickness of different types of paper.

 

What’s LBS Meaning

 

Lbs, or pounds, is the weight measurement used in the United States and is based on the weight of 500 sheets (a ream) of the basic size of a particular paper type. For example, if the paper is described as “100 pounds” or “100#” means that the paper weight is 100lb. It’s important to note that the “basic size” can differ depending on the paper type, so a ream of cardstock may have a basic size different from a ream of text paper.

lb in paper weight

Paper types Standard size
Bond paper 17″ x 22″
Cover paper 20″ x 26″
Text paper 25″ x 38″
Index Bristol 25.5 x 30.5″
Mill Bristol 22.5 x 28.5″ / 22.5 x 35″
Newsprint 24″ x 36″

 

For example:

The basic size for bond paper is 17″ x 22″, and if 500 sheets at that size weight 80 pounds, the paper is classified as 80 lb.

The basic size for cover paper is 20″ x 26″, and if 500 sheets at that size weight 80 pounds, the paper is classified as 80lb.

The basic size for text paper is 25″ x 38″, and if 500 sheets at that size weight 80 pounds, the paper is classified as 80lb.

The basic size for Index Bristol is 25.5″ x 30.5″, and if 500 sheets at that size weight 80 pounds, the paper is classified as 80lb.

The basic size for Mill Bristol is 22.5″ x 28.5″ and 22.5″ x 35″, and if 500 sheets at that size weight 80 pounds, the paper is classified as 80lb.

The basic size for Newsprint is 24″ x 36″, and if 500 sheets at that size weight 80 pounds, the paper is classified as 80lb.

This measurement can be confusing because the basic size differs among types of paper, which is why GSM is often used alongside LBS for clarity.

 

What’s PT Meaning

 

PT paper

 

PT, or points, is a measure of paper thickness rather than weight. One point is equivalent to one-thousandth of an inch. Therefore, if a piece of paper is 10 pt, it is 0.01 inches thick.

This measurement is particularly useful when considering the stiffness of paper; the higher the pt, the stiffer and thicker the paper will be. In the printing industry, pt is often used to describe the thickness of cardstocks and other rigid papers(like Kraft paper, gray board), where the physical feel of the paper is a significant attribute.

 

What’s mm Meaning

 

mm paper meaning

 

When we talk about mm in the context of paper, we are referring to millimeters, a metric measurement of thickness. Millimeters provide a precise measure of a paper’s thickness and are often used in conjunction with GSM to give a full picture of a paper’s characteristics. This is particularly useful when you need to ensure that paper will not only have the right weight but also fit into specific printing machines or enclosures.

 

Paper Weight and Thickness Conversion

 

Know about the paper weight and thickness conversion can help you determine the weight of a paper sheet of any size, gram weight and basis weight.

Converting between gsm, lbs, pt and mm is essential for anyone working internationally or with different types of paper. These conversions help us to compare paper types and ensure that we’re selecting the right weight and thickness for our needs. Let’s break down each type of conversion.

 

Convert gsm to lbs or lbs to gsm

 

To convert gsm to lbs or lbs to gsm, we need to identify the “basis size” of the paper we’re working with because lbs measurements are based on the weight of a ream of this size rather than a standard square meter. Once the basis size is known, we can use a conversion chart or calculator to find the equivalent lbs. There are online tools available that can perform this conversion automatically, but having a basic understanding of the math involved can be quite helpful.

 

GSM to Lb Formula

1 gsm = 0.676 lb Text paper. Multiply each gsm by 0.676.

1 gsm = 0.369 lb Cover paper. Multiply each gsm by 0.3695.

For example:

200gsm text paper = 135.2lb (200 x 0.676)

200gsm cover paper = 73.9lb (200 x 0.3695)

 

Common GSM to LBS Formula
Cover (gsm) Cover (lb) Text (gsm) Text (lb)
157gsm 58lb 80gsm 54lb
200gsm 73.9lb 100gsm 67.6lb
250gsm 92.4lb 105gsm 71lb
300gsm 110.8lb 120gsm 81lb
350gsm 129.3lb 128gsm 86.5lb
140gsm 94.6lb
157gsm 106lb
160gsm 108lb
200gsm 135lb

 

LBS to gsm Formula

1 lb of Text paper = 1.48 gsm. Multiply each pound of text paper by 1.48.

1 lb of Cover paper = 2.708 gsm. Multiply each pound of cover paper by 2.708.

For example:

70lbs text = 103.6gsm (70 x 1.48)

70lbs cover = 189.56gsm (70 x 2.708)

 

Common LBS to GSM Formula
Cover (lb) Cover (gsm) Text (lb) Text (gsm)
60lb 162.5gsm 50lb 74gsm
70lb 189.6gsm 60lb 88.8gsm
80lb 216.6gsm 70lb 103.6gsm
90lb 243.7gsm 80lb 118.4gsm
100lb 270.8gsm 90lb 133.2gsm
110lb 297.9gsm 100lb 148gsm
120lb 325gsm 110lb 162.8gsm
130lb 352gsm 120lb 177.6gsm
130lb 192.4gsm

 

PT to lb paper conversion

 

When converting from pt to lb paper, we’re moving from a measurement of thickness to one of weight. This isn’t a straightforward conversion because the density of the paper can affect the weight independently of thickness. However, general guidelines and charts can give us a rough equivalence between these measures. For example, a 8 pt cardstock might be roughly equivalent to an 80 lb cover stock, though the actual weight can vary based on the specific type of paper.

 

Common PT to LB Formula
Cardstock Cover (PT) Cardstock Cover (LB)
8pt 80lb
12pt 90lb
14pt 111lb
16pt 129lb
18pt 148lb

 

PT to gsm paper conversion

 

The conversion from pt to gsm paper thickness is similar to converting pt to lb, but we’re looking for an equivalent weight in the metric system. As with lbs, this conversion can be complex because it must account for the density of the paper. Charts that correlate pt to gsm can give a general idea, but for precise conversion, specific calculations based on the paper’s characteristics are necessary.

 

Common PT to GSM Formula
Cardstock Cover (PT) Cardstock Cover (GSM)
8pt 200gsm
12pt 250gsm
14pt 300gsm
16pt 350gsm
18pt 400gsm

 

Paper thickness pt to mm

 

For those working in a system that uses millimeters, converting paper thickness from pt to mm can be essential. Since one point is equal to 0.001 inches, converting to millimeters involves multiplying the pt value by 0.0254 (since one inch equals 25.4 mm). Therefore, if you have a 10 pt paper, that would be 10 x 0.0254, which equals 0.254 mm thick.

 

Common PT to MM Formula
PT Inches mm
8pt 0.008″ 0.203mm
10pt 0.01″ 0.0254mm
12pt 0.012″ 0.0305mm
14pt 0.014″ 0.0356mm
16pt 0.016″ 0.0406mm
18pt 0.018″ 0.457mm

 

Paper Thickness Reference

 

Usually when we talk about the thickness of the paper, it is expressed in grams, but when printing and binding, we need to know the thickness of the page to calculate the thickness of the spine reserved for the cover. Even the same weight, different types of paper, the thickness is different. Usually, in the same GSM, the uncoated paper is thicker than coated paper.

Below listed 7 types of paper thickness. Just for reference, different brand and supplier of paper, the thickness will have a bit of difference.

1 inch =25.4mm

 

Offset Paper
GSM Thickness(mm) Thickness(inch)
60gsm 0.08mm 0.0031″
70gsm 0.09mm 0.0035″
80gsm 0.01mm 0.0039″
100gsm 0.12mm 0.0047″
120gsm 0.14mm 0.0055″
140gsm 0.16mm 0.0063″
160gsm 0.18mm 0.0071
180gsm 0.22mm 0.0086
200gsm 0.24mm 0.009
230gsm 0.28mm 0.011
250gsm 0.29mm 0.0114
300gsm 0.35mm 0.0137

 

Glossy Art Paper
GSM Thickness(mm) Thickness(inch)
80gsm 0.06mm 0.0024″
105gsm 0.09mm 0.0035″
128gsm 0.12mm 0.0047″
157gsm 0.14mm 0.0056″
200gsm 0.18mm 0.0071″
250gsm 0.25mm 0.0098″
300gsm 0.32mm 0.0123″
350gsm 0.36mm 0.0142″

 

Matte Art Paper
GSM Thickness(mm) Thickness(inch)
80gsm 0.08mm 0.0031″
105gsm 0.1mm 0.0039″
128gsm 0.13mm 0.0051″
157gsm 0.16mm 0.0063″
200gsm 0.2mm 0.0079″
250gsm 0.26mm 0.0102″
300gsm 0.29mm 0.011″

 

Coated One Side Paper
GSM Thickness(mm) Thickness(inch)
210gsm 0.28mm 0.011″
250gsm 0.35mm 0.0138″
300gsm 0.42mm 0.0165″
350gsm 0.49mm 0.0193″
400gsm 0.56mm 0.022″

 

Gray Board
Thickness(mm) GSM Thickness(inch)
1mm 600gsm 0.0394
1.5mm 900gsm 0.0591
2mm 1200gsm 0.0787
2.5mm 1500gsm 0.0984
3mm 1800gsm 0.1181

 

Kraft Paper
GSM Thickness(mm) Thickness(inch)
60gsm 0.10mm 0.0039″
80gsm 0.12mm 0.0047″
120gsm 0.17mm 0.0067″

 

Bible Paper
GSM Thickness(mm) Thickness(inch)
30gsm 0.04mm 0.0016″
32gsm 0.04mm 0.0016″
35gsm 0.05mm 0.00197″

 

 

Common Usages for Different Thicknesses

 

Understanding the common usages for different paper thicknesses can help in selecting the appropriate paper for a project.

  • Thinner papers, such as 30-50gsm, are typically used for text of bibles, poetry, dictionary.
  • Lightweight papers, such as 80-90 gsm, are typically used for newspapers and everyday printing, and text of coloring books, text books, booklets, novels, notebooks.
  • Mid-weight papers, like 100-140 gsm paper, are suitable for letterheads and stationary, text of catalog, books, high-end planners/journals.
  • Thicker paper, such as 157-200 gsm, are often used for posters and flyers, high quality color text of children’s books, art books, photo books, coffee table books and marketing materials. When it comes to cardstocks, the thickness measured in pt becomes especially relevant.
  • Heavier weights, such as 200gsm-350gsm-these highest paper is common used for book covers, flashcards, game cards, calendars,etc.
  • A 8-12 pt cardstock is common for business cards, packages, 14-16 pt cardstock (C1S paper) is common used for board books, playing cards, heavy covers, luxury packages, etc.

 

Navigating the world of paper weight requires an understanding of gsm, lbs, and pt, as well as how to convert between these units. Whether you’re creating business materials, setting up for a print job, or just curious about paper specifications, mastering these measurements will ensure that you make informed decisions about the paper you use, resulting in a final product that meets your expectations and communicates quality to your audience.

 

If you want to know more about the popular paper and paper weight, please click here. Any question about printing project, please contact our experts.

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