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 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 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.

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, 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

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 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)

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)

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.

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.

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.

^{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

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 80-110 gsm, are typically used for newspapers and everyday printing, and text of coloring books, text books, booklets, novels, notebooks.
• Mid-weight papers, like 120-140 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.

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