The Unlimited Guide of Understanding Paper Weight and Thickness

We’re all familiar with paper, but some terms related to paper weight and thickness might seem confusing. Don’t worry! After reading this article, you’ll understand the meaning of GSM, LBS, PT, and MM, and how to convert between them like a pro.

Paper Weight and Thickness

Before diving into the complexities of paper measurements, let’s first understand the basics of paper weight and thickness.

Paper Weight

Also known as “grammage,” paper weight refers to the weight of a single sheet of paper, usually measured in grams per square meter (g/m²). It’s an indicator of how heavy or light the paper is. But this measurement is not as simple as just weighing a single sheet.

In fact, paper weight is determined by the weight of a ream (500 sheets) of uncut paper in a standard size. That’s why you often see terms like “54 lbs” or “80 GSM” used to describe paper weight. Paper weight impacts many aspects of its performance, such as opacity, feel, and durability for tasks like mailing.

Paper Thickness

Thickness refers to the physical measurement of a single sheet of paper, usually in points (pt) or millimeters (mm). This value is typically much smaller than weight and tells you a lot about the paper’s hardness and potential uses. For example, thicker paper may be suitable for business cards, while thinner paper is ideal for books that need to be flexible and easy to handle.

What is GSM?

GSM stands for “grams per square meter” and is the international standard for measuring paper weight. When we talk about GSM paper, we’re referring to the weight of one square meter of paper (in grams).

The higher the GSM, the thicker the paper. It’s that simple. Higher GSM paper usually indicates better quality because it’s thicker and more durable. However, keep in mind that greater thickness doesn’t always mean heavier weight. It depends on the material you are measuring. Higher-quality paper might not suit your specific needs, so always consider the quantity and quality you need and its impact on shipping or mailing costs.

Here are some common GSM ranges and their uses:

● 35-55 GSM: Newspaper – This paper is very thin and fragile.

● 90-100 GSM: “Printer Paper” – Similar to the paper we use in home or office printers.

● 120-140 GSM: Posters and Flyers – This paper is a bit thicker than regular printer paper.

● 210-300 GSM: Brochures and Magazine Covers – More durable and resistant to bending.

● 350-400 GSM: Greeting Cards and Business Cards – This is the thickness level commonly referred to as cardstock, used for packaging and printing business cards or wedding invitations.

What is LBS?

LBS (pounds) is the weight measurement unit used in the United States, based on the weight of 500 sheets of a specific paper size. For example, if the paper is described as “100 lbs” or “100#,” it means the weight of 500 sheets of paper in that size is 100 pounds.

Note that the “basic size” may differ depending on the type of paper, so a ream of card stock might have a different size than a ream of text paper.

What are PT and MM?

PT (Points) is used to measure the thickness of paper in North America. One point equals one-thousandth of an inch. For example, a paper thickness of 10 pt is equal to 0.01 inches.

This measurement is especially useful when considering the paper’s stiffness and suitability for use. The higher the PT, the thicker and stiffer the paper. PT is commonly used in the printing industry for describing cardstocks and other rigid papers, such as kraft paper and grayboard, where the tactile feel is important.

● 3 to 6 pt paper weighs around 60 GSM to 120 GSM – ideal for photocopy paper and lightweight flyers.

● 9 pt to 14 pt paper weighs 199 GSM to 300 GSM – perfect for posters and more durable marketing materials.

● 14 pt paper typically starts from about 310 GSM – used for labels, tags, and thick covers.

MM (Millimeters) is the metric unit used for measuring paper thickness. One millimeter equals 1,000 microns or 1/1,000 of a meter. This precise measurement unit is typically used alongside GSM for a more complete view of paper characteristics.

Converting Paper Weights

LBS to GSM Conversion

1 pound = 453.592 grams1 square inch = 645.16 square millimeters

Here’s the conversion formula:

GSM = LBS x 1.48 (for book papers)GSM = LBS x 2.71 (for cover stocks)GSM = LBS x 3.73 (for bond papers)GSM = LBS x 1.63 (for newsprint)

This simplified formula allows you to convert LBS to GSM.

PT to LBS Conversion

Converting PT to LBS is not a direct process because the paper’s density also impacts its weight. However, we can approximate:

● 8 pt card stock might be around 80 lb cover stock, but this can vary depending on paper type.

Below are the main paper classifications in North America and their standard sizes.

PT to GSM Conversion

To convert PT to GSM, the process is similar to the PT to LBS conversion. Here’s a simple guide for card stock covers:

Paper Thickness Reference

Even if the weight is the same, the thickness of different types of paper can vary. Typically, coated papers are thicker than uncoated papers at the same GSM.

Here are some examples of paper thickness for different GSM values:

Conclusion

Understanding paper weight and thickness is essential for making informed decisions about custom packaging. Knowing the right GSM, LBS, PT, and MM helps you choose the best paper for your project, ensuring the desired durability, flexibility, and appearance. Whether you’re creating flyers, brochures, or luxury packaging, the right paper makes all the difference.