Before your business begins a paper-based project, it's important to know the paper's weight. Fortunately, with a little simple math and a few measurements, you can find out the weight of your paper in grams per square meter, even if you don't have the original packaging for your paper.
The micron is a standard measurement of length in the metric system that’s the equivalent of one-millionth of a meter.
Gsm stands for “grams per square meter.” When used in the context of measuring the weight of paper it is also referred to as “grammage.” It is the equivalent of 0.001 kilograms per square meter.
The challenge is that there’s no real direct one-to-one correlation between microns and gsm. That’s because microns measure the thickness of paper, while grams per square meter measures the weight of paper.
For an example, two people can each weigh 150 pounds, but not be the same at all. If one person is 5’11” tall, and the other is 5’2”, there will be a significant difference between the two physical bodies in space.
However, you can convert microns to gsm with a few tools and a simple calculation.
It’s important to understand a few basic terms when you’re converting microns to grammage for your business paper needs.
Basis Weight: The measurement in pounds of the weight of 500 sheets of paper. Basic sheet size will not be the same for all types of paper, so keep in mind that basis weight can vary widely.
Bulk: This is the paper’s thickness compared to its weight. A low-bulk paper will be thinner and more compact in size and feel than a high-bulk version of the same weight and size.
Caliper: The thickness of a single sheet of paper, measured in thousandths of an inch, as measured by a micrometer. Generally speaking, there is a directly proportional relationship between caliper and basis weight. In other words, the thicker the paper or the greater the caliper, the more the paper weighs.
In order to calculate both microns and grams per square meter, you’ll need the following tools:
- Measuring tape
- Gram scale
To convert microns to grammage or grams per square meter, measure the mass and the volume of a large stack of the paper with which you’re working. These measurements should be calculated in grams and centimeters cubed, respectively.
To find the volume, multiply the width and height from the label of the paper packaging by the thickness of the stack of paper. Measure the thickness yourself with the measuring tape or micrometer.
Look at the package label to find the size of the paper. In this example, it's 20 x 28 cm. Use a measuring tape to find the thickness of the stack, which is 2.5 cm in our example. Multiply all three figures to find the volume. 20 x 28 x 2.5 = 1,400 cc.
Find the paper’s density by dividing the mass (in grams) by the volume (in cubic centimeters).
The paper's mass is approximately 2,268 grams. The volume is 1,400 cc. 2268 divided by 1400 equals 1.62.
Next, convert the density into a micron-based measure by dividing the density by 100. There are 100 times as many grams per meter as there are per centimeter and a millionth as many grams per micron as per meter. (100x100/1,000,000 = 1/100.)
The density is 1.62. Divide this by 100 and the total is 0.0162 microns.
Multiply the sheet thickness in microns by the conversion factor from the previous step to get grams per square meter (gsm).