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Paper Specifications: What does Caliper mean?

A thickness gauge measuring the combined caliper of two sheets of paper

What is Paper Caliper?

When referring to the specifications of a paper stock, the thickness of a single sheet is known as the paper's "Caliper."

In the United States, and other countries that use the Imperial measurement system, a paper's caliper is typically expressed in thousandths of an inch. For example, common 20# Bond paper has an average caliper of .004", which is 4/1000ths of an inch.

A person using a thickness gauge to measure a paper's caliper
Measuring a paper's caliper with a thickness gauge

Points, Mils, and Microns

Each thousandth of an inch increment is referred to as a "point." Hence, a thickness of .001" equals 1 point, a thickness of .002"equals 2 points, and so on. Since 20# Bond has a caliper of .004", its thickness could be stated as being 4 points (commonly written as 4pt).

In addition to being known as a "point", every .001" in thickness is also sometimes called a "mil." Thus, one point equals one mil, and both refer to a measurement of .001". By the way, the term "mil" has nothing to do with a metric millimeter. The reference to "mil" originated from the French word "mille", which means 1,000.

Countries that use the Metric system express miniscule measurements, like a paper's caliper, in fractions of a millimeter or in microns. A micron is one one-thousandth of a millimeter and a millimeter is one one-thousandth of a meter. This means that one micron is one one-millionth of a meter.

A digital micrometer and a traditional micrometer
An example of a digital micrometer and a traditional micrometer

What Devices are used to measure a Paper's Caliper?

A standard ruler or tape measure obviously isn't capable of measuring to the thousandth of an inch or in microns. Therefore, a precision measuring device - such as a micrometer or thickness gauge - is required to obtain an accurate measurement.

Micrometers are available in either the traditional analog style or with a digital readout. Similarly, thickness gauges will either have a mechanical dial or a digital display.

A sampling of sheets can be measured individually, or a bundle of sheets can be measured together. Of course, if a bundle is measured, the result will need to be divided by the number of sheets in the bundle to get the average thickness of each sheet.

A stack of white paper sheets
Paper is available in a variety of different calipers to suit every type of print project

Why is the Caliper of Paper important?

There are many different calipers of paper from which to choose. This is because different printing applications call for different thicknesses of paper.

For example, a direct-mail postcard needs to be thick and sturdy because it won't have an outer envelope to protect it during transit. On the other hand, letterhead will travel within an envelope so it can be made from a lighter text weight paper.

A bound book is another example. The inside pages must be thin and supple enough to turn easily. However, the outside cover often requires a degree of thickness and rigidity to add durability to the book.

Additionally, promotional materials produced in bulk usually have a moderate paper thickness. This helps strike a balance between providing high-quality print literature and minimizing the production cost.

Color Vision is here to help!

The caliper of a paper stock provides a fundamental basis for determining which paper to use for a certain application. If you need help figuring out the best paper thickness to use for a particular project, get in touch with Color Vision and we will be happy to help.

Just give us a call at 800-543-6299 to discuss your project. Or, if you are looking to get a price quote, use our simple Quote Request form to send us your specifications and we will email a quote to you.

Whatever your printing needs may be, we look forward to assisting you!

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