When it comes to mailing, envelope weight isn’t just about grams or ounces—it’s about meeting USPS requirements and keeping costs in check. Understanding how paper basis weight and thickness are measured can help you choose the right envelope and avoid surprises.
How Much Does an Envelope Weigh?
Paper can be described in terms of both its basis weight and its thickness; the same #10 envelope can be described as having both 24# paper basis weight and a paper thickness of 4.9 mils. Paper basis weight is a more common way to describe paper and should be used when ordering paper-based products like envelopes.
What is Basis Weight and How is it Calculated?
Basis weight, sometimes referred to as substance weight, describes the collective weight of the fibers that make up the paper, calculated as the weight of 500 17” x 22” sheets. An envelope made from 20# paper represents the weight of 500 17” x 22” sheets of that paper and not the 6.75 gram #10 envelope itself.
Weighing Your Paper Options
There are many factors involved in choosing the right basis weight for your mailing. These factors include the thickness of the contents going in the envelope, the number of inserts and the type of mechanical insertion equipment being used. Nonetheless, the most commonly used basis weights for common envelope sizes are:
Common Envelope Sizes and Paper Basis Weights
(Bond-Grade Paper)
| Common Envelope Size | Paper Basis Weight |
|---|---|
| #9 envelopes | 20# – 24# paper |
| #10 envelopes | 20# – 24# paper |
| 6×9 envelopes | 24# – 28# paper |
| 9×12 envelopes | 24# – 28# paper |
Weighing Paper Caliper
Paper can also be described in terms of its thickness. It is also commonly referred to as caliper thickness from the gauge used to measure paper thickness, a caliper. Caliper thickness is expressed in thousandths of an inch (mils) and is given in ranges to account for normal variances in the paper.
Paper Basis Weight
(Bond-Grade Paper) to Nominal Caliper Comparison Chart
| Basis Weight (bond) | Nominal Caliper (mils) |
|---|---|
| 20 | 4.2 – 4.4 |
| 22 | 4.5 – 4.7 |
| 24 | 4.8 – 5.1 |
| 28 | 5.2 – 5.7 |
Download Our Envelope Basics Guide
Envelope Basics is a complete guide that details everything you need to select, measure and order the right envelope for your mail campaign.
Whether you’re a seasoned mailer or new to the mail industry, Envelope Basics includes helpful tips for your business or organization. Download your copy of Envelope Basics here.
Partner with a Paper Expert
For nearly 140 years, Tension has delivered high-quality envelopes through strong partnerships with trusted paper suppliers. We know what matters — from basis weight to thickness — and ensure every envelope meets our standards. Contact a Tension Sales expert to discuss your paper and envelope needs.
