This discrepancy can affect your shipping invoice, as a mailer that is ordered at 12” ends up at 11.94” or 12.06”. Custom mailer packaging thus demands numbers that have a limit on each of its sides. This is a guide to the limits you should be aware of, how they relate to carrier billing, and how to determine them on a sample. Empress Packaging produces custom mailer packaging for wholesale purchasers throughout the USA.
What is the proper level of tolerance for a mailer?
Ask your supplier to write it down and compare it to a published buyer standard. For boxes 4-25 inches, Snap-on’s supplier standard is General Requirements for wholesale printed mailer boxes plus or minus 1/16 inch, and or minus 1/8 inch for boxes 26-50 inches. It uses the limit when adjacent panels are at right angles. It can also be used to measure the inside length and width of the glue joint from the inside of the liner surface and check it based on the ASTM D2658 box gauge method. Write the convention used for corrugated mailer packaging on the order, regardless of the convention you use.
How does a 1/16-inch make a difference in the bill?
Since August 18, 2025, FedEx has been rounding dimensions of each package to the nearest inch, according to Atlantic Packaging and iTape. Go outside with a mailer that is marked 12 x 11 x 4. At the common divisor of 139, it measures 528 cubic inches, which is 3.8 pounds, billed as 4. FedEx rounds the length that the plant provides, which is 12.06, to 13. The resulting custom size shipping mailers is reported to have a weight of 4.1 pounds (572 cubic inches), but it is advertised as weighing 5 pounds. That increases the weight of a light product by a pound per package. Check with your own agreement regarding rounding.
What would you use to test it on a sample?
Make 10 measurements in order to observe the spread. Install each with the panels square, read the panel length, width, and height at two locations, and record the minimum and maximum values. Take a photo of the ruler in one box for the file, so that the next lot can be measured in exactly the same manner. Is there any reading that goes out of your window? That answer will indicate whether or not the nominal size should be moved, or if the plant should tighten its process prior to a bulk run.
What other factors should be capped?
Curl matters too. A blank that comes curled will unroll anything from square, and the inside dimensions will change as it unrolls. Know the degree of curl that the plant will tolerate, and place 10 blanks on a table on the dock, unfolded, and search for gaps.
FAQS
Q: What is the minimum quantity of wholesale printed mailer boxes that must be ordered?
A: Set it up (structure and print). Compare the printed and plain box order prices when ordering boxes for bulk mail at three quantities.
Is there a smaller tolerance that a plant can hold?
Some can. Inquire about the price/amount that the plant is quoting, how the plant verifies that price/amount, and if the price/amount differs, record their answer on the order.
Q: Is it possible to check sample products before bulk production?
A: There is physical evidence prior to bulk production. Check the measurements before approving the run, with your window.
Get a free quote on custom mailer packaging.
Provide product dimensions, maximum exterior dimensions for the carrier, and quantity tiers, and Empress Packaging will provide a quote for corrugated mailer packagings that include tolerance per line. To get a free quote, visit empresspackaging.com, contact query@empresspackaging.com, or call (888) 900-7629.
