What Is a 4×6 Shipping Label in mm? | Exact Dimensions Explained

A 4×6 shipping label measures 101.6 mm × 152.4 mm in precise metric conversion, though most manufacturers round it to 100 mm × 150 mm for simplicity.

A 4×6 shipping label in mm has two answers: the exact metric conversion of 101.6 × 152.4 mm, and the rounded industry standard of 100 × 150 mm used by most thermal label suppliers worldwide. The four-by-six-inch size is the default shipping label for USPS, UPS, FedEx, DHL, and Amazon, and knowing both figures prevents confusion when buying labels or configuring software that lists sizes in millimeters.

What Are the Exact Dimensions of a 4×6 Shipping Label?

The precise imperial measurement is 4 inches wide by 6 inches long. Converting those inches to millimeters yields 101.6 mm × 152.4 mm — the mathematically exact equivalent. This is the figure you will see in printer driver settings and on spec sheets from brands like MUNBYN and Betckey that list both units.

A 4×6 Shipping Label in mm: The Difference Between Exact and Rounded

Shipping platforms and thermal label suppliers frequently list the size as 100 mm × 150 mm instead of the exact 101.6 × 152.4. That is not a mistake — it is a deliberate rounding that has become the de-facto standard in e-commerce. The two sizes are functionally identical on any direct thermal printer designed for 4×6 labels, and rolls labeled 100 × 150 mm fit the same printers as rolls labeled 101.6 × 152.4 mm. Rollo’s support documentation confirms that many companies manufacture rolls slightly smaller than the exact conversion but market them as “4×6” because the barcode and address area still fit comfortably within the printable zone.

Which Carriers and Platforms Accept 4×6 Labels?

Every major carrier and marketplace supports the 4×6 format. Below is a breakdown of who accepts it and the few exceptions you need to know.

Amazon’s own guidelines state that the 4×6 size ensures barcode scanners at fulfillment centers read labels on the first pass. Smaller sizes like 4×4 increase misreads and can delay shipments.

What Type of Printer Do You Need for 4×6 Labels?

The only printer that works with 4×6 thermal labels is a direct thermal printer. Standard desktop inkjet or laser printers cannot feed individual sticky label rolls — they require 8.5×11 inch sheets with one label per page. Direct thermal printers use heat-sensitive paper and do not need ink or toner refills.

When buying labels, check the core diameter. Most thermal printers use a 1-inch (25 mm) core. Three-inch core rolls exist but are uncommon and may not fit your printer. Our tested roundup of the best 4×6 shipping labels covers rolls that fit standard 1-inch cores and work with the most popular thermal printers.

How to Set Up 4×6 Label Format in Pirate Ship or Shopify

Configuring the label size correctly before buying postage prevents wasted labels and reprints. The steps are nearly identical on most shipping platforms.

1. Navigate to the Ship page. If you are on Basic Shipping view, click Switch to Advanced Shipping to see all label options.
2. Scroll to the Label Preferences panel on the right side of the screen.
3. Click Change next to the label size dropdown.
4. Select 4 by 6 (Thermal) for direct thermal printers, or 8 by 11 (Laser) for sheet-fed printers.
5. Optionally switch the file format between PDF and PNG.
6. Set the format before purchasing the label. Changing it after payment is not possible.

After you configure the size and purchase the label, the printer will produce a 4×6 output with the barcode and address area fitting the standard thermal label dimensions.

Common Mistakes When Using 4×6 Labels

Three errors cause most of the frustration with shipping labels. The first is assuming 100 × 150 mm labels will not work in a printer expecting 101.6 × 152.4 mm — they are interchangeable in practice. The third is printing a 4×6 thermal label for a carrier like TNT or Hong Kong Post that explicitly requires A4 paper. One quick check of the carrier’s label guidelines before printing saves a wasted label and a delayed package.

Shipping Label Dimensions at a Glance