Label Sizes

For almost all carriers they handle 4X6 labels well. However, some of the carriers have some extra sizes you can use or support a different size for some reason.

Here are the labels sizes that may be different:

• UPS results in a 4x7 if you don't override, but if you print it as 4x6 it's usually ok since the last inch is just a blank space for notes anyway. If you ask for 4x7 or 4x8, you get a label back, but both are just a 4x6 with 1 or 2 inches of blank space.
• DHL Express supports the following label_sizes: 4x7, 8.5x11, 4x6 and 4x8
• USPS - Please see this article. 
• FedEx supports 4x6 and 4x8
• Lasership supports 4x6 and 4x8 supported only for ZPL format
• Ontrac supports 4x6 and 4x8 supported only for ZPL format format

You have the ability to select different label formats through EasyPost, and these each have a pre-set size to them if you do not override. If you specify a format without size, the result will vary somewhat. For example, if you specify PDF but not a size, you'll end up with a 4x6 label embedded in an 8.5x11 sized PDF.

Size By Type:

• 1. PDF: 8.5x11
• 2. EPL: 4x5
• 3. ZPL: 4x5
• 4. PNG: 4x6

To use the size type you can utilize the shipment option label_format. See example below:

"options": {
  "label_format": "PDF"
}