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USPS Priority Mail: Flat Rate packages vs Flat Rate Green (dimensional)

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Welcome to the USPS Priority Mail guide to domestic service and package rates series. Learn how to use this guide.

In this guide, we compare specific USPS Priority Mail services: Flat Rate packages and Flat Rate Green, ShippingEasy's exclusive dimensional rates. Learn more about USPS Priority Mail.

Overview of service comparison:

With both Flat Rate packages and ShippingEasy's exclusive dimensional rates under Flat Rate Green, specific package restrictions apply.

In the case of Flat Rate packaging, the USPS requires using specially marked boxes. Contents must fit comfortably and packaging must be sealed without any bulging. Learn more about USPS domestic package dimensions. With Flat Rate packaging, one rate applies to the package type, regardless of distance (zone) or weight (up to 70 lbs).

In contrast, Flat Rate Green gives a little more flexibility in terms of dimensions, but lower weight limits. Shippers use their own packaging with the conditions that the package volume not exceed 0.50 cu ft, no dimension is longer than 18 inches, and the package weighs less than 20 lbs. Learn more about Flat Rate Green and dimensional pricing.

Flat Rate Green rates are based on package dimensions and distance (Zone). Learn more about Zones. By keeping packaging small, larger discounts are available. A tiered system is used to define package dimensions:

  • Tier 1: less than 0.10 cu ft
  • Tier 2: less than 0.20 cu ft
  • Tier 3: less than 0.30 cu ft
  • Tier 4: less than 0.40 cu ft
  • Tier 5: less than 0.50 cu ft

With Flat Rate Green, smaller packages ship for less than larger ones, when comparing similar destinations. Learn more about Flat Rate Green and dimensional pricing.

To compare the dimensions of Flat Rate packages with Flat Rate Green dimensions:

  • Flat Rate Envelopes measures approximately 0.07 cubic feet, the equivalent of Flat Rate Green Tier 1.
  • Flat Rate Small Box measures approximately 0.04 cubic feet, the equivalent of Flat Rate Green Tier 1.
  • Flat Rate Medium Box measures approximately 0.32 cubic feet, the equivalent of Flat Rate Green Tier 4.
  • Flat Rate Large Box measures approximately 0.46 cubic feet, the equivalent of Flat Rate Green Tier 5.

In general, Flat Rate packaging is best for the smallest of shipments, those traveling the furthest (higher Zone), or anything heavier than 20 lbs. The dimensional rates under Flat Rate Green are a better value than Flat Rate Medium and Large Boxes for most destinations.

It's also important to note that Flat Rate Green rates are only available to specific ShippingEasy subscription plans: Plus, Select, Premium, Enterprise. Learn more about plan differences. Any ShippingEasy subscriber can access Flat Rate package services.

 

Detailed service comparison:

The tables below provide a visual summary of when it's best to enter dimensions for Flat Rate Green or use Flat Rate packaging, based on weight, volume, and zone. Services which accommodate similar dimensions are compared:

TIP: to simplify the data, we use a color and letter code to indicate the best packaging. Please keep in mind that services listed are only the best value when your products will fit into the defined package dimensions. Use the legend below to read the following charts.
Legend for comparison tables
Priority Mail Service Code Packaging
Flat Rate M Medium or Small Boxes
All Envelopes
L All Boxes or Envelopes
Flat Rate Green 3 Tier 1, 2, or 3
4 Tier 1, 2, 3, or 4
5 Tier, 1, 2, 3, 4, or 5

Flat Rate Envelopes vs Flat Rate Green Tier 1:

Flat Rate Envelopes are the least expensive USPS Priority Mail service around. If you ship flat items that fit in these envelopes, it's your best option. Learn how to assign a carrier service to shipments.

Flat Rate Small Box vs Flat Rate Green Tier 1:

Flat Rate Small Box is less expensive than any dimensional rate. If you ship items that fit into these packages, it's your best option. Learn how to assign a carrier service to shipments.

Flat Rate Boxes vs Flat Rate Green Tier 2:

If your products won't fit into a Flat Rate Small box, but will fit within a volume less than 0.20 cubic feet, use a custom package. Flat Rate Green Tier 2 (0.20 cubic feet or less) pricing is less than Flat Rate Medium or Large Boxes across all destinations.

However, any packages weighing more than 20 lbs do not qualify for Flat Rate Green.

Learn how to assign a package and dimensions to your shipments.

Flat Rate Medium Box vs Flat Rate Green Tier 3:

Flat Rate Medium Box vs Flat Rate Green Tier 3

Prices by Zone: Commercial Plus
Weight Zones 1 & 2
Local
Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Zone 9
Up to
20 lbs
3 3 3 3 3 3 M M
Take away:

If your products fit in a Flat Rate Medium Box or box smaller than 0.30 cubic feet, base your decision on weight and destination.

For shipments weighing less than 20 lbs and traveling to Zones 1-7, use a custom package with volume less than 0.30 cubic feet.

When shipping heavier packages or anything across country to Zones 8 or 9, use the Flat Rate Medium Box.

Any packages weighing more than 20 lbs do not qualify for Flat Rate Green.

Learn how to assign a package and dimensions to your shipments.

 

Flat Rate Medium Box vs Flat Rate Green Tier 4:

Flat Rate Medium Box vs Flat Rate Green Tier 4

Prices by Zone: Commercial Plus
Weight Zones 1 & 2
Local
Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Zone 9
Up to
20 lbs
4 4 4 4 M M M M
Take away:

If your products fit in a Flat Rate Medium Box or box smaller than 0.40 cubic feet, base your decision on weight and destination.

For shipments weighing less than 20 lbs and traveling to Zones 1-5, use a custom package with volume less than 0.40 cubic feet.

When shipping heavier packages or anything to Zones 6-9, use the Flat Rate Medium Box.

Any packages weighing more than 20 lbs do not qualify for Flat Rate Green.

Learn how to assign a package and dimensions to your shipments.

Flat Rate Large Box vs Flat Rate Green Tiers 3 & 4:

Flat Rate Large Box vs Flat Rate Green Tiers 3 & 4

Prices by Zone: Commercial Plus
Weight Zones 1 & 2
Local
Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Zone 9
Up to
20 lbs
4 4 4 4 4 4 4 L
Take away:

If your products will not fit in a Flat Rate Medium Box, but will fit in a box smaller than 0.40 cubic feet, use a custom package with volume less than 0.40 cubic feet.

With two exceptions, products heavier than 20 lbs or traveling to Zone 9 should be shipped in the Flat Rate Large Box.

Any packages weighing more than 20 lbs do not qualify for Flat Rate Green.

Learn how to assign a package and dimensions to your shipments.

Flat Rate Large Box vs Flat Rate Green Tier 5:

Flat Rate Large Box vs Flat Rate Green Tier 5

Prices by Zone: Commercial Plus
Weight Zones 1 & 2
Local
Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Zone 9
Up to
20 lbs
5 5 5 5 5 5 L L
Take away:

If your products fit in a Flat Rate Large Box or box smaller than 0.50 cubic feet, base your decision on weight and destination.

For shipments weighing less than 20 lbs and traveling to Zones 1-7, use a custom package with volume less than 0.50 cubic feet.

When shipping heavier packages or anything to Zones 8 or 9, use the Flat Rate Large Box.

Any packages weighing more than 20 lbs do not qualify for Flat Rate Green.

Learn how to assign a package and dimensions to your shipments.

 

Continue comparing services:

Consider the conclusions that you've drawn about your shipments and whether or not Flat Rate packages or dimensional rates with Flat Rate Green are the better value. Then use this information to continuing comparing the best of the two with your other Priority Mail service options:

Flat Rate packages:

Are Flat Rate packages a good fit for your shipments? If so, take a look at these other rate comparison guides:

Flat Rate Green (dimensional):

Is Flat Rate Green a good fit for your shipments? If so, take a look at these other rate comparison guides:

 


Related articles:

Best of Rules: Assign a package and dimensions to my shipments
What is Flat Rate Green and does it relate to cubic pricing?
USPS Priority Mail: Guide to domestic service and package rates
Package Sizes and Dimensions: USPS Domestic
ShippingEasy's USPS Rate Tables

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