A few simple and basic rules of thumb for knowing about the most affordable ways to transport. If your parcel weighs:

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15.9 ounces or lower than that, then utilizing your parceling with the high-quality package would be the most affordable, always.

More than 1lb, but it is compatible with envelopes or Flat Rate boxes. These are the most affordable options.

You can’t keep more than 1lb and into those; using smaller boxes is most affordable. In this way, you can qualify for the Priority Mail Cubic.

Medium and Large boxes of Flat Rate will be a good option if the weight is over 20lbs. However, Rate Boxes that are regional may not be a great choice.

An advantage of Priority Mail Cubic is that you will be able to utilize your own parceling.

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However, USPS provides complimentary boxes that you can use along with Priority Mail Cubic:

Priority Mail Box -

1095 | Cubic Tier no. 4 | 12.5" x 3.125 x 15.375" (OD)

Shoe Box | Cubic Tier no. 4 | 7-3/8" x 5-1/4" x 14-7/8" (OD)

1092 | Cubic Tier no. 3 | 12.25" x 2.875" x 13.6875" (OD)

1097 | Cubic Tier no. 3 | 11.625" x 2.5" x 13.4375" (OD)

4 | Cubic Tier no. 2 | 7-1/4" x 7-1/4" x 6-1/2" (OD)

1096L | Cubic Tier no. 1 | 9-7/16" x 6-7/16" x 2-3/16" (OD)

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Learn more: How to Get Free Shipping Supplies from USPS, UPS, FedEx, and DHL

What is Priority Mail Cubic?

Priority Mail Cubic is a specialized service offered by the United States Postal Service (USPS) that prices packages based on their outer dimensions rather than weight. This unique pricing model can lead to significant savings, especially for small, dense packages weighing up to 20 pounds.

Key Features:

Dimension-based pricing: Rates determined by package size, not weight
Weight limit: Up to 20 pounds
Delivery timeframe: 1-3 business days
Insurance: $100 included for free
Tracking: Free package tracking included
Savings: Up to 90% off retail shipping rates

USPS Cubic Pricing Tiers

Priority Mail Cubic uses a tiered pricing system based on the package's volume. There are five tiers:

Tier 0.1: Up to 0.1 cubic feet
Tier 0.2: 0.101 to 0.2 cubic feet
Tier 0.3: 0.201 to 0.3 cubic feet
Tier 0.4: 0.301 to 0.4 cubic feet
Tier 0.5: 0.401 to 0.5 cubic feet

Calculating Your Package's Cubic Tier

For Boxes and Rigid Packages:

Measure the outer dimensions (length, width, height) in inches
Round each measurement down to the nearest quarter inch
Multiply length x width x height
Divide the result by 1728 (cubic inches in a cubic foot)
The result is your package's cubic feet measurement

Example: For a box measuring 12.3" x 9.5" x 3":

Round down to 12.25" x 9.5" x 3"
12.25 x 9.5 x 3 = 349.125
349.125 / 1728 = 0.202 cubic feet
This package falls into the 0.3 cubic feet pricing tier

Note: Maximum size for any single dimension is 18 inches

For Envelopes and Soft Packs:

Measure the length and width of the empty envelope
Round down to the nearest quarter inch
Add the length and width together
Use the total to determine the pricing tier:
- Tier 0.1: Up to 21"
- Tier 0.2: 21.01" to 27"
- Tier 0.3: 27.01" to 31"
- Tier 0.4: 31.01" to 34"
- Tier 0.5: 34.01" to 36"

Restrictions

Tubes and rolls are not eligible for Cubic pricing
Maximum combined length and girth is 84 inches

Benefits of Using Priority Mail Cubic

Cost savings: Cheaper than weight-based pricing for small, heavy items
Predictable pricing: Easy to calculate shipping costs based on box dimensions
Fast delivery: 1-3 business day delivery to any US address, including PO boxes
Free tracking: Monitor shipments at no extra cost
Included insurance: $100 of coverage with every shipment
No surcharges: Residential and fuel surcharges included in the price

Tips for Maximizing Savings

Optimize packaging: Use the smallest box possible that safely fits your items
Consider breaking up large orders: Sometimes shipping in multiple smaller boxes can be cheaper
Use cubic feet calculators: Online tools can help quickly determine your package's tier
Compare rates: Always compare Cubic rates with other shipping methods
Use Commercial Pricing: Accessing Commercial Pricing rates can lead to even more savings

2024 USPS Priority Mail Cubic Rates

[Insert current rate table here]

Accessing Priority Mail Cubic Rates

Priority Mail Cubic isn't available at regular Post Office counters. However, many online shipping platforms and 3PL providers offer access to these rates. By partnering with a fulfillment provider, you can easily access these discounted rates and streamline your shipping process. For small-scale sellers not yet ready for a 3PL, Pirate Ship offers free access to USPS Priority Mail Cubic rates with no monthly fees or minimums.

The Cheapest Ways to Ship With USPS®

A few simple and basic rules of thumb for knowing about the most affordable ways to transport.