USPS cubic rates are ideal for small, heavy packages because the pricing is based on the volume of the package and the zone instead of the weight.
In order to qualify by USPS cubic rates, each mail piece:
Must measure .50 cubic feet or less
Weigh 20 pounds or less
The longest dimension may not exceed 18 inches
May not be rolls or tubes
Two different methods exist for determining the cubic tier:
Rectangular and Nonrectangular Parcels
Padded Envelopes, Polybags and Soft Packs
Rectangular and Nonrectangular Parcels
To calculate cubic weight:
Measure the Length, Width and Height in inches rounded down to the nearest 0.25 inch.
Multiply the Length * Width * Height (LxWxH) and then divide by 1728.
If the result is between 0.1 and 0.5, your package qualifies for Cubic Weight.
Anything higher than 0.5 would use the regular weight or dim calculation and would not qualify for cubic pricing.
Example:
Actual package measurements: 6.125" x 5.875" x 6.375"
Rounded down to the nearest 0.25 inch: 6” x 5.75” x 6.25”
6” x 5.75” x 6.25” divided by 1728 = .125 cubic feet which qualifies for Tier 2 pricing
USPS Cubic Pricing Tiers
Tier 1: Mailpieces measuring up to .10 cubic foot
Tier 2: Mailpieces measuring more than .10 up to .20 cubic foot
Tier 3: Mailpieces measuring more than .20 up to .30 cubic foot
Tier 4: Mailpieces measuring more than .30 up to .40 cubic foot
Tier 5: Mailpieces measuring more than .40 up to .50 cubic foot
Tier 6*: Mailpieces measuring more than .50 up to .60 cubic foot
Tier 7*: Mailpieces measuring more than .60 up to .70 cubic foot
Tier 8*: Mailpieces measuring more than .70 up to .80 cubic foot
Tier 9*: Mailpieces measuring more than .80 up to .90 cubic foot
Tier 10*: Mailpieces measuring more than .90 up to 1.00 cubic foot
* USPS Ground Advantage only.
Padded Envelopes, Polybags and Soft Packs
USPS Soft Pack Pricing is a subset of the Cubic Pricing for Priority and Ground Advantage packages shipped inside of bags/envelopes/sacks, even if boxes are contained inside the bags. Softpack tiers are assigned using only two dimensions.
In order to qualify by USPS Soft Pack cubic rates each mailpiece:
Must weigh 20 pounds or less
Can not be presented folded
Can not exceed 18”x18”(not including the lip)
To calculate Soft Pack cubic weight:
Measure your empty envelope before you put anything in it. Must be flat and not rolled up.
Measure the Length and Width in inches rounded down to the nearest 0.25 inch.
Add the two measurements together.
The sum determines the cubic price tier.
Example:
Actual package measurements 9" x 12"
9” + 12” = 21” qualifies for Tier 1 pricing
Priority Mail Cubic Pricing Tiers for Soft Pack and Padded Envelopes
Tier 1: Envelopes with a Length plus Width measuring from 0" up to 21"
Tier 2: Envelopes with a Length plus Width measuring more than 21" up to 27"
Tier 3: Envelopes with a Length plus Width measuring more than 27" up to 31"
Tier 4: Envelopes with a Length plus Width measuring more than 31" up to 34"
Tier 5: Envelopes with a Length plus Width measuring more than 34" up to 36"
USPS Ground Advantage Cubic Pricing Tiers for Soft Pack and Padded Envelopes
Tier 1: Envelopes with a Length plus Width measuring from 0" up to 16"
Tier 2: Envelopes with a Length plus Width measuring more than 16" up to 21"
Tier 3: Envelopes with a Length plus Width measuring more than 21" up to 24"
Tier 4: Envelopes with a Length plus Width measuring more than 24" up to 26"
Tier 5: Envelopes with a Length plus Width measuring more than 26" up to 28"
Tier 6: Envelopes with a Length plus Width measuring more than 28" up to 30"
Tier 7: Envelopes with a Length plus Width measuring more than 30" up to 32"
Tier 8: Envelopes with a Length plus Width measuring more than 32" up to 34"
Tier 9: Envelopes with a Length plus Width measuring more than 34" up to 35"
Tier 10: Envelopes with a Length plus Width measuring more than 35" up to 36"