About this calculator
Estimate a USPS Cubic tier and package-rule eligibility for the selected commercial program. Boxes use quarter-inch measurement rounding and volume tiers; soft packs use a separate flat-size table.
Inputs
How to use this calculator
Package group
- Cubic package formatRolls and tubes are outside the cubic formats handled here.
- Box length (in)Outer tendered dimensions including packaging and projections. This input is shown when Cubic package format is set to Rectangular box.
- Box width (in)Outer tendered dimensions including packaging and projections. This input is shown when Cubic package format is set to Rectangular box.
- Box height (in)Outer tendered dimensions including packaging and projections. This input is shown when Cubic package format is set to Rectangular box.
- Flat package length (in)Outer tendered dimensions including packaging and projections. This input is shown when Cubic package format is set to Soft pack or padded envelope.
- Flat package width (in)Outer tendered dimensions including packaging and projections. This input is shown when Cubic package format is set to Soft pack or padded envelope.
- Longest packed side (in)Outer tendered dimensions including packaging and projections. This input is shown when Cubic package format is set to Soft pack or padded envelope.
- Gross package weight (lb)Gross weight including all packaging and pallet tare.
- Identical piecesPositive whole count. Add a row for different dimensions or per-piece weight.
Shared inputs
- USPS Cubic programChoose the dated USPS program used for the package.
- Eligible commercial postage access confirmed?This tool checks package rules only; it cannot grant postage-program eligibility.
Enter the shipment or scenario values, then select Calculate result.
Method
Formula and variables
For boxes, round each outer dimension down to the nearest ¼ in, calculate cubic feet = L × W × H ÷ 1,728, then round up to the next 0.1 ft³ tier. Ground Advantage Commercial allows box tiers through 1.0 ft³; Priority Mail Cubic through 0.5 ft³. For soft packs, round flat length and width down to ¼ in, add them, then map ≤21/27/31/34/36 in to tiers 0.1/0.2/0.3/0.4/0.5 ft³. Both formats require ≤20 lb and a longest side ≤22 in; soft packs also require length + width ≤36 in.
- Cubic package format
- Rolls and tubes are outside the cubic formats handled here.
- Box length (in)
- Outer tendered dimensions including packaging and projections. This input is shown when Cubic package format is set to Rectangular box.
- Box width (in)
- Outer tendered dimensions including packaging and projections. This input is shown when Cubic package format is set to Rectangular box.
- Box height (in)
- Outer tendered dimensions including packaging and projections. This input is shown when Cubic package format is set to Rectangular box.
- Flat package length (in)
- Outer tendered dimensions including packaging and projections. This input is shown when Cubic package format is set to Soft pack or padded envelope.
- Flat package width (in)
- Outer tendered dimensions including packaging and projections. This input is shown when Cubic package format is set to Soft pack or padded envelope.
- Longest packed side (in)
- Outer tendered dimensions including packaging and projections. This input is shown when Cubic package format is set to Soft pack or padded envelope.
- Gross package weight (lb)
- Gross weight including all packaging and pallet tare.
- Identical pieces
- Positive whole count. Add a row for different dimensions or per-piece weight.
- USPS Cubic program
- Choose the dated USPS program used for the package.
- Eligible commercial postage access confirmed?
- This tool checks package rules only; it cannot grant postage-program eligibility.
Interpret the result
A tier is not a postage quote. The program cap, measured longest side, weight and confirmation of commercial access can exclude a package even when its tier is calculable.
Outputs: Cubic tier eligibility and package-specific exclusions
Eligibility and tier only, not a postage quote. Commercial account access, destination zone, rate, packaging construction and every mailing exception are not validated. Ground Advantage and Priority Mail have different box-volume caps. Tubes, rolls and other non-cubic shapes are excluded. Recheck the applicable Domestic Mail Manual after USPS updates.
Worked example
Check the arithmetic
This example uses the starting values shown above. The arithmetic below is calculated independently of the interactive result.
Work through the calculation
- The 12 × 10 × 8 in box is unchanged by quarter-inch rounding. Cube = 960 ÷ 1,728 = 0.5555556 ft³.
- Round up to the next 0.1 ft³ tier: 0.6 ft³.
- At 6 lb, with a 12 in longest side and confirmed commercial access, the default Ground Advantage Cubic screen accepts 1 piece.
Compare the displayed result
Expected displayed result: 1 piece qualifies for Cubic
FAQs
Why does the same box qualify for one Cubic program but not another?
The modeled box-volume caps differ: Ground Advantage Cubic allows up to 1.0 ft³ and Priority Mail Cubic up to 0.5 ft³. Other eligibility checks still apply.
Sources
These references support the methods or rules used on this page. Check the version effective for your shipment date and any applicable carrier terms or item-specific provisions.
Example inputs and options
Starting values are examples unless a field identifies a dated rule. Unit selectors convert only fields marked for conversion. Rates and model options keep the units and basis shown in their labels.
- Cubic package format
- Example: Rectangular boxOptions: Rectangular box; Soft pack or padded envelope
- Box length (in)
- Example: 12
- Box width (in)
- Example: 10
- Box height (in)
- Example: 8
- Flat package length (in)
- Example: 18
- Flat package width (in)
- Example: 12
- Longest packed side (in)
- Example: 18
- Gross package weight (lb)
- Example: 6
- Identical pieces
- Example: 1
- USPS Cubic program
- Example: Ground Advantage Cubic (Commercial)Options: Ground Advantage Cubic (Commercial); Priority Mail Cubic
- Eligible commercial postage access confirmed?
- Example: YesOptions: No / not confirmed; Yes