Parcel and air
Shipping Girth Calculator
This calculator automatically treats the longest side as length and wraps girth around the other two dimensions. Girth = 2 x (width + height). Combined size = longest side + girth. It follows a cited USPS Postal Explorer source record captured 2026-08-12.
Find the longest side, girth, and combined length plus girth for any box orientation.
Enter shipment details
Planning result
90 in length plus girth
- Longest side
- 30 in
- Girth
- 60 in
- Wrapped dimensions
- 20 x 10 in
- Comparison
- No carrier limit selected
Use the longest side as length. Confirm the current limit and nonstandard fees for the exact carrier service.
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What this calculator returns
Use this shipping girth calculator to identify a package longest side, circumference around the other two sides, and combined length plus girth. It is intended for parcel shippers and fulfillment teams checking a carton against a current carrier or postal size rule before rating. The tool can compare with public USPS examples or a custom maximum.
How this is calculated
The calculator sorts the three entered dimensions from largest to smallest. The largest becomes length. Girth is twice the sum of the other two dimensions because a rectangular cross-section has two width sides and two height sides. Combined size is the longest side plus girth.
The selected maximum is used only as a comparison. It does not determine service eligibility or calculate a nonstandard, oversize, or additional handling fee. Current service rules remain authoritative.
Girth = 2 x (width + height). Combined size = longest side + girth.
Variable definitions
- L
- The longest outside package dimension, regardless of which input box it was entered in.
- W, H
- The two remaining outside dimensions around which girth is measured.
- G
- Girth, equal to 2 times the sum of W and H.
- Combined size
- Length plus girth, equal to L plus G.
Worked example
For a package measuring 30 by 20 by 10 inches, the 30 inch side is length. Girth is 2 times the sum of 20 and 10, which equals 60 inches. Length plus girth is 30 plus 60, or 90 inches.
Compared with a selected 108 inch maximum, the package is 18 inches under that numerical threshold. This comparison does not confirm eligibility because the exact postal product can also impose lower maximum dimensions, weight limits, shape rules, and nonstandard fees.
How to interpret the result
Measure the outside package at its greatest points after sealing. Bulges, handles, tubes, straps, and irregular packaging can change the dimensions used by the carrier.
A result below a selected limit only confirms the arithmetic comparison. Check the current service guide for the exact origin, destination, product, package type, weight, and fee structure before shipping.
What to measure
Use the outside packaged dimensions as the shipment will be tendered. Include pallets, skids, cartons, wrapping, overhang, and projections. Weigh the complete packaged unit, not only its contents. When pieces differ, create a separate row or calculation for each size and weight combination.
Assumptions and limitations
Service limits and nonstandard fees can differ. Verify the current carrier guide and the exact product used.
- It does not determine service eligibility, postage, zone, dimensional weight, or surcharges.
- It does not model cylindrical or irregular measurement rules beyond the entered rectangular dimensions.
- Public limits can change and lower limits may apply to a specific product or destination.
- It assumes the user measures the sealed package at its greatest outside points.
Rules and sources used
Frequently asked questions
Which side is package length?
For length-plus-girth rules, length is normally the longest outside side. The calculator identifies it automatically from the three entries.
How is girth measured?
For a rectangular package, add the two shorter dimensions and multiply by two. This represents the distance around the thickest cross-section.
Does being under 108 inches guarantee acceptance?
No. The exact service may have lower limits, weight restrictions, shape requirements, or nonstandard fees. Confirm the current service rules.
Is girth used for dimensional weight?
No. DIM weight uses package volume and a divisor. Girth is a separate size measure, although both can affect shipment acceptance or cost.