How the calculator works
You can enter the package dimensions in any order. The calculator identifies the longest side as length, then treats the other two sides as width and height for the girth calculation.
Girth = 2 × width + 2 × height
Length + girth = length + girth
Example
For a 20 × 12 × 8 inch box, length is 20 inches. Girth is 2 × 12 + 2 × 8 = 40 inches. Length plus girth is therefore 60 inches.
Why carriers use length + girth
Some parcel services use length plus girth in maximum-size rules, oversize definitions, or surcharges. It is a size measurement, not a weight calculation. Dimensional weight is separate and is based on package volume.
Measure the finished package
Use the outside dimensions of the packed parcel. Bulges, protruding contents, or irregular shapes can change how a carrier measures a shipment. Carrier rounding and irregular-package rules vary.
Check the current carrier rule
As of August 2026, UPS Canada states a general small-package maximum of 165 inches (419 cm) in combined length and girth and defines the formula as length + 2 × width + 2 × height, while USPS publishes service-specific size limits. These limits can change and can differ by country or service.