How to measure a package for shipping
Carriers re-measure a large share of the packages they handle, often with automated scanners, and bill you the difference if your declared size was wrong. Measuring the same way they do avoids those adjustment charges.
Measure the outside, as shipped
Always measure the sealed, packed box. Carriers measure the outside of what they receive, including bulges from overfilling, handles and labels that stick out. A box that was 12 inches flat but bulges to 12¾ will be treated as 13.
Which side is length?
For shipping, length is always the longest side, whatever the box's orientation. Width and height are the other two sides. This matters because some limits and surcharges look at the longest side on its own, and girth is calculated from the other two.
Step by step
- Place the box on a flat surface. Use a rigid tape measure, not a cloth one.
- Measure the longest side. That's the length.
- Measure the other two sides. These are width and height.
- Round up. Carriers round to whole inches. If a side is 14⅜, call it 15 for estimates.
- Weigh it. Use a calibrated scale and round up to the next pound.
Length plus girth
Girth is the distance around the package at its thickest point: twice the width plus twice the height. Length plus girth is used for size limits. A 30 × 20 × 15 inch box has a girth of 70 and a length plus girth of 100 inches.
Commonly published limits are 165 inches length plus girth for UPS and FedEx, and 108 inches for most USPS services (130 for Ground Advantage). Packages approaching these limits may also trigger large-package or additional-handling surcharges.
Irregular packages
For tubes, bags and odd shapes, carriers measure the smallest rectangle the item fits inside. A mailing tube 36 inches long and 4 inches across is measured as 36 × 4 × 4. Poly mailers are measured at their fullest point when packed.
How to avoid adjustment charges
- Record the outside size of each box you use, measured when packed, and use those numbers in your shipping software.
- Don't overfill. A box that bulges is a bigger box.
- Recheck when a supplier changes your boxes; a different board or manufacturer can change outside sizes.
- Audit invoices for adjustments. Repeated corrections on one product point to a measurement or packing problem.
Why it matters for price
Most parcel prices depend on billable weight, which is the higher of actual and dimensional weight. Since dimensional weight comes from the three measurements, an extra inch on each side of a mid-size box can add several pounds.