FedEx rounds every fraction of an inch up. Here is what it costs.
Since August 18, 2025 FedEx rounds any fraction of an inch up to the next whole inch. See what that does to a 12-inch box and how to get back under the line.
On August 18, 2025, FedEx changed how it rounds package dimensions. Before, a side was rounded to the nearest whole inch, so 12.4 inches billed as 12. Now any fraction of an inch rounds up. A side that measures 12.1 inches bills as 13.
That sounds small. It is not, because the three sides are multiplied together.
What it does to a 12-inch box
Boxes are sold by their inside size. A box listed as 12 × 12 × 12 is a little bigger on the outside, because of the cardboard walls and the flaps: usually around 12.3 inches or more per side. The scanner measures the outside.
| Billed size | Cubic inches | Dim weight at 139 | |
|---|---|---|---|
| Old rule (nearest inch) | 12 × 12 × 12 | 1,728 | 13 lb |
| New rule (always up) | 13 × 13 × 13 | 2,197 | 16 lb |
Same box, three more billed pounds. On 2026 FedEx Ground list rates that is:
- Zone 5: $21.69 at 13 lb, $23.41 at 16 lb. $1.72 more per package.
- Zone 8: $31.27 at 13 lb, $37.16 at 16 lb. $5.89 more per package.
Those are before fuel, which is charged as a percentage on top and makes the gap wider.
How to get back under the line
Measure the outside, not the catalog size. Tape a box shut the way you ship it and measure the widest point of each side. That is the number that matters.
Pick boxes that land on or just under a whole inch. A box with an outside of 11.9 inches bills as 12. A box with an outside of 12.1 bills as 13. If your supplier lists outside dimensions, shop by those.
Stop the bulge. An overfilled box bows out in the middle, and the scanner reads the widest point. A box that should measure 12.0 can read 12.4. Do not overpack, and tape flaps flat.
Cut the box down. If the contents do not fill the height, score the corners and fold the flaps lower. Taking a 13-inch-tall package to 10 inches removes almost a quarter of its volume.
Only fix what matters. If a package is billed on its actual weight, not its dim weight, trimming an inch saves nothing. Check first.
See what one inch is worth for your box
In the free calculator, enter your box's real outside measurements. If a side is sitting just over a whole inch, it tells you exactly how much you would save by getting under it.
Rates quoted here are FedEx 2026 standard list rates, effective January 5, 2026, for packages billed at dim weight with the standard 139 divisor.