Key takeaways
- 1FedEx uses a DIM divisor of 139 for US shipments and applies dimensional weight to all shipments in customer packaging.
- 2Any fraction of an inch is rounded up to the next inch, a rule in effect since August 18, 2025.
- 3FedEx Ground Economy (formerly SmartPost) also divides by 139; parcels under 20 lb measuring 84 to 108 inches in length plus girth are billed at the 20 lb price.
- 4Soft packs over 18 × 13 × 5 inches count as non-standard packaging and cost $26.50 to $33.75 extra in the US.
- 5Oversize parcels (over 96 inches long, over 130 inches in length plus girth or over 17,280 cubic inches) have a 90 lb minimum billable weight.
The short answer
FedEx multiplies length, width and height in inches and divides by 139. Any fraction of an inch is rounded up first, and the result is rounded up to the next whole pound. FedEx charges for the greater of that dimensional weight and the actual weight. It applies to every shipment in your own box or mailer, and FedEx may apply it to its own packaging too. There is no size below which it stops, unlike USPS.
The rules below come from the FedEx Service Guide 2026 (effective January 5, 2026, updated September 11, 2026) and FedEx Ground Economy’s 2026 fees document, checked November 10, 2026. For the general method, see our guide to dimensional weight.
FedEx dimensional weight = L × W × H (each rounded up to a whole inch) ÷ 139, rounded up to the next whole pound
Worked examples
The table shows how FedEx bills common boxes. The price column uses the 2026 FedEx Home Delivery list rate to Zone 5 with the $6.45 residential surcharge, before the weekly fuel surcharge.
| Box (inches) | Actual weight | Dimensional weight | Billable weight |
|---|---|---|---|
| 10 × 8 × 6 | 3 lb | 3.45 lb | 4 lb |
| 14 × 10 × 6 | 2 lb | 6.04 lb | 7 lb |
| 12 × 12 × 12 | 5 lb | 12.43 lb | 13 lb (about $28.14 to Zone 5) |
| 18 × 14 × 10 | 6 lb | 18.13 lb | 19 lb (about $32.87 to Zone 5) |
| 24 × 18 × 12 | 15 lb | 37.29 lb | 38 lb |
FedEx Ground Economy (formerly SmartPost)
Ground Economy is FedEx’s low-cost residential service. It uses the same 139 divisor and rounds fractions of an inch up, with no 1 cubic foot exemption stated. Where the billable weight is over 70 lb, separate per-pound rates apply.
- Length plus girth = longest side + 2 × width + 2 × height. A 30 × 14 × 13 box is 30 + 28 + 26 = 84 inches, so a light item in it is billed at 20 lb.
| Rule | Applies when | Effect |
|---|---|---|
| Balloon pricing | Under 20 lb and 84 to 108 inches in length plus girth | Billed at the 20 lb price |
| Oversize | 108 to 130 inches in length plus girth | Oversize pricing applies |
| Non-Machinable | For example, two sides over 17 inches, or over 35 lb | $7.10 fee |
Soft packs, Additional Handling and Oversize
FedEx adds surcharges when a parcel is in soft packaging, is long or bulky, or is very large. These rules matter more for light, bulky items than the divisor does.
- The soft-pack rule catches many apparel sellers: a 20 × 14 inch poly mailer is over the limit even if it is light. Use a smaller mailer or a box.
| Charge | Applies when | Minimum billable weight | 2026 charge |
|---|---|---|---|
| Non-standard packaging | Not in a cardboard box (e.g. a poly mailer) and longer than 18 in, wider than 13 in or taller than 5 in | None | $26.50 to $33.75 |
| Additional Handling (dimensions) | Length + girth over 105 in, or over 10,368 in³ (from Jan 12, 2026) | 40 lb | $29.50 to $40.75 by zone |
| Oversize | Longest side over 96 in, length + girth over 130 in, over 17,280 in³, or over 110 lb | 90 lb | $255 to $330 by zone |
| Unauthorized package | Over 108 in long, over 165 in length + girth, or over 150 lb | 90 lb | $1,875 |
How to pay less with FedEx
The same habits that cut dimensional weight elsewhere work with FedEx, plus two FedEx-specific ones.
- Keep poly mailers within 18 × 13 × 5 inches, or switch to a small box.
- For light, bulky parcels on Ground Economy, keep length plus girth under 84 inches to avoid the 20 lb balloon price.
- Right-size boxes: at 139, a 5 lb item can go in a box of up to 695 cubic inches before dimensional weight takes over.
- Compare with USPS for parcels of 1 cubic foot or less, which USPS bills by actual weight.
- Ask about your divisor if you ship a lot; contract terms can differ from the published guide.
