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FedEx vs UPS Express Box Sizes: UPS Large Is 0.5 in Wider Than FedEx Large
The six boxes compared
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FedEx Express
FedEx Express Box Small (flat style)
Interior 12 3/8 × 10 7/8 × 1 1/2 in (314 × 276 × 38 mm)
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FedEx Express
FedEx Express Box Medium (flat style)
Interior 13 1/4 × 11 1/2 × 2 3/8 in (337 × 292 × 60 mm)
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FedEx Express
FedEx Express Box Large (flat style)
Interior 17 1/2 × 12 3/8 × 3 in (445 × 314 × 76 mm)
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UPS Express
UPS Express Box Small
Exterior 13 × 11 × 2 in (330 × 279 × 51 mm)
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UPS Express
UPS Express Box Medium
Exterior 15 × 11 × 3 in (381 × 279 × 76 mm)
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UPS Express
UPS Express Box Large
Exterior 18 × 13 × 3 in (457 × 330 × 76 mm)
The short answer
- FedEx SmallInterior 12 3/8 × 10 7/8 × 1 1/2 in (314 × 276 × 38 mm)
- FedEx MediumInterior 13 1/4 × 11 1/2 × 2 3/8 in (337 × 292 × 60 mm)
- FedEx LargeInterior 17 1/2 × 12 3/8 × 3 in (445 × 314 × 76 mm)
- UPS SmallExterior 13 × 11 × 2 in (330 × 279 × 51 mm)
- UPS MediumExterior 15 × 11 × 3 in (381 × 279 × 76 mm)
- UPS LargeExterior 18 × 13 × 3 in (457 × 330 × 76 mm)
See the sizes in AR (shown as boxes)
The four sizes as boxes at their published dimensions
Preparing 3D…
1 FedEx Small2 FedEx Medium3 FedEx Large4 UPS Medium
On a phone, the "View in your room (AR)" button places the boxes in your room. The boxes are locked to the published dimensions and cannot be resized. They show size only and are not 3D replicas of the products.
Drawn to the same scale
Dimensions side by side
| Box | W × D × H (in) | W × D × H (mm) | Dimension type |
|---|---|---|---|
| FedEx Small (flat style) | 12 3/8 × 10 7/8 × 1 1/2 | 314 × 276 × 38 | Interior |
| FedEx Medium (flat style) | 13 1/4 × 11 1/2 × 2 3/8 | 337 × 292 × 60 | Interior |
| FedEx Large (flat style) | 17 1/2 × 12 3/8 × 3 | 445 × 314 × 76 | Interior |
| UPS Express Box Small | 13 × 11 × 2 | 330 × 279 × 51 | Exterior |
| UPS Express Box Medium | 15 × 11 × 3 | 381 × 279 × 76 | Exterior |
| UPS Express Box Large | 18 × 13 × 3 | 457 × 330 × 76 | Exterior |
W × D × H order. Millimeters converted at 1 in = 25.4 mm and rounded to whole mm. FedEx publishes interior dimensions; UPS publishes exterior dimensions.
What the numbers mean
FedEx Express Boxes come in multiple styles per size tier. The flat-style boxes shown here (sometimes called "style 1") are the wide, shallow variants suitable for documents, clothing, and flat items. Each size also has a second deeper style: the Small style 2 is 11 1/4 × 8 3/4 × 2 5/8 in interior; the Medium style 2 is 11 1/4 × 8 3/4 × 4 3/8 in; the Large style 2 is 11 1/4 × 8 3/4 × 7 3/4 in. FedEx also offers an Extra Large box in two styles (roughly 12 × 11 × 11 in and 15 3/4 × 14 1/8 × 6 in interior).
UPS Express Boxes are available to UPS account holders at no charge and are intended for Express services (Next Day Air, 2nd Day Air). UPS publishes exterior dimensions; the interior is slightly smaller due to cardboard wall thickness.
Because FedEx publishes interior dimensions and UPS publishes exterior dimensions, a direct size comparison requires caution. The FedEx Large flat at 17 1/2 × 12 3/8 × 3 in interior and the UPS Large at 18 × 13 × 3 in exterior are close in height (both 3 in), with the UPS exterior measuring 0.5 in wider and 0.625 in deeper. Once you subtract UPS wall thickness (typically 1/8–1/4 in per side), the available interior space is nearly identical for the large sizes.
Both carriers require that you use their branded packaging when shipping in those boxes. FedEx Express Boxes ship on any FedEx Express service; UPS Express Boxes ship on UPS Express services. Neither carrier offers fixed-rate pricing based solely on box type in the same way USPS does — see the comparison section below.
FedEx and UPS express boxes vs USPS Flat Rate boxes
USPS Priority Mail Flat Rate boxes charge a single flat fee regardless of the package's weight (up to 70 lb) or destination within the US. FedEx and UPS do not offer a weight-and-distance-independent flat rate on their express packaging; their rates depend on weight, dimensions, zone, and service level.
| Box | W × D × H (in) | Dimension type | Carrier / pricing model |
|---|---|---|---|
| FedEx Large (flat) | 17 1/2 × 12 3/8 × 3 | Interior | FedEx Express (zone-based) |
| UPS Express Box Large | 18 × 13 × 3 | Exterior | UPS Express (zone-based) |
| USPS Medium Flat Rate Box 2 | 14 × 12 × 3 1/2 | Exterior | USPS Priority Mail (flat rate) |
| USPS Large Flat Rate Box | 12 1/4 × 12 × 6 | Exterior | USPS Priority Mail (flat rate) |
| USPS Medium Flat Rate Box 1 | 11 1/4 × 8 3/4 × 6 | Exterior | USPS Priority Mail (flat rate) |
USPS dimensions are exterior. FedEx dimensions are interior. UPS dimensions are exterior. See the USPS Flat Rate Box Sizes page for USPS interior vs exterior detail.
The USPS Medium Flat Rate Box 2 (exterior 14 × 12 × 3 1/2 in) is the closest USPS match in footprint to the FedEx Large flat and UPS Large. It is 3 1/2 in tall versus 3 in for both FedEx and UPS large boxes. The USPS Large Flat Rate Box (12 1/4 × 12 × 6 in) is shorter and wider than any flat-style FedEx or UPS express box.
Product links
13x11x2 shipping boxes on Amazon
14x12x3 shipping boxes on Amazon
18x12x3 shipping boxes on Amazon
FAQ
What are the dimensions of the FedEx Express boxes?
FedEx offers several Express Box sizes (interior dimensions). The Small flat box is 12 3/8 × 10 7/8 × 1 1/2 in (314 × 276 × 38 mm). The Medium flat box is 13 1/4 × 11 1/2 × 2 3/8 in (337 × 292 × 60 mm). The Large flat box is 17 1/2 × 12 3/8 × 3 in (445 × 314 × 76 mm). Each size also comes in a deeper second style.
What are the dimensions of the UPS Express boxes?
UPS Express Boxes come in three sizes (exterior dimensions). The Small is 13 × 11 × 2 in (330 × 279 × 51 mm). The Medium is 15 × 11 × 3 in (381 × 279 × 76 mm). The Large is 18 × 13 × 3 in (457 × 330 × 76 mm).
How do FedEx Express boxes compare to UPS Express boxes in size?
The FedEx Large flat box (17 1/2 × 12 3/8 × 3 in interior) and UPS Express Box Large (18 × 13 × 3 in exterior) share the same 3 in height. The UPS Large is 0.5 in wider and 0.625 in deeper. FedEx dimensions are interior; UPS dimensions are exterior, so the actual interior of the UPS Large is slightly smaller than its exterior.
How do FedEx and UPS express boxes compare to USPS Flat Rate boxes?
USPS Flat Rate boxes are about the same footprint as FedEx and UPS express boxes. The USPS Medium Flat Rate Box 1 exterior is 11 1/4 × 8 3/4 × 6 in — taller than all FedEx flat-style and UPS express boxes, which max out at 3 in height. The key difference is pricing: USPS Flat Rate charges a fixed fee regardless of distance or weight (up to 70 lb), while FedEx and UPS express boxes are for time-definite overnight or 2-day delivery.
See also: USPS Flat Rate Box Sizes: Interior vs Exterior — all four USPS Flat Rate boxes drawn to the same scale, with interior vs exterior dimensions.
Sources
- FedEx Express Box interior dimensions: FedEx.com, "Express Packaging". Direct site access restricted; dimensions confirmed via Atomix Logistics, "FedEx Box Sizes" (checked 2026-10-04) and corroborated by multiple third-party sources citing FedEx official packaging.
- UPS Express Box exterior dimensions: UPS.com, "Free Packaging". Site access restricted; dimensions confirmed via ParcelPath, "UPS Express Box" (checked 2026-10-04) and Easyship, "UPS Boxes" (checked 2026-10-04).
- USPS Flat Rate box dimensions: USPS.com Priority Mail page (checked 2026-09-29). See USPS Flat Rate Box Sizes for full detail.