USPS Dimensional Weight Changed to 139: What It Costs Your Parcels

For years, USPS was the forgiving carrier for light, bulky parcels. On July 12, 2026 that changed: USPS cut its dimensional weight divisor from 166 to 139, the figure UPS and FedEx already used, and started rounding every measurement up to the next whole inch. If you ship pillows, apparel, packaging-heavy products or anything light in a big box, your USPS postage likely went up.

What changed

	Before July 12, 2026	From July 12, 2026
USPS divisor	166	139
Rounding of dimensions	To the nearest inch	Up to the next whole inch
Applies to	Parcels over 1 cubic foot	Parcels over 1 cubic foot (unchanged)
UPS and FedEx divisor	139	139 (unchanged)

A lower divisor produces a higher dimensional weight. Dividing by 139 instead of 166 raises the DIM weight of the same box by about 19%.

How billable weight is worked out

1. Measure length, width and height, and round each up to the next whole inch.
2. Multiply them for the volume in cubic inches.
3. Divide by 139 and round up to the next pound.
4. Compare with the actual weight. You pay for whichever is higher.

USPS skips steps 1 to 3 for parcels of one cubic foot (1,728 cubic inches) or less, which are charged on actual weight. UPS and FedEx apply dimensional weight to every parcel.

Billable weight for common box sizes

Box (inches)	Volume	Actual weight	UPS / FedEx	USPS now	USPS before
12 × 10 × 8	960 in³	3 lb	7 lb	3 lb	3 lb
14 × 12 × 10	1,680 in³	5 lb	13 lb	5 lb	5 lb
16 × 12 × 12	2,304 in³	4 lb	17 lb	17 lb	14 lb
18 × 14 × 10	2,520 in³	6 lb	19 lb	19 lb	16 lb
20 × 16 × 12	3,840 in³	8 lb	28 lb	28 lb	24 lb
24 × 18 × 12	5,184 in³	10 lb	38 lb	38 lb	32 lb

The first two rows show where USPS still has an edge: boxes up to one cubic foot are billed on actual weight at USPS, while UPS and FedEx bill a 14 × 12 × 10 box at 13 lb even if it weighs 5. Above one cubic foot, USPS now bills exactly what UPS and FedEx do.

Who is affected most

• Light, bulky products: bedding, apparel in rigid boxes, lampshades, plush toys and foam-packed items, where dimensional weight is several times the actual weight.
• Sellers who chose USPS for big boxes: the old 166 divisor made USPS the cheapest option for many parcels just over a cubic foot. That advantage is gone; compare rates again.
• Anyone using standard box sizes: rounding up means a box measured at 16.2 inches is now billed as 17.

Five ways to cut the cost

Use the smallest box that protects the item. Taking one inch off each side of an 18 × 14 × 10 box (to 17 × 13 × 9) drops its billable weight from 19 lb to 15 lb.

Stay under one cubic foot for USPS. A box of 1,728 cubic inches or less (for example 12 × 12 × 12) is still billed on actual weight at USPS.

Switch to poly mailers for soft goods. Clothing and textiles that don't need a rigid box can often go in a mailer with far less volume.

Measure accurately. Round each side up yourself before you buy labels, so your quoted rate matches the carrier's bill and you avoid adjustment charges.

Ask about your divisor. High-volume shippers can sometimes negotiate a higher divisor in their contract. Enter it as a custom divisor in the calculator to see the difference.

Check your own boxes

Enter any box size and weight in the dimensional weight calculator. It shows the billable weight at UPS and FedEx, at USPS under the new and old rules, and for metric international shipments.