Dimensional Weight Calculator and Carrier Divisors
For anyone shipping a parcel who wants to know the weight the carrier will actually bill. Enter the outside box dimensions and the real weight to see the dimensional weight under each common divisor.
Dimensional (DIM) weight is length × width × height ÷ divisor. In the US, UPS, FedEx and (since July 12, 2026) USPS all use a divisor of 139 with inches and pounds, so a 12 × 12 × 12 in box has a DIM weight of 1,728 ÷ 139 = 12.4, billed as 13 lb. With centimeters and kilograms the usual divisor is 5,000 (express) or 6,000 (air freight and many postal services). The carrier charges whichever is higher, the DIM weight or the actual weight.
- UPS / FedEx / USPS
- ÷ 139 (in, lb)
- Express, metric
- ÷ 5,000 (cm, kg)
- Air freight, metric
- ÷ 6,000 (cm, kg)
- USPS applies above
- 1 cu ft (1,728 in³)
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Dimensional weight calculator
Use the outside dimensions of the packed box, measured at the widest point of any bulge. The calculator rounds each dimension up to the next whole inch or centimeter, as US carriers now do, then rounds the result up to the next whole pound (or half kilogram for metric divisors).
Dimensional weight and billable weight
The default example, a 16 × 12 × 12 in box holding 6 lb, has a DIM weight of 16.6 lb and is billed at 17 lb by UPS and FedEx. Switch the size unit to centimeters and the weight to kilograms to work with a metric divisor; the calculator converts as needed.
The dimensional weight formula
Carriers turn a box's volume into a weight with one division, then bill the larger of the two weights. The steps are the same for every carrier; only the divisor and the rounding change.
- Measure the outside of the packed box. Length is the longest side. Include bulges, handles and anything strapped on.
- Round each dimension up to a whole number. 12.2 in counts as 13 in. UPS and FedEx round every fraction up (from August 2025), and USPS does too from July 12, 2026.
- Multiply length × width × height to get cubic inches or cubic centimeters.
- Divide by the divisor. 139 for inches and pounds at UPS, FedEx and USPS; 5,000 or 6,000 for centimeters and kilograms.
- Round the result up to the next whole pound (US) or, for most metric express services, the next 0.5 kg.
- Compare with the actual weight, also rounded up. The higher number is the billable weight used for the rate.
Worked example in metric: a 40 × 30 × 20 cm carton holds 24,000 cm³. At ÷ 5,000 its volumetric weight is 4.8 kg (billed as 5 kg); at ÷ 6,000 it is 4.0 kg. If the contents weigh 3 kg, you pay for 5 kg with a 5,000-divisor courier and 4 kg with a 6,000-divisor service.
DIM divisors by carrier (2026)
| Carrier and service | Inches / pounds | cm / kg | When it applies |
|---|---|---|---|
| UPS (daily rates, account holders) | 139 | 5,000 | All packages |
| UPS (retail rates, The UPS Store) | 166 | 6,000 | All packages |
| FedEx Express and Ground | 139 | 5,000 | All packages |
| USPS Priority Mail, Priority Mail Express, Ground Advantage, Parcel Select | 139 (166 before July 12, 2026) | n/a | Only boxes over 1 cu ft (1,728 cu in) |
| DHL Express | 139 equivalent | 5,000 | All shipments |
| Air freight (IATA convention) | 166 equivalent | 6,000 | Consolidated air cargo |
The pairs are the same rule in two unit systems: 139 in³/lb equals 5,022 cm³/kg, and 166 in³/lb equals 5,997 cm³/kg. Negotiated contracts often carry a higher divisor (166 or more), which lowers the DIM weight. Divisors and rounding rules change, so confirm the current figure in the carrier's service guide before quoting a customer.
Older calculators and spreadsheets still use 166 for USPS. From July 12, 2026 the divisor is 139 and every fractional inch rounds up, so a USPS box over 1 cubic foot now bills about 19% heavier than it did under the old rule.
Dimensional weight of common box sizes
These are stock box sizes measured outside, in whole inches. The USPS column shows whether the box is large enough for USPS to apply dimensional weight at all.
| Box (in) | Box (cm) | Volume | DIM weight ÷ 139 | DIM weight ÷ 166 | USPS DIM applies? |
|---|---|---|---|---|---|
| 6 × 6 × 6 | 15.2 × 15.2 × 15.2 | 216 cu in (3.5 L) | 2 lb | 2 lb | No |
| 10 × 8 × 6 | 25.4 × 20.3 × 15.2 | 480 cu in (7.9 L) | 4 lb | 3 lb | No |
| 12 × 9 × 6 | 30.5 × 22.9 × 15.2 | 648 cu in (10.6 L) | 5 lb | 4 lb | No |
| 12 × 12 × 8 | 30.5 × 30.5 × 20.3 | 1,152 cu in (18.9 L) | 9 lb | 7 lb | No |
| 12 × 12 × 12 | 30.5 × 30.5 × 30.5 | 1,728 cu in (28.3 L) | 13 lb | 11 lb | No (exactly 1 cu ft) |
| 16 × 12 × 12 | 40.6 × 30.5 × 30.5 | 2,304 cu in (37.8 L) | 17 lb | 14 lb | Yes |
| 14 × 14 × 14 | 35.6 × 35.6 × 35.6 | 2,744 cu in (45.0 L) | 20 lb | 17 lb | Yes |
| 18 × 14 × 12 | 45.7 × 35.6 × 30.5 | 3,024 cu in (49.6 L) | 22 lb | 19 lb | Yes |
| 18 × 18 × 18 | 45.7 × 45.7 × 45.7 | 5,832 cu in (95.6 L) | 42 lb | 36 lb | Yes |
| 20 × 20 × 20 | 50.8 × 50.8 × 50.8 | 8,000 cu in (131 L) | 58 lb | 49 lb | Yes |
| 24 × 18 × 18 | 61.0 × 45.7 × 45.7 | 7,776 cu in (127 L) | 56 lb | 47 lb | Yes |
| 24 × 24 × 24 | 61.0 × 61.0 × 61.0 | 13,824 cu in (227 L) | 100 lb | 84 lb | Yes |
Read the DIM column as a break-even point: if the packed contents weigh more than that, you pay for actual weight and the box size does not matter. A 12 × 9 × 6 box of books (8 lb) ships at 8 lb; the same box of T-shirts (2 lb) ships at 5 lb with UPS or FedEx. For inside dimensions and board strength of these boxes, see the shipping box size guide.
Which items get billed by size
Dimensional weight wins whenever the package is less dense than the divisor implies. At ÷ 139 that threshold is 12.4 lb per cubic foot (199 kg/m³); at ÷ 166 it is 10.4 lb per cubic foot (167 kg/m³). Anything lighter than that per unit of box volume is billed by its dimensions.
| Parcel | Box | Actual weight | DIM weight | Billed on |
|---|---|---|---|---|
| Queen comforter | 18 × 14 × 12 in | 7 lb | 22 lb | Size |
| Pair of running shoes in shoebox | 14 × 10 × 6 in | 3 lb | 7 lb | Size |
| Table lamp with shade | 20 × 20 × 20 in | 9 lb | 58 lb | Size |
| Hardcover books (12) | 12 × 12 × 8 in | 22 lb | 9 lb | Weight |
| Pair of 10 lb dumbbells | 10 × 8 × 6 in | 21 lb | 4 lb | Weight |
Bedding, lampshades, plush toys, pillows, foam and anything shipped with lots of void fill land in the first group. Books, tools, liquids, weights and canned food land in the second. A 14 × 10 × 6 shoebox outer carton is 840 cu in, so 840 ÷ 139 = 6.04, which rounds up to 7 lb: a small overshoot past a whole number costs a full pound. Typical shoebox sizes are in the shoe box guide.
How to lower dimensional weight
- Choose the smallest box that clears the item plus padding. Going from 18 × 18 × 18 to 16 × 12 × 12 cuts the DIM weight from 42 lb to 17 lb.
- Watch the whole-inch edge. Because fractions round up, a box measuring 12.1 in outside bills as 13 in. A box that measures 11.9 in outside avoids an entire inch on that axis.
- Cut boxes down. Score the corners at the height of the contents, fold the flaps and tape. Dropping a 12 × 12 × 12 to 12 × 12 × 8 takes it from 13 lb to 9 lb.
- Use poly mailers for soft goods. Clothing in a mailer only 2-3 in thick rarely produces a DIM weight above its real weight.
- Compare USPS for medium boxes. Up to 1 cubic foot, USPS bills actual weight, so a 12 × 12 × 12 box of light items costs its true weight there but 13 lb at UPS or FedEx.
- Vacuum-pack compressible items. A comforter compressed to half its volume halves its DIM weight.
Volumetric weight for air and sea freight
Freight uses the same idea at a larger scale, with ratios usually written per cubic meter.
| Mode | Ratio | 1 m³ is charged as | Notes |
|---|---|---|---|
| Express courier | 1:5,000 (cm³/kg) | 200 kg | DHL Express, UPS and FedEx international |
| Air cargo | 1:6,000 (cm³/kg) | 167 kg | IATA convention for general air freight |
| Road freight (Europe) | Often 1:3,000 | 333 kg | Varies by haulier; pallets often priced per pallet space |
| Sea freight, LCL | 1 m³ = 1,000 kg | 1 metric ton | "Weight or measure": billed per revenue ton |
A standard 1200 × 800 mm Euro pallet stacked to 1.5 m is 1.44 m³, which air freight bills as at least 240 kg. Pallet footprints are listed in the pallet size guide, and container capacities in the shipping container guide.
Size limits that come with large boxes
Dimensional weight is only part of the bill for big parcels. Each carrier also has maximum sizes, measured as length plus girth (girth = 2 × width + 2 × height).
| Carrier | Max weight | Max length | Max length + girth |
|---|---|---|---|
| UPS | 150 lb (68 kg) | 108 in (274 cm) | 165 in (419 cm) |
| FedEx Ground | 150 lb (68 kg) | 108 in (274 cm) | 165 in (419 cm) |
| USPS Priority Mail | 70 lb (32 kg) | within girth limit | 108 in (274 cm) |
| USPS Ground Advantage | 70 lb (32 kg) | within girth limit | 130 in (330 cm) |
Example: a 30 × 20 × 20 in box has a girth of 80 in and a length plus girth of 110 in, which is over the Priority Mail limit but fine for Ground Advantage, UPS and FedEx. Additional handling and large-package surcharges start well below these maximums at UPS and FedEx (for example, a longest side over 48 in), so long, light items such as rolled rugs are expensive even when their DIM weight is modest. To convert box dimensions between inches and centimeters, use the unit converter.
Frequently asked questions
Why is my box billed at more than it weighs?
Because its dimensional weight is higher than its scale weight. A 16 × 12 × 12 in box holding a 6 lb comforter has a DIM weight of 2,304 ÷ 139 = 16.6, rounded up to 17 lb, so you pay the 17 lb rate. Carriers price by volume when the parcel is light for its size.
Does dimensional weight apply to small packages?
With UPS and FedEx it applies to every package, however small, although with tiny boxes the DIM weight rarely exceeds the real weight (a 6 × 6 × 6 in box is 216 ÷ 139 = 1.6, billed as 2 lb). USPS applies it only to boxes larger than 1 cubic foot (1,728 cubic inches).
What is the difference between dimensional weight and volumetric weight?
Nothing in practice. US carriers say dimensional or DIM weight; airlines, freight forwarders and European couriers usually say volumetric weight. Both convert volume into a chargeable weight with a divisor.
What was the USPS dimensional weight divisor before 2026?
USPS used 166 until July 12, 2026, when it moved to 139 and began rounding every fractional inch up. The same 16 × 14 × 10 in box went from 2,240 ÷ 166 = 13.5 (14 lb) to 2,240 ÷ 139 = 16.1 (17 lb).
How do I convert a cm/kg divisor to inches and pounds?
Multiply the metric divisor by 0.02768. A 5,000 cm³/kg divisor equals 138.4 in³/lb, and 6,000 equals 166.1. That is why 139 and 5,000, and 166 and 6,000, are treated as the same rule in the two unit systems.
Do padded envelopes and poly mailers get dimensional weight?
They can. Carriers measure soft packages at their fullest point once packed, and a stuffed poly mailer is treated like a box of those dimensions. Flat mailers stay well under the threshold because their height is only an inch or two.