If you ship internationally, you’ve met the 5,000 cm³/kg divisor. FedEx and UPS both use it for metric dimensional weight (FedEx; UPS). A common claim is that it’s more forgiving than the US 139 divisor. It isn’t — the two are almost the same number in different units.
The two formulas
Inches → pounds: DIM weight (lb) = (L × W × H in inches) ÷ 139 Centimetres → kilos: DIM weight (kg) = (L × W × H in cm) ÷ 5,000
Convert 5,000 cm³/kg to imperial (1 in³ = 16.387 cm³, 1 lb = 0.4536 kg) and you get about 138 in³/lb. That’s within 0.4% of 139. FedEx in fact applies 139 to international shipments measured in inches.
Where the small differences come from
The divisors match; the rounding doesn’t. FedEx and UPS round each measurement up to a whole unit and the result up to a whole pound or kilogram, so the same box can bill slightly differently in inches and centimetres. Take a 30 × 25 × 20 cm box:
| Measured in | Rounded dimensions | DIM weight |
|---|---|---|
| Centimetres (÷ 5,000) | 30 × 25 × 20 cm = 15,000 cm³ | 3 kg (6.6 lb) |
| Inches (÷ 139) | 12 × 10 × 8 in = 960 in³ | 7 lb (3.2 kg) |
The inch version is higher only because 11.8 × 9.8 × 7.9 inches rounds up to 12 × 10 × 8. Which unit applies depends on the service and origin you ship from.
5,000 vs 6,000
Some services use 6,000 cm³/kg instead. DHL Global Forwarding applies a 1:6 ratio — divide by 6,000 — for air freight (DHL Global Forwarding); that’s about 167 kg per cubic metre, versus 200 kg at 5,000. A 6,000 divisor gives a lower dimensional weight for the same box. Express parcel carriers — FedEx, UPS, DHL Express and, for international parcels, Parcelforce (Parcelforce) — use 5,000.
A box of t-shirts, 40 × 30 × 25 cm, weighing 3 kg, sent by FedEx or UPS internationally:
- Volume: 40 × 30 × 25 = 30,000 cm³
- DIM weight: 30,000 ÷ 5,000 = 6 kg
- Actual weight: 3 kg
- Chargeable weight: 6 kg
At 6,000 cm³/kg the same box would be 5 kg.
How to reduce international DIM charges
- Compress soft goods. Vacuum or compression bags can shrink clothing and bedding a lot; measure the packed result.
- Avoid double boxing where it isn’t needed. A retail box inside a shipping box adds volume you pay for.
- Measure in whole units. Since fractions round up, choose box sizes that are whole centimetres or inches.
- Compare consolidation. One larger package sometimes costs less than two smaller ones; run both through your rates.
Customs and DIM weight
Dimensional weight affects the carrier’s shipping charge, not customs duty, which is based on the declared value of the contents.