Dimensional weight: why you are charged more than your package weighs
You ship a package that weighs two kilos and get billed as if it weighed six. That is not a carrier error: it is dimensional weight, and understanding it is one of the fastest ways to cut your shipping cost without negotiating rates.
Why it exists
A truck fills up by volume long before it fills up by weight. A large box full of pillows takes the space of several heavy boxes while weighing almost nothing. If carriers billed by kilos alone, those shipments would travel nearly free while consuming all the space. So carriers calculate two weights and charge the greater of the two.
How it is calculated
The standard formula multiplies the three dimensions in centimeters and divides by a factor. In Mexico the most common factor for domestic parcel is 5,000, though it varies by carrier and service level, so confirm it with yours:
| Step | Operation | Example |
|---|---|---|
| 1. Measure the box | Length × width × height in centimeters, already packed. | 40 × 30 × 25 cm |
| 2. Multiply | Gives you the volume in cubic centimeters. | 30,000 cm³ |
| 3. Divide by the factor | Volume ÷ 5,000. | 30,000 ÷ 5,000 = 6 kg |
| 4. Compare | Actual weight against dimensional weight; the greater is billed. | Weighs 2 kg, billed as 6. |
Check the factor with your carrier: not all use 5,000 and some apply a different one to express services.
What you can actually do about it
- Fit the box to the product. This moves the needle most. Every extra centimeter of box is paid on every shipment, all year.
- Stock several box sizes. Shipping everything in one size for convenience means paying for air on small orders.
- Look at your filler. Needing a lot of filler usually signals the box is larger than it needs to be.
- Consolidate orders from the same customer. Two small boxes usually cost more than one well packed.
- Watch for bulging. A deformed box measures larger than it should, and carriers measure what they see.
Where it hurts most
If you sell bulky, light product — lighting, furniture, toys, home goods, bedding — dimensional weight is probably your largest logistics cost, above storage. It is worth running the numbers on your five best sellers to see how much you are paying in air.
It is the same logic as storage, incidentally: there you also pay for space rather than weight. If you are sizing your operation, see how much warehouse space you need.
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