In e-commerce and in store replenishment, a significant part of each order's cost is determined not in purchasing or sales but at the packing table, when the box is selected. If the box is larger than needed, the carrier bills for the space, not for the product. That charge is calculated with dimensional weight, also called volumetric weight or DIM weight.
What dimensional weight is
When carrying light boxes, a van or an aircraft reaches its capacity by volume before weight. To charge for that space, carriers convert a package's dimensions into an equivalent weight and bill whichever is greater: the actual weight on the scale or the dimensional weight from the measurements. DHL, for example, publishes the formula and the rule of billing the greater of the two for its express shipments.
How it is calculated
In metric markets, including Mexico, express services use:
Dimensional weight (kg) = length (cm) × width (cm) × height (cm) ÷ divisor
The most published divisor for express services is 5,000. US domestic services work in inches and pounds with their own divisor, commonly 139 for daily rates. Ground services and negotiated contracts often use different numbers. The divisor that applies to your company is the one in your contract, not the one in an online calculator.
For example, in metric units, a 40 × 30 × 30 cm box (about 15.7 × 11.8 × 11.8 in) weighs 4 kg (8.8 lb) on the scale.
- Volume: 40 × 30 × 30 = 36,000 cm³.
- Dimensional weight with a 5,000 divisor: 36,000 ÷ 5,000 = 7.2 kg.
- Billable weight: 7.2 kg, because it exceeds the actual weight.
If the same product fits in a 35 × 25 × 25 cm box, dimensional weight drops to 4.4 kg. The difference, 2.8 billable kilograms per package, multiplied by thousands of packages a month, is a cost that is not visible in the warehouse but appears on the carrier's invoice.
Causes of higher dimensional weight
An unsuitable number of box sizes
With two box sizes, most orders ship in the large one. With twenty, packers lack a clear criterion and take the closest. A catalog of six to ten sizes, designed around the best-selling products, usually covers most orders.
Box selection by habit
Without a written rule, every packer uses their own judgment. A table at the station, by product or by frequent combination, settles most cases. For multi-line orders the rule can be based on approximate total volume.
Void fill replaces the right box
Paper and air pillows protect the product, but they do not reduce dimensional weight. If a box requires a lot of fill, it is probably not the right size.
The catalog has no dimensions or weights
Suggesting a box or auditing an invoice requires the weight and dimensions of each product. Many companies have item codes and descriptions but not dimensions. Measuring the products that ship most often takes a few days, and its cost is recovered quickly.
How to control it from packing
- Measure current shipments. For two weeks, record the box, actual weight and dimensions of each package. Compare actual and dimensional weight. The share of packages billed by volume indicates how much space you are paying for.
- Define the box catalog from the most frequent products and combinations.
- Write the selection rule and post it at each packing station.
- Record weight and dimensions when each package is closed. It is the basis for auditing the carrier invoice: if the carrier bills 9 kg for a package your record shows at 7.2 kg dimensional, the company has a documented claim.
- Audit the invoice every month against your package records.
Peak season
In Mexico's peak season, from El Buen Fin in mid-November through December, volume increases and box selection becomes less rigorous; it is the period in which the most oversized boxes ship for lack of the right sizes. Confirm your stock of each box size before the season and manage it like any other critical material.
Mexican e-commerce keeps growing: the 2026 Online Sales Study by AMVO, the country's online sales association, puts the 2025 retail e-commerce market at 941 billion pesos, up 19.2%. With more packages, every extra dimensional kilogram has a greater impact on the margin.
How Chainlink records it
In Chainlink WMS, the packer builds each package by scanning the items picked for the order and, when closing the package, enters its weight in kilograms and its dimensions in centimeters. At least one package must have a weight before the order can be sent for review. Each package keeps its code, contents and weight, and the shipment manifest lists every package with its document and weight, so it can be compared with the carrier's invoice.
In every plan, a manually entered weight can be compared with the expected weight (box tare plus the weight of each item), with the option to only warn or to block closing the package when it does not match. In Enterprise, packing stations read the weight directly from the scale and record dimensions with a dimensioner; that equipment is listed as compatible and not yet verified on physical hardware.
Frequently asked questions
Which divisor is used to calculate dimensional weight?
Each carrier sets it for each service. For express services in metric markets the most published value is 5,000 cubic centimeters per kilogram; US domestic services commonly use 139 cubic inches per pound. Your contract may differ, so check it or your carrier's rate guide.
Is dimensional weight always billed?
No. The carrier bills the greater of actual and dimensional weight. A small, heavy package is billed by actual weight; a large, light one by volume.
How can dimensional weight be reduced without changing carriers?
With a box catalog that fits your products, a written rule for choosing the box and a weight and dimension record for every package to identify packages shipped in a larger box than needed.
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