Calculating Dimensional Weight – The Dark Matter of Shipping

Have you ever scheduled freight for shipment, only to have your forwarder come back and tell you that the “chargeable weight” or “dimensional weight” was three or four times more than the shipment weighed in your warehouse?

What the heck is going on here? Is your forwarder some kind of crook? Hopefully not. Odds are, your freight was subject to dimensional weight charges.

Dimensional what?

Dimensional weight has long been the dark matter of the shipping industry:?? Most people aren’t really sure what it is, but it seems to affect everything. In today’s post, we take a detailed look at what dimensional weight is, how it is calculated and what you can do to minimize the effect of this mysterious force on your freight bill.

DIMENSIONAL WEIGHT EXPLAINED
Dimensional weight, also known as “volumetric weight”, is a unit of measure that has been adopted worldwide by the transportation industry to account for the space occupied by cargo in the hold of an aircraft, truck or ocean vessel. Essentially, it protects the carrier from catastrophic losses that would occur on low weight, high volume cargo if freight were only charged by gross weight. While it has been used historically for air freight shipments, and to a lesser extent trucking, a form of volumetric weight can also be applied to ocean shipments as well. More on this in a moment.

Dimensional Weight CalculationThe classic example: Ping pong balls. Were it not for dimensional weight calculations, a shipper could completely fill a truck to the brim with ping pong balls and claim they should only be charged for 50 pounds of cargo, because that’s all they weigh. Ping pong balls are a classic high volume, low weight item. They are essentially all air.

In this case, the shipper would pay for the greater of the actual weight or the chargeable, dimensional weight. So what is the hypothetical, dimensional weight on a 24′ truck full of ping pong balls, if filled to the ceiling, front to back?

Answer: Approximately 13,682 pounds!

Hmmmm… Maybe this is something we should look into further.

HOW TO CALCULATE DIMENSIONAL WEIGHT
Dimensional Weight CalculationSo how do you calculate this dimensional weight thing? The answer, like so many things in life is, it depends.

Air Freight Calculations
First, let’s look at air freight. That is where the concept of dimensional weight, or “dim weight”, originated. There are two primary means of calculating dimensional weight: international and domestic. The international calculation differs, primarily to account for the difference in operating costs for domestic versus long-distance international flights. The two calculations used are as follows:

  • Domestic Air Freight (inches): (Length x Width x Height) / 194
  • International Air Freight (inches): (Length x Width x Height) / 166

The 194 or 166 denominator is what is commonly referred to as the “dim factor”.

As an example, international shipping on a standard 48 x 40 x 60 inch pallet weighing 300 pounds, would be charged at a dimensional rate of 694 pounds: (48 x 40 x 60)/166.

There are also separate formulas for centimeters/kilograms for those of you who speak metric, but let’s not confuse things here.

Interestingly, shipments to Hawaii, Alaska and Guam are normally charged at the “domestic rate”. I’ve never understood the rationale for that one.

Ground Freight Calculations
NMFC-Codes-freight-classJust as the air freight folks have their formulas, the trucking industry has its own form of black magic. Common carriers have their own, infamous set of NMFC “freight classes” based on the density of an item. It is a closely guarded tome of thousands of classifications for everything from toothpicks to lead batteries. The manual or software used to look up these freight classes is available for purchase, but at a rate that makes it prohibitive for most shippers.

The actual formula used to calculate “freight classes” is based on the density of an item per cubic foot. However, a discussion of it here is beyond the scope of this post. That’s a post for another day.

To add insult to injury, there are truckers who do not operate as a “common carrier” and who play by different rules. These include independent truckers and airline ground feeders. In these instances, they often apply a more favorable “dim factor” of 250, presumably reflecting the lower operating cost of a truck versus an aircraft. In other words:

  • Ground Freight: (Length x Width x Height) / 250

That is, of course, unless the carrier opts for the more favorable 194 “dim factor”.?? It varies by carrier.

Confused yet?

Ocean Freight Calculations
Lets look briefly at shipments of partial container freight, otherwise known as Less-Than-Container-Load (LCL) shipments. Not to be left out, the ocean folks have devised their own special way of calculating dimensional weight for LCL moves. (For full containers, you own the whole container, so volume is irrelevant.)

Note that ocean carriers more often refer to dimensional weight as volumetric weight, typically measured in cubic meters, or CBM’s. Charges are typically based on the greater of the weight in metric tons (1,000 kilograms) or measurement in CBM’s, based on one ton per CBM and are noted as “W/M” on most documents.

Fortunately, calculation of cubic meters is very simple:

  • Ocean Freight (centimeters): (Length x Width x Height) / 1,000,000

For example, a pallet measuring 120 x 100 x 150 cm and weighing 1000 kgs = 1.80 CBM. Since 1.80 CBM is greater than 1.00 metric tons, the chargeable, volumetric weight is 1.80 CBM.

Clear as mud, right?

HOW TO MINIMIZE DIMENSIONAL WEIGHT CHARGES
Great, you now know the secret of dark matter, but how to minimize its impact on your shipping budget and career future? It turns out that it’s not that difficult. A little bit of common sense and advance planning can save you a bundle and make you a shipping hero.

Minimize Carton Size
Cartons
It’s really quite simple: use the smallest cartons possible. Once you know the magic formulas listed above, you can see the effect. Using international air freight as an example:

  • Carton A: 24 x 24 x 24 inches = 83 lbs of chargeable weight.
  • Carton B: 20 x 20 x 20 inches = 48 lbs of chargeable weight.

Decreasing the carton size by just 4 inches, lowered the chargeable weight by an astounding forty-two 42%!

Minimize Pallet Size
PalletsWe see shippers make this mistake all the time. They will take three cartons of 20 x 20 x 20 inches each. Each has a “dim weight” of 48 pounds apiece, per the example above, for a total of 144 pounds.

Unfortunately, the well-meaning guys in your shipping department just strapped them to a 48″ x 40″ pallet for safekeeping. Guess what? Your chargeable, dimensional weight just went through the roof. Why?

Chargeable weight = (48″ x 40″ x 24″*) / 166 = 278 pounds of chargeable air freight weight! That’s an increase of nearly 100%!

*Note: 24 inch height = a layer of 20 inch cartons plus the 4-inch tall pallet.

It is critical that you use the smallest pallet possible, not just the standard 48 x 40 inch skid laying around in the corner of the warehouse!

CONCLUSIONS
Dimensional weight is quickly demystified, once you understand the simple math behind the concept. It’s all about minimizing your shipment size and packing the freight as efficiently as possible. Don’t just grab the first carton that is convenient. With just a little bit of common sense and advanced planning, you can decrease your freight bill dramatically, impress your boss and be on the way to that next big promotion for saving your company a bundle.

 

Comments

  1. When shipping domestically, what standards are set in determining whether cost is incurred by dimensional weight or actual weight and who sets the standard? Example: An 18x12x12 box weighing 15 lbs travels at actual weight and not dimensional (which is greater), while a 22x15x15 box weighing 15 lbs travels at dimensional weight which is greater. I know 84″, 108″ and 165″ are the deciding cost factors, but why?

    • Sandy,

      When shipping domestically, the choice of whether or not to apply dimensional weight to a shipment is largely at the discretion of the carrier. Some choose to use NMFC freight classes , while others use dim weight, as described here. In addition, some may choose to use a dim factor of 194, while others use a more favorable factor of 250. The only important thing is that they apply it consistently and fairly.

      As for your comment that 84″, 108″ and 165″ are the deciding cost factors, I am not familiar with that, unless you are referring to the lengths at which some carriers apply an oversized charge.

      Bottom line: Always make sure you check out the carrier’s dim weight policy before shipping with them.

  2. I want to know surface weight calculation formula

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