From finding the best packaging materials for shipping and fulfillment centers to calculating the freight rate of your cargo, there’s quite a lot that goes into shipping. Figuring out your shipping costs, however, is often pretty straightforward. By knowing the weight of your shipments, you should be able to figure out how much they will cost, right? 

While that’s often the case, what if you’re shipping a very large box of feathers? This is an unlikely example, but the point will apply to any lightweight shipment. Since feathers weigh so little, the cost to ship should be next to nothing despite the large size of your box or shipping container. Except, size matters. Shipping companies factor in the size of your shipment by using something called CBM.

So what is CBM? It stands for cubic meter and is used to measure volume. 

That’s the easy part. But when we ask what is CBM shipping, the calculations get a bit more complicated. This guide will go over CBM and how you can use it to figure out your likely shipping costs.

What is CBM?

As stated, CBM stands for cubic meter and it is a measure of volume.1 Once you know the CBM of your shipment, you can use it to determine the chargeable weight, which we’ll go into further in just a bit. First, let’s look at how to calculate the CBM of any package:2

  • Square or rectangular – To calculate CBM, we need to use the same equations we learned in high school geometry to figure out volume. The easiest of these is for squares or rectangles. Simply multiply the dimensions length x width x height. For instance, a package 1 meter long, 1 meter wide, and 1 meter high would be 1 CBM.

    For a slightly more complicated example, let’s look at a package 3 meters long by 2 meters wide and 4.5 meters high. The equation would look like this: 3 x 2 x 4.5 = 27 CBM
  • Cylinder – Unfortunately, not all packages are perfect rectangles. Another shape you may run into is a cylindrical package. To calculate CBM for this, you’ll need to start by figuring out the radius. The radius is the measurement from the center of a circle to its circumference (or half the diameter). Once you have the radius, use this equation:

    𝜋 x height x radius² = CBM

    In this equation, 𝜋 is estimated at 3.14. To square the radius, multiply it by itself.
  • Irregular shape – For oddly shaped packages, you will measure the longest points of length, width, and height and use the same equation you would use for a rectangle.


CBM is calculated using meters. Since we often measure in inches, it’s worth knowing how to convert inches to meters. An inch is about 0.25 meters, so to convert, you can multiply by 0.25 (dividing by 4 will yield the same result). 

However, for some packages (like those shipped with USPS or FedEx), there are equations that utilize a CBM in inches. Either way, it’s best practice to conduct a CBM calculation in meters. 

How Does CBM Affect Shipping Costs?

Now that you know how to calculate CBM, the obvious question is: so what? Let’s go back to our example about the box of feathers. In that case, the shipping company would determine the box’s volumetric weight and compare it to the box’s gross weight. Whichever is higher will be the chargeable weight. Let’s look at those terms separately:

  • Gross weight – The actual weight of the package. Often expressed in kgs, tons, or lbs. 1,000kgs = 1 ton.
  • Volumetric weight – Also called the dimensional weight or DIM weight. An estimate using CBM to account for the size of lightweight packages.
  • Chargeable weight – The weight used to determine how much you will be charged. It can be either gross weight or DIM weight, whichever is higher.

Again, while the weight of a package determines its shipping cost,  calculating CBM rate matters in instances where the parcel is extremely light. In this example, it’s done by calculating the total volume of a box and using the measurement to determine the freight cost of shipping.

Calculating DIM Weight

So, where does CBM come in? CBM is used to calculate the DIM weight of your package. To get your DIM weight you multiply your package’s CBM by a DIM factor. 

This DIM factor will change depending on how you’re shipping your package. For instance, because ocean freight tends to be concerned with space, their standard DIM factor is 1 CBM is equivalent to 1000 kg. So, if your package is 2CBM but it weighs less than 2 tons (2,000kg), your chargeable weight is still 2 tons.3

Of course, those are for large shipments. For a shipment with USPS, you may be charged for your DIM weight if your package’s volume exceeds one cubic foot (1,728 cubic inches). To determine if your package hits this mark, use the same equation from above to determine CBM (but calculate in inches). If your result is over 1,728 cubic inches, divide by 166. The result is your DIM weight.4

If you’re shipping using USPS or FedEx, an even easier way to determine your DIM weight is by using Shipware’s easy-to-use DIM calculator. By comparing your results to the actual weight of your package, you should be able to easily see what your chargeable weight will be.

A Little Math Goes a Long Way In Helping You Ship Smarter

CBM, DIM, geometry, and equations—shipping can be complicated. But by learning a little about the ins and outs of shipping calculations, you can stay ahead of the curve and maximize every mile your package goes. 

There’s a lot more that goes into shipping, from learning how to ship internationally and how to track parcels to determining how to handle returns as a small business. And it can all feel overwhelming. But Shipware can help with your shipping needs and logistics and make your life easier. 

At Shipware, we provide solutions for reducing freight rate, improving customer satisfaction, and increasing your profits. Contact us today to learn more and get started!



  1. UPS. Cubic Meter (CBM).
  2. Marine Insight. What Is CBM Rate In Shipping?
  3. Drip Capital. CBM | Meaning, Calculation, & More.
  4. USPS. What are the Different Ways Parcels are Priced?