What is the CBM calculation formula?

CBM per box = length (m) × width (m) × height (m). If the box is measured in cm, divide by 1,000,000 to convert to m³. The total shipment CBM is the CBM of one box × the quantity. 1 CBM = 1 m³.

How do you choose between LCL and FCL?

As a rule of thumb, LCL—sharing a container with other shippers—tends to be economical for total cargo of 15 CBM or less, while FCL—using a container exclusively—makes more sense above 15 CBM or when schedule and security matter.

What are the loading capacities of 20ft, 40ft, and 40HC containers?

A 20ft DC holds about 28 CBM, a 40ft DC about 58 CBM, and a 40ft HC (high cube) about 68 CBM of usable capacity. In practice, actual loading typically reaches 80–85% depending on box dimensions.

LOGISTICS GUIDE

CBM Calculation and Container Loading Optimization Guide

May 20, 2026 Logistics Guide

Whether you are a shipper handling your first import or export, or a trade manager who books containers every month, one question keeps coming up: "What is the CBM of this shipment, and which container should it go in?" CBM is the starting point for international shipping rates and the baseline for any loading plan. This article brings together everything you need on the job—from the CBM formula to container dimensions, choosing between LCL and FCL, and pallet loading.

1. What CBM Is and Why It Matters

CBM stands for Cubic Meter—the volume of cargo expressed in m³. It is the most fundamental unit for calculating rates in international ocean and air freight, where 1 CBM = 1 m³.

The reason volume (CBM) rather than weight (kg) is the basis is simple: the limits of a container or a vehicle are reached by space before they are reached by weight. For cargo that is light but bulky—apparel, household goods, packaging materials, and the like—charging by weight would leave the carrier out of pocket. That is why CBM, a volume-based unit, sits at the center of freight pricing.

2. The CBM Formula and a Step-by-Step Example

The formula for the CBM of a single box is straightforward.

CBM = length (m) × width (m) × height (m)

The most common mistake on the job involves units. Box dimensions are usually measured in cm, but CBM is based on meters. If you measured in cm, you have to divide by 1,000,000 to convert to m³.

Let's work through a box measuring 60cm (L) × 40cm (W) × 40cm (H) step by step.

Convert to meters: 0.6m × 0.4m × 0.4m
CBM per box: 0.6 × 0.4 × 0.4 = 0.096 CBM
Total CBM: CBM per box × quantity. For 100 boxes, 0.096 × 100 = 9.6 CBM

If your shipment includes several types of boxes, calculate the CBM for each type and add them together to get the total CBM.

3. Container Dimensions and Usable Capacity

Once you know your total CBM, you need to decide which container to use. Here are the internal dimensions and usable capacity of the three container types most commonly used in international ocean freight.

20ft DC — interior approx. 5.89 × 2.35 × 2.39m, usable approx. 28 CBM
40ft DC — interior approx. 12.03 × 2.35 × 2.39m, usable approx. 58 CBM
40ft HC (high cube) — interior approx. 12.03 × 2.35 × 2.69m, usable approx. 68 CBM

A 40HC has the same length and width as a 40ft DC but stands about 30cm taller. Because it fits more volume within the same shipping unit, it is a frequent choice for cargo that is light but bulky.

4. LCL vs. FCL — How to Choose a Shipping Method

When shipping cargo by the container, you have two options.

LCL (Less than Container Load) is consolidated shipping, where multiple shippers share a single container. Because rates are charged on a CBM and weight basis, it suits smaller shipments. The trade-off is a somewhat longer lead time, since consolidation and customs steps are added.

FCL (Full Container Load) uses an entire container exclusively. With a flat rate per container, the unit cost drops as your load factor rises, and door-to-door scheduling is easier to manage.

The usual dividing line is 15 CBM. When total cargo is 15 CBM or less, LCL is often the more economical choice; above that, or when schedule and security are priorities, FCL frequently wins out. That said, the answer can vary with the nature of the cargo and the infrastructure at the destination, so it's best to review it together at the quotation stage.

5. Loading Efficiency — Why You Can't Fill a Container 100%

This is a point that often trips people up on the job. A 40HC has 68 CBM of usable capacity, yet when you actually load the boxes, loading frequently comes to a stop somewhere around 60 CBM.

The reason is that boxes have a fixed, rectangular shape. Liquids and grains fill every gap, but unless boxes divide evenly into the container's internal dimensions, empty space is left along the edges. For example, stack boxes that are 30cm on a side inside a 40HC with a 269cm internal height and only 8 tiers (240cm) fit, leaving 29cm of empty space.

That is why the key to higher loading efficiency is to design box dimensions to match the container's internal dimensions as closely as possible. Adjusting a box side by just a few centimeters can dramatically change how many units fit in a container—and that translates directly into lower freight costs.

6. Loading by the Pallet — T11, T12, and EUR

If you ship out and transport by the pallet, you also need to factor in pallet dimensions. The pallets most commonly used in Korea are as follows.

T11 (1100 × 1100mm) — the Korean KS standard. Optimized for domestic logistics and warehousing infrastructure
T12 (1200 × 1000mm) — ISO-compatible. Advantageous for loading export containers
EUR (1200 × 800mm) — the European standard. Used for exports bound for Europe

If domestic transport and storage is the main purpose, T11 is generally more efficient; if you have export container loading in mind, T12 usually is. As with containers, when you stack boxes on a pallet, how well the box dimensions and the pallet size match determines the loaded quantity.

7. Check Ahead with a Free CBM Calculator

The CBM formula itself is simple, but working out box rotation, leftover space, and stack tiers by hand takes time and invites errors. RUNIC offers two free calculators you can use for a pre-check before requesting a quote.

Box-Fit Calculator — enter the box size and product size, and it compares all six rotations to work out automatically how many items fit in one box. Supports a mixed-packing verification mode.
CBM Calculator — enter box dimensions and quantity, and it automatically calculates total CBM, the right container (20ft, 40ft, 40HC), and the maximum loadable quantity, showing the loading layout in 3D.
Pallet CBM Calculator — choose a T11, T12, or EUR pallet, enter box dimensions and stack height, and it computes boxes per layer, the number of tiers, and total CBM.

Both tools are ready to use with no sign-up and work on mobile. Confirming your cargo's CBM and loading structure in advance—before you request an import/export quote—makes rate negotiations far smoother.

RUNIC's International Freight Forwarding

Built on K-One Gimpo Logis, RUNIC is an integrated logistics partner that runs 3PL fulfillment, freight-truck brokerage, international express for businesses, and international freight forwarding from a single team. Our international freight forwarding covers all modes—ocean, air, and land—together with FCL and LCL and the full import/export customs process, and we arrange port and airport inland transport directly through our own brokerage network. Whenever you need an accurate rate quote after calculating your CBM, get in touch.

Need an LCL or FCL forwarding quote? Run a pre-check with the CBM calculator, then leave us your quote request

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