Carton CBM & Container Loading Estimator
Calculate carton CBM and how many cartons your shipment fits in a standard container.
Reviewed by the ToolNestr Editorial Team — July 2026
How CBM and container loading are calculated
Each carton's CBM is its outer length × width × height, converted to meters: CBM = (L × W × H in cm) ÷ 1,000,000. Total shipment CBM is that figure multiplied by the number of cartons. This total is then compared against a standard container's usable capacity — roughly 28 CBM for a 20-foot container and 58 CBM for a 40-foot container, accounting for the real-world loading efficiency loss from pallets and stacking gaps, not the container's raw theoretical volume.
Freight forwarders quote ocean freight largely by CBM (or by weight for very dense cargo, whichever produces the higher "chargeable" figure), so an accurate CBM calculation directly determines shipping cost — underestimating carton size when planning a shipment risks a shipment that doesn't actually fit the booked container, forcing an expensive last-minute upgrade to a larger one or a second container.
CBM formula (L×W×H/1,000,000 per carton) and standard container usable-capacity figures follow standard freight-industry practice.
Worked example
200 cartons at 60 × 40 × 40 cm each, checking against a 20ft container.
Real-world context
Apparel is notoriously "volume-heavy but weight-light" cargo — bulky but not dense — which usually means it's CBM-limited rather than weight-limited when loading a container, unlike heavier goods that hit the container's weight limit long before filling its volume. This is why apparel shippers focus heavily on carton-size optimization and compression packing to fit more units per CBM.
Consolidating multiple smaller brands' shipments into a single shared container (LCL — Less-than-Container-Load) is a common strategy specifically when an individual shipment's CBM doesn't come close to filling a full container, since paying for an entire container's worth of space to ship a fraction of its capacity wastes money that shared LCL shipping avoids.
Common misconceptions
"A 40ft container holds exactly twice the volume of a 20ft container." Slightly more than double. A 40ft container's usable CBM (~58) is a bit more than double a 20ft's (~28), since fixed loading-inefficiency losses are proportionally smaller in the larger box.
"Container capacity is the container's raw dimensional volume." Real usable capacity is lower. Pallets, load bars, and imperfect stacking always leave some space unused — that's why usable-capacity figures, not raw container volume, are used for planning.
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Frequently asked questions
What is CBM in shipping?
CBM (Cubic Meters) is a carton's volume — length × width × height in meters — used to calculate ocean and air freight charges, since freight is priced by volume (or weight, whichever is greater) rather than just item count.
How many CBM fit in a standard shipping container?
A 20-foot container holds roughly 28-30 CBM of usable space (about 33 CBM total, reduced for real-world stacking/access), and a 40-foot container roughly 58-60 usable CBM — this calculator uses the standard usable-capacity figures for both.
Why don't cartons ever fill 100% of a container's CBM?
Cartons are rectangular boxes packed into a rectangular container, but pallets, load bars, and irregular final-row stacking always leave some unused space — real-world loading efficiency is typically 85-92% of the container's theoretical maximum, which this calculator accounts for.
Should I calculate CBM using outer or inner carton dimensions?
Always use outer carton dimensions (as the box is packed for shipping) since that's the space it actually occupies in the container, not the smaller inner packed-goods dimensions.