Container Loading Calculator — Check Cartons / Pallets per 20GP, 40GP, 40HQ

How many cartons or pallets fit in a 20GP / 40GP / 40HQ / 45HQ container? Enter your packing details to get the loading quantity, total weight and volume utilisation.

Typical container dimensions

Data sources: Internal container dimensions shown here follow the widely used ISO 668 standard nominal dimensions (20GP ≈ 5,898 × 2,352 × 2,393 mm; 40GP ≈ 12,032 × 2,352 × 2,393 mm; 40HQ ≈ 12,032 × 2,352 × 2,698 mm; 45HQ ≈ 13,556 × 2,352 × 2,698 mm). Capacities (33.2 / 67.7 / 76.4 / 86.1 CBM) are the product of the internal dimensions. Typical maximum payload figures (20GP ≈ 21,700 kg, 40GP ≈ 26,500 kg, 40HQ ≈ 26,500 kg, 45HQ ≈ 27,600 kg) are industry planning estimates — the real limit is set by each carrier and by road regulations, so confirm it with your forwarder before finalising.

How a container loading calculator works

A container loading calculator answers the practical export question: how many of my cartons or pallets actually fit in the container I am about to pay for? The calculation starts with the internal (useful) dimensions of the box rather than its nominal outside length. A 20-foot standard container, for example, is about 20 ft long on the outside but only 5,898 mm of usable length inside, once the corner posts, door frame and wall thickness are discounted. The same applies to the width (2,352 mm) and height (2,393 mm for standard, 2,698 mm for high-cube units). Only these internal dimensions matter for packing.

The loading calculation, step by step

For loose cartons the tool first checks the three possible orientations of the carton against the three internal dimensions of the container. Because a box can be turned on any of its edges, there are up to six orientation combinations; the calculator evaluates them all and keeps the one that yields the largest whole number of boxes per layer and per stack. It then multiplies the layers to get a theoretical maximum, applies the container’s payload limit as a weight cap, and finally applies a loading efficiency factor to model real-world losses. For pallets it takes a different route: it works out how many pallet footprints fit on the floor in each of the two rotation possibilities, multiplies by how many layers of pallets fit in the internal height, and caps that figure by the payload.

Volume or weight — which one limits you first?

Every container has two independent limits: how much space it can hold (measured in cubic metres, CBM) and how much it can safely carry (the maximum payload, usually in kilograms). The one you hit first depends on the density of your cargo. Springs and spring parts made from steel wire are dense — a carton of compression springs quickly approaches the weight limit even when it only fills part of the container’s volume. Light products such as foam, garments or plastic parts, by contrast, fill the cubic capacity long before they reach the payload. Our calculator reports both and tells you which constraint is binding, so you do not pay for a second container because you under-specified the first.

Why the real number is 85–90% of the theoretical maximum

Pure geometry assumes every carton is identical and stacks perfectly with zero gaps. In a real warehouse that ideal never happens: cartons bulge, dunnage is needed to stop shifting, the door frame eats a little height, and stacking patterns leave odd gaps at the edges. Accumulated industry experience is that a well-loaded container typically reaches 85–90% of the theoretical maximum, and our calculator applies a 90% efficiency by default. If your cartons are irregular, you should lower the efficiency; if they are a uniform, rigid size, 90% is a sensible planning figure. Always confirm the final count with your freight forwarder before booking.

How we pack spring products

At CHENJI we pack compression springs, extension springs, torsion springs, disc springs, railway suspension springs and wire forms in cartons sized to protect the finish and to stack cleanly inside a 20GP or 40HQ. Small springs go into inner plastic bags and then into corrugated cartons; larger or heavier parts are packed in cartons on pallets, with the pallet height kept under 2,600 mm so two layers still fit in a 40HQ’s internal height. Because the goods are heavy relative to their volume, our loading plans are usually weight-limited, and we use this same calculation when we prepare the packing list and confirm the container size for an order.

Common container loading mistakes

The most frequent errors are: using the outside dimensions of the container instead of the internal ones; forgetting that payload limits vary between carriers and with road regulations, so a weight that is fine on paper can be refused at the terminal; assuming all cartons rotate freely when printed directional arrows limit the orientation; and ignoring the 85–90% efficiency loss, then discovering the container is not quite full after it is already sealed. Checking volume and weight together, which is exactly what this tool does, avoids those surprises before you commit to a freight booking.

How to use this calculator

Enter the container type, then either your carton dimensions and unit weight, or your pallet footprint and height. Leave “loading efficiency” at 90% for a realistic planning figure, or adjust it. The calculator returns the estimated quantity, the CBM actually used, the volume utilisation percentage and the total cargo weight, and flags whether volume or payload is the limiting constraint. You can switch between metric and imperial units and toggle carton rotation. Use the numbers to decide between a 20GP and a 40HQ and to prepare your packing list.

Frequently asked questions