Weight Distribution Rules for Container Loading
Get the weight balance wrong and your cargo shifts, the container floor buckles, or the truck fails a roadside axle check. Use the checker below before you load.
Zone weights
Divide your cargo into three equal zones along the container length
top-down view
Distribution analysis
Enter zone weights above to analyse your load
This checker provides guidance only. Always verify with your carrier's container data plate, a qualified packer, and applicable transport regulations in your country.
The Four Rules That Govern Every Container Load
Violate any one of these and you risk cargo damage, port holds, or road fines. Master them and every container you pack will be compliant.
Stay Within Maximum Payload
Every ISO container has a Maximum Gross Weight (MGW) stencilled on the door data plate. Subtract the tare weight from the MGW to get maximum payload. Overloading is illegal in virtually every jurisdiction - it triggers customs holds, invalidates your cargo insurance, and exposes the shipper to personal liability. Always check the actual tare weight on the container, not a published average.
Respect the Floor Load Limit
Standard ISO containers are rated at approximately 1,500 kg/m² of floor contact area. A 3-tonne machine on four 10 cm × 10 cm feet exerts 75,000 kg/m² - fifty times the limit - even if the total weight is within payload. The fix is simple: add spreader boards or timber dunnage under the cargo to spread the load across a larger area. Always calculate floor pressure before loading any machinery or dense cargo.
Control the Centre of Gravity
The longitudinal centre of gravity (CG) must fall within the middle third of the container length - ideally 40–60% from the front wall. A rear-heavy load creates a lever arm that stresses the container frame, overloads the truck's rear axle, and can cause trailer instability at highway speed. Vertically, keep the CG as low as possible: heaviest cargo on the floor, lightest on top, never the reverse.
Maintain Lateral Balance
The left-to-right weight difference must not exceed 10% of total cargo weight. An unbalanced lateral load twists the container frame over time, causes uneven tyre wear on the truck, and creates handling issues at high speed. Pack mirror-image loads where possible. If the cargo is asymmetric, use timber blocking or ballast weight on the light side to compensate.
Four Loading Patterns That Work
How you sequence and position cargo matters as much as the total weight. These four patterns are used by professional container packers worldwide.
Heavy-First Principle
Load the heaviest items first, directly onto the container floor, against the front wall. This keeps the CG low and longitudinally forward, minimises the risk of crushing lighter goods, and gives you a stable base to build on. Never stack heavy items on top of lighter ones - the weight will either crush the lower cargo or shift the CG dangerously high.
Interlocking (Brick-Bond) Stacking
Stack cartons in a brick-bond pattern, alternating the direction of each layer. This distributes point loads across a wider base and prevents column-stacking - where a straight vertical stack concentrates all upper load onto the four corners of the bottom carton. A 10-layer column of cartons can crush the bottom tier even when individual carton compression ratings look acceptable.
Block and Brace Every Void
Fill all gaps larger than 5 cm with dunnage bags, air pillows, foam blocks, or timber blocking. Unsecured cargo experiences ±0.3g longitudinal and ±0.5g transverse G-forces during sea transport. Over a 25-day voyage, even small gaps allow cargo to build momentum through repeated wave motion - and a full pallet of goods shifting by even 20 cm can collapse the entire load.
Door-End Loading
Load the lightest cargo nearest the doors. The rear zone should carry no more than 30–40% of total weight. This prevents cargo from pushing against the doors during hard braking, keeps the vehicle's rear axle within legal weight limits, and makes it safer to open the container at destination. Never load so tightly that cargo is under pressure against the door seals.
Mistakes That Cause Cargo Claims
These are the errors cargo surveyors find most often after damage incidents. All of them are preventable.
Column Stacking
Stacking boxes in straight vertical columns concentrates the entire upper load onto the bottom carton's corners, far exceeding the manufacturer's compression rating. Always use a brick-bond interlocking pattern.
Door-Heavy Loading
Loading the heaviest items at the door end shifts the CG rearward, overloads the rear axle, and risks cargo falling out when the doors are opened at destination. Heaviest items go to the front.
Unfilled Voids
Any gap larger than 5 cm is an invitation for cargo to shift. During a multi-week ocean voyage, repeated wave motion causes small individual movements that accumulate into full cargo collapse.
High Point Load on Small Footprint
A 2-tonne machine on four small feet can exert 40,000+ kg/m² - well above the 1,500 kg/m² floor limit. Always calculate floor pressure for any machinery and use spreader boards.
Skipping Cargo Lashing
Shrink wrap and banding are packaging - not securing. The CTU Code requires positive restraint: lashing straps anchored to container D-rings, friction mats under pallets, or timber blocking for heavy items. Each D-ring is rated at 1,000 kg WLL.
Loading Into a Damaged Container
A split floor board, rust-through on the roof, or a bent door seal can all cause water ingress and structural failure. Always inspect the container before loading: tap the floor for hollow sounds, check corners for rust, verify the roof and seals are intact.