When the Weights Do Not Add Up: Gross, Net and Volume Checks

Weight is the quickest cross-check you can run on a load, because it needs no unpacking: a scale, a tape measure and a little arithmetic. It cannot tell you that every item inside a carton is right, but in a few minutes it can tell you that something is wrong with a pallet that otherwise looks fine. To use it well you need to know what the figures on the papers mean, and where small differences come from.

What the figures mean

• Gross weight is the goods plus all of their packing: inner packaging, the carton and, for a pallet, the pallet itself and the wrap.
• Net weight is the goods alone, with no packaging.
• The difference between the two is the weight of the packing, often called the tare.
• Volume, in cubic metres, is length times width times height of a carton or pallet in metres, multiplied by the number of units.

The packing list usually gives gross and net weight per carton or per line, together with totals. The bill of lading usually gives a total gross weight and a volume. Before you compare anything, check which kind of weight each paper is quoting.

Where small differences come from

• The weight of pallets and wrap is counted in one paper and left out of another.
• Rounding: figures rounded to whole kilograms on each line can add up to a different total.
• The scale itself: its smallest division, its accuracy, and whether it has been zeroed. A floor scale on site gives an indication, not a certified measurement.
• Different pallet types, such as timber against plastic.
• Moisture in the cartons or in the goods.
• A stack that overhangs its pallet takes up more volume than the cartons alone suggest.

Quick checks at the dock

1. Weigh one sample carton, write the figure down and compare it with the gross weight per carton on the packing list.
2. Weigh one full pallet and compare it with cartons × carton gross weight, plus the weight of the pallet and wrap.
3. Measure one carton, work out its volume and multiply by the number of cartons. Compare the result with the volume on the papers.
4. If a weighbridge is available, compare the weighed total with the bill of lading. The empty weight of a container is printed on its doors.
5. Record every reading with the time and the scale used.

When a gap needs a second look

A gap in the same direction on every pallet, beyond the scale's smallest division, points to a systematic cause, most often a pallet weight that one paper includes and the other does not. A single pallet far from the others calls for opening it. A pallet lighter than listed may hold missing or half-filled cartons. A pallet heavier than listed may carry moisture, extra items, a different product or a different pallet type. Where the measured volume is larger than the papers show, the cartons may be bigger than listed, and that matters for storage space and for freight.

A conditional example. The packing list shows 40 cartons per pallet at 18.5 kg gross each, which is 740 kg, and the pallet with its wrap adds 20 kg, so you expect 760 kg. The scale reads 733 kg, which is 27 kg light, or about 3.6 percent. Another pallet of the same type reads 758 kg, so this pallet is the odd one out. The count shows 40 cartons, so the number is right, but you weigh the cartons one by one: six of them weigh 14.0 kg instead of 18.5. Six times 4.5 kg is 27 kg, exactly the gap. You open the six and count their contents against the packing list. The count of cartons would never have raised the question.

What to write in the report

State the scale used and its smallest division, the readings and their times, the expected figure and how you worked it out, and the difference in kilograms and in percent. Do not write that the shipment is "underweight"; write what was weighed and what the paper says. A reading shows that something deserves a look; opening the cartons produces the evidence you can send to a supplier.

In short

Weight and volume are cheap checks that catch what a carton count cannot. Wherever a scale is available on site, CargoChek compares weights and volumes with the packing list and the bill of lading and notes any gap together with the readings taken.