How to calculate W/M

Written by ian kelly
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How to calculate W/M
Use the W/M method to calculate your freight charges. (Stockbyte/Stockbyte/Getty Images)

If you’re in the import/export business, most of your cargo is transported by sea aboard container ships. When you don’t have sufficient cargo to fill a container, the shipment is known as "less than containerload," or “LCL,” cargo. If the item is too large to fit inside a container it is called “Breakbulk” cargo. In both cases you must use the W/M method to calculate the freight charges. “W/M” is the acronym for “Weight or Volume,” whichever is greater. The charges are based on multiples of 1,000 kilograms versus volume in cubic metres.

Skill level:

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Things you need

  • Tape measure
  • Scale
  • Calculator

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  1. 1

    Measure the length, width, and height of the crates or pallets used in a particular shipment. Calculate their volume using the following formula: length x width x height = volume. Add the results together to arrive at the physical space your shipment will take up. This is usually measured in cubic metres.

  2. 2

    Weigh each crate, box or pallet and combine the total. Compare the volume arrived at in Step 1 to the weight in kilograms. Use the higher of the two to calculate the W/M freight charges.

  3. 3

    Multiply the amount arrived at in Step 2 by the W/M rate to arrive at the total freight charges for the shipment. For example, suppose the W/M rate is £75.00 and you have 12 pallets each weighing 175 kilograms and measuring 130 cm x 128.5 cm x 110 cm. Then 12 x 175 = 2,100 kilograms, and 12 pallets x 123 cm x 128.5 cm x 108 cm, divided by 1,000,000 cubic centimetres = 22 cubic meters. Therefore the volume is greater than the physical weight, so the freight charges would be £75.00 x 22 cubic meters, which equals £1,650.00.

Tips and warnings

  • Your shipper my include surcharges based on a) fluctuating international currency rates, know as a currency adjustment factor, and b) bunker adjustment factor based on the cost of bunker fuel during periods of unstable oil prices.

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