Dimensions Weight is the formula used by UPS, FedEx, and other major carriers to measure shipping costs. Dimensions Weight is usually calculated as weight x length x height / 139 (denominator numbers are negotiable) . The carrier (and Amazon) compares the weight of the package to the dimensional weight calculation and charges the higher of the two costs . If you're not paying attention, you can easily ruin this , and I 'll give my colleague a ridiculously high shipping cost as the £ 1 item was housed in an irregularly shaped box. I made you pay. You need to be paranoid, even after planning your packaging in advance .To ensure that your item 's dimensions and weight are as expected, be Cork Bicycle Repair Zone sure to send the item to yourself for inspection before shipping in bulk to Amazon 's warehouse . Then, when you first ship to Amazon, make sure that the dimensions that Amazon measures match your measurements . Amazon often spoils this, and unless you pay close attention to Amazon's invoices, you may not realize that you're accidentally paying an oversized FBA fee until a few months have passed. I have. Long-term storage penalties are calculated in cubic feet . Amazon's long-term storage charges are typically $ 6.90 per qubit foot or $ 0.15 per unit, whichever is greater. Long-term storage fees are assessed on the 15th of every month. Here are some examples of numbers that show how high these Amazon charges will be. Amazon's long-term storage fee Overall, it's best interests to keep your inventory within 12 months and save money using LTL delivery to Amazon's warehouse.