You probably know that the size and weight of your Amazon FBA items can impact how much you pay in fees, but the way those things are determined can be confusing — which is how so many people end up being overcharged in fees. Knowing what size range your packages fall into can help you ensure you’re being charged properly and can increase your bottom line as you work to grow your business.

What is Oversized?

The first step in making sure you are being charged correctly is to know what constitutes an oversized package. First off, if your is over 20 pounds, that makes it simple — anything weighing more than that is considered oversized. If your box weighs less than 20 pounds, compare its measurements to the following criteria:

  • Longest side: 18 inches or less
  • Medium side: 14 inches or less
  • Shortest side: 8 inches or less

If even one side of your box exceeds the measurement denoted above for the corresponding side, it will be classified as ‘oversized’ and charged accordingly.

Storage Fees

Amazon determines its storage fees based on the size of the product in question, but it may not work quite the way you think. You will actually be charged less per cubic foot for an oversized product than for a standard size. This is for two reasons: one, Amazon doesn’t want to overly discourage the selling of large items, especially when shipping for those items is already higher. Two, space consumption aside, it is actually much easier to store large items than small ones. Large items can generally be organized easily, while storing a bunch of small items can be like a game of Tetris — a difficult task in warehouses as large as those Amazon manages.

The fees Amazon charges for both storing and shipping products of different sizes and weights vary throughout the year, but the big thing you need to be aware of is what size category your products fall into. Read more here to narrow down which category each of your products falls into.

Invoice Insanity

So now you know what size category your products fall into — what do you do with that knowledge? Simple: check Amazon’s work.

When you receive an invoice from Amazon, take the time to scan down your products list to look for any categorized as oversized. Alternatively, if the majority of your items are large, it may make more sense for you to look for ‘standard-sized’ items. Either way, check their categorizing against your own measurements to make sure you’re paying the proper fees. While the difference of a few cents per square foot may not seem like much, it can add up quickly if you keep a large inventory on hand for high-volume sales. Not only that, but if you go too long without checking your invoices, a mistakenly-categorized product can hang around in the wrong price bracket for months, causing the incorrect fees to rack up quickly.

Mistakes by Amazon are relatively rare, but in any operation as large as this one, it’s bound to happen occasionally. In this particular case, stories abound on the Amazon forums of boxes being categorized incorrectly, so it’s worth your time to check to make sure you aren’t being overcharged.