Amazon FBA Storage Volume Calculator

Setting it out

Storage volume is the cubic footage your inventory occupies: units × (length × width × height in inches) ÷ 1,728, using the packaged dimensions as Amazon measures them.

Monthly cost = average daily cubic feet × the rate for the size tier and month. The average is daily rather than end-of-month, so arrival timing matters.

Knowing the cubic footage per unit is also what makes the storage line in a unit economics model calculable rather than guessed.

A concrete case

The 9 × 6 × 2 inch product is 108 cubic inches, or 0.0625 cubic feet. Three thousand units occupy 187.5 cubic feet.

At an off-peak rate around $0.78 per cubic foot that is $146 a month; in the fourth quarter at roughly triple, $440.

Now compare a bulkier product: 14 × 10 × 6 inches is 840 cubic inches, or 0.486 cubic feet, nearly eight times the volume. The same 3,000 units cost $1,137 a month off-peak and $3,420 in peak.

Same unit count, same sales rate, eight times the storage cost. Volume per unit is the single input that decides whether storage is a rounding error or a real line.

What the number hides

Amazon measures the packaged unit including any poly bag and prep, not the product. A product that measures 2 inches bare and 2.4 inches bagged occupies 20% more volume than the spec sheet suggests.

Storage limits are also assessed in cubic feet rather than units, so a bulky product consumes far more of a seller's allowance than the unit count implies.

Where to go from here

Calculate cubic feet per unit at product selection and include storage properly in the unit model. It is the input that makes bulky products quietly unattractive and it is easy to compute from dimensions you already have.

Then use it to plan against restock limits, which are expressed in volume. A catalogue of bulky products hits the limit at a much lower unit count than one of small items.

Volume as a product selection criterion

Small and light wins on every Amazon dimension at once: lower fulfilment fee, lower storage, lower inbound freight, more units within a restock limit, and cheaper removals if the product fails.

That is why so much private label activity concentrates in small products, and why the competition there is fiercest. The categories with easier competition are frequently the bulky ones, precisely because the economics are harder.

The judgement is whether the reduced competition compensates for the worse cost structure. It sometimes does, a bulky product with a real differentiator and few sellers can be an excellent business, but it requires a higher price point to carry the fees, and going into a bulky category with a cheap product is the combination that reliably fails.

Restock limits are expressed in cubic feet, so knowing volume per unit converts an abstract limit into a concrete unit count per product. That makes allocation decisions between SKUs explicit rather than first-come, which matters most in the run-up to a peak.