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The FBA Revenue Calculator will tell you whether a product is profitable. It won’t tell you the whole story.

Plug in your numbers and you’ll get an estimate built on fulfillment fees and referral fees. What it typically leaves out: inbound placement fees, aged inventory surcharges, low-inventory-level fees, returns processing charges, and the compounding effect of any inventory that sits longer than expected.

For many sellers, the difference between the calculator estimate and the actual monthly bill is where their margin went.

This guide covers the full fee stack, flags where sellers consistently lose money they didn’t plan for, and shows you how to run a real margin calculation before you send a single unit to a fulfillment center.

The Fee Stack: What Amazon Actually Charges

FBA fees fall into four logical groups. Most sellers know the first two. The third and fourth are where surprises happen.

Fulfillment Fees

These are the core per-unit charges covering picking, packing, shipping, and customer service for every order Amazon fulfills on your behalf. The fee depends on your product’s size tier and shipping weight.

For standard-size products, fees start in the low-to-mid single digits for small standard items and scale up through large standard tiers based on weight and dimensions. Products priced above $50 carry somewhat higher rates reflecting the additional service requirements Amazon applies to higher-value items. Items under $10 fall under the Low-Price FBA structure, which offers reduced rates for qualifying products. Use the FBA Revenue Calculator in Seller Central to get exact figures for your specific size tier and price point.

Oversize items carry meaningfully higher fulfillment fees due to the additional handling involved. Special oversize items can reach $150 or more per unit.

Two important notes for 2026: fulfillment fees increased in January, with the size of the increase depending on your price band. Items under $10 are up approximately $0.12 per unit. Most mid-range products in the $10–$50 band are up around $0.25 per unit. Products priced above $50 see steeper increases, up to $0.51 per unit for small standard items in that range. Check your specific size tier and price band in Seller Central for exact figures.

And as of January 1, 2026, Amazon eliminated its FBA prep and labeling services entirely. Units arriving at fulfillment centers must now be fully prepped and labeled before they ship. Sellers who previously paid Amazon’s prep fee as a convenience are now responsible for handling this upstream, either in-house, through their supplier, or through a third-party prep center.

Storage Fees

Amazon charges monthly storage fees based on the daily average cubic footage your inventory occupies in their fulfillment centers. The rate is seasonal.

Off-peak months (January through September): $0.78 per cubic foot for standard-size items, $0.56 for oversize. Peak months (October through December): $2.40 per cubic foot for standard-size, $1.40 for oversize. That’s a 3x jump from off-peak to peak for standard items. If you’re sending large quantities of inventory in September to prepare for Q4 and it sells slower than projected, you pay peak storage rates on units that weren’t supposed to be there.

Referral Fees

Every sale generates a referral fee, which is a percentage of the total selling price including any shipping or gift wrap charges. Rates vary by category and currently range from 8% to 45%, with most categories falling between 8% and 15%.

Referral fees are unavoidable and category-specific. Check Seller Central for your category’s current rate before calculating margins. A product in a category with a 17% referral fee has a materially different margin profile than the same product in an 8% category.

The Surcharge Tier

This is where most margin calculations break down. Four surcharges apply under common circumstances, and many sellers don’t account for any of them.

Aged inventory surcharge. Amazon applies an escalating surcharge to inventory stored longer than 180 days, in addition to regular monthly storage fees. The surcharge increases through multiple tiers as inventory ages, reaching $6.90 per cubic foot (or $0.15 per unit, whichever is greater) at 365 days and beyond. The current rate schedule for each aging band is in the Aged Inventory Surcharge report in Seller Central. The critical operational point: this replaced the old long-term storage fee structure, which didn’t trigger until 365 days. The effective threshold is now roughly six months, not a year.

Low-inventory-level fee. If your FBA inventory drops below 28 days of historical sales coverage, Amazon charges a per-unit fee on every unit shipped, ranging from $0.32 to $0.97 depending on size tier. The fee is designed to push sellers toward maintaining adequate stock depth, but for brands managing cash flow carefully, it creates a tension between tying up capital in inventory and paying a penalty for running lean.

Returns processing fee. As of mid-2024, Amazon charges a returns processing fee for categories with return rates above a category-specific threshold. Apparel and shoes are charged per returned unit with no threshold. For everyone else, the per-unit fee ranges from $1.78 to $157.35 depending on size and weight. Categories with naturally high return rates — electronics and apparel especially — carry meaningful exposure here.

Inbound defect fee. When units arrive at fulfillment centers non-compliant, Amazon now charges a consolidated inbound defect fee averaging $0.60 per unit. With the elimination of Amazon’s prep services, this fee has more opportunity to apply. Getting prep right upstream is cheaper than paying for errors at the fulfillment center.

Where Sellers Actually Lose Money

Three patterns account for most of the unplanned fee exposure we see across accounts.

Aged inventory surprises. The 181-day surcharge threshold catches sellers who budgeted against the old 365-day rule. A product that sells steadily but not quite fast enough can sit for six months before a seller realizes they’re accumulating surcharges on top of storage fees. The math compounds quickly on bulky items with low sales velocity. Running a monthly aged inventory audit isn’t optional for brands with any product that turns slower than 60 days.

Low-ASP margin compression. For products in the low price range, the fee stack can be brutal. Add a 15% referral fee, a fulfillment fee, monthly storage, and inbound placement fees, and a $12 product can be left with almost nothing before you account for cost of goods and advertising. The Revenue Calculator makes this look survivable. A complete fee stack calculation often doesn’t. Run every low-ASP SKU through the full calculation before committing inventory.

Inbound non-compliance under the new prep rules. Since Amazon ended its prep and labeling services in January 2026, sellers who previously outsourced that step to Amazon now need a reliable alternative. Inbound defect fees aren’t catastrophic per unit, but they’re entirely avoidable, and at scale they add up. More importantly, non-compliant shipments can delay inventory becoming available for sale, which creates a stockout risk that costs more than the defect fee itself.

How to Calculate Your Real Margin

The FBA Revenue Calculator is a useful starting point and a poor finishing point. It typically excludes inbound placement fees, aged inventory risk, returns processing exposure, and low-inventory-level fees.

Here’s the full calculation to run before committing a product to FBA:

Start with your selling price. Subtract the referral fee for your category. Subtract the fulfillment fee for your size and weight tier. Subtract your estimated monthly storage cost (unit cubic footage × storage rate × expected weeks in inventory). Subtract an estimate for inbound placement fees. Add a reserve for returns processing if you’re in a high-return category. What remains before subtracting your cost of goods and ad spend is your actual pre-advertising net.

If that number doesn’t leave room for a profitable ad spend, the product isn’t ready for FBA. The Revenue Calculator showing green doesn’t change that.

For more precise projections, pull the FBA Fee Preview report in Seller Central, which applies current fee rates to your specific ASINs.

Managing FBA Fees as a Business System

The sellers who manage FBA fees well aren’t doing anything complicated. They’re doing a few things consistently.

They audit aged inventory monthly and act on anything approaching 150 days, before the surcharge tier kicks in. They run full fee stack calculations on every new SKU before launch, not after. They maintain inventory depth calibrated to at least 28 days of sales history to avoid low-inventory-level fees. And since January 2026, they’ve established a reliable prep workflow so inbound defect fees don’t erode margins on every shipment.

In our experience, FBA tends to work well financially for products with room in their margins to absorb the full fee stack. The economics get difficult for low-ASP products — and the only way to know which side of that line your SKU sits on is to run the complete calculation before you send inventory, not after you’ve looked at your first monthly settlement report.

FBA remains one of the most efficient fulfillment systems available to Amazon sellers. The fees are manageable when you understand the full structure. When you don’t, they’re a slow drain that doesn’t show up obviously on any single report but accumulates steadily across your P&L.

How Canopy Management Can Help

Managing FBA fees at the SKU level, across a catalog of dozens or hundreds of products, is one of the tasks that most commonly slips when internal teams are stretched thin. Canopy’s brand managers run regular fee audits, flag inventory approaching aged surcharge thresholds, and build FBA cost structure into launch decisions before a product goes live.

If you want a clear picture of where your current FBA fees stand and where you’re leaving margin on the table, start with a free account audit.