How to Calculate Amazon FBA Profit (No Guessing)

Most sellers don’t lose money on Amazon because their product is bad. They lose because they can’t answer one question fast, accurately, and consistently: “What’s my profit per unit right now?” If you can’t compute that in under two minutes, you’re flying blind on pricing, reorder decisions, and whether to push more inventory into FBA.

This is the execution-first way to calculate Amazon FBA profit - and to systemize it so you’re not rebuilding spreadsheets every time Amazon tweaks fees or your supplier raises costs.

The only Amazon FBA profit formula you need

At the unit level, profit is simple: what you collect minus everything it costs to deliver that unit to the customer.

Amazon FBA Profit (per unit) = Selling price - total per-unit costs

Where total per-unit costs includes Amazon fees, your product cost, shipping into Amazon, and any operational costs you choose to allocate per unit (returns, prep, software, VA time). If you’re calculating at the order level, you’ll also include gift wrap or other order-specific adjustments - but most sellers should start with per-unit.

To make this repeatable, treat it like a checklist of cost buckets. Miss one bucket and your “profit” becomes a fantasy.

What counts as “revenue” in an FBA profit calculation

Use the number that hits your business after discounts. In practice, that means your actual selling price (the price the customer paid, excluding sales tax you don’t keep). If you run coupons, price promos, or lightning deals, those reduce the effective price and must be reflected.

Also decide whether you’re calculating based on your target price (planning) or your realized price (after the fact). Planning is for go/no-go decisions. Realized is for operational control.

The cost buckets that determine real FBA profit

Amazon referral fee

This is usually a percentage of the selling price, and it varies by category. If your product sells for $30 and the referral fee is 15%, that’s $4.50. If your category rate changes, your margin can evaporate quickly, so don’t hardcode old assumptions.

FBA fulfillment fee

This is Amazon’s pick, pack, and ship fee, generally driven by size tier and shipping weight. It’s not the same as the referral fee, and it’s often the biggest line item after your product cost.

Monthly storage (and aged inventory)

Storage is where “I’ll just send more inventory” becomes expensive. Storage is charged per cubic foot, and it rises in peak periods. Aged inventory fees can hit hard when items sit.

If you’re calculating profit per unit for a fast-moving SKU, you can allocate storage as a small per-unit cost based on average monthly storage divided by units sold. If you’re sitting on inventory, you need a separate metric: profit minus carrying cost. Same product, totally different decision.

Inbound shipping to Amazon (and receiving issues)

Inbound freight is real COGS. Whether you ship cartons by UPS or send pallets via LTL, you need an average inbound cost per unit.

A practical approach: take the total shipping invoice for a shipment and divide by the units received. If Amazon splits shipments, track each leg so your “inbound per unit” isn’t understated.

Product cost (landed cost, not supplier quote)

The supplier’s unit price is not your unit cost. Your landed unit cost should include packaging, labeling, inserts, and any per-unit prep you pay for. If you import, include duties and freight forwarder charges.

When your product cost is wrong, your entire business is wrong. Tighten this first.

Returns and reimbursements (net them properly)

Returns are the silent killer in categories with fit, taste, or high defect rates. Amazon will refund customers, you may get the item back in sellable or unsellable condition, and you may receive reimbursements that offset part of the loss.

For clean math, treat returns as a returns rate multiplied by an average return loss. Example: if 6% of orders return and each return costs you $8 on average after any recovery, your expected return cost per unit sold is $0.48.

This is more accurate than pretending returns don’t exist and then wondering why the bank balance feels tight.

Prep, labeling, and compliance

If you pay a prep center or your supplier for FNSKU labels, polybagging, bubble wrap, or carton requirements, that’s a per-unit cost. Even if it’s “only” $0.30, that’s meaningful at scale.

Software and operational overhead (optional, but smart)

Strictly speaking, profit per unit can exclude overhead. But operators who scale cleanly allocate overhead so they can see contribution margin versus true net.

If you use tools for repricing, inventory planning, bookkeeping, or customer service, you can allocate a per-unit overhead cost: total monthly software + operations costs divided by monthly units sold.

This is especially useful if you run a multi-platform ecosystem where your team supports Amazon plus Shopify and off-platform traffic. The overhead is real, and ignoring it makes expansion decisions sloppy.

A worked example: calculate Amazon FBA profit per unit

Let’s say you sell a product for $29.99.

• Referral fee (15%): $4.50
• FBA fulfillment fee: $5.10
• Product landed cost: $8.40
• Inbound shipping to Amazon: $0.75
• Storage allocation: $0.20
• Returns allowance: $0.48
• Prep/labels: $0.30

Total per-unit costs = 4.50 + 5.10 + 8.40 + 0.75 + 0.20 + 0.48 + 0.30 = $19.73

Profit per unit = 29.99 - 19.73 = $10.26

Now compute your margin metrics:

• Gross margin % = 10.26 / 29.99 = 34.2%
• ROI on product cost (common for inventory decisions) = 10.26 / (8.40 + 0.75 + 0.30) = 10.26 / 9.45 = 108.6%

Notice what happened: margin and ROI tell different stories. Margin helps you compare across products. ROI helps you decide where to deploy cash.

How to calculate Amazon FBA profit when pricing changes daily

If you compete in a category where the price moves constantly, you need two numbers:

1. Profit at today’s price (operational reality)
2. Profit at your floor price (risk control)

Your floor price is the lowest price you’re willing to sell at without bleeding. Build it backwards:

Floor price = total per-unit costs + desired minimum profit per unit

If your total costs are $19.73 and you require $6 profit per unit, your floor price is $25.73. If the Buy Box price drops below that, you don’t “hope it comes back.” You either improve costs, shift strategy, or stop replenishing.

The two hidden traps that wreck “profit” calculations

Trap 1: Mixing cash flow with profit

Paying for inventory is a cash event. Profit is recognized when the unit sells. If you look at your bank account after a big reorder and think you’re unprofitable, you’ll make panic decisions.

Track both: profit per unit (economics) and cash cycle (survival). Sellers who scale control the gap between when cash leaves and when it comes back.

Trap 2: Ignoring inventory health

A SKU with great profit per unit can still be a terrible business if it sits and racks up storage, gets stranded, or ages into penalty fees. Profit calculations must be paired with velocity metrics like sell-through and weeks of cover.

Build a profit system you can delegate (and trust)

You don’t need to be the human calculator. You need a system that outputs a weekly profit snapshot per SKU and flags risk before it becomes expensive.

Here’s the clean workflow: one sheet with inputs, one sheet with outputs. Your VA updates inputs weekly. You review outputs in 10 minutes.

Your inputs should be limited to numbers that actually change:

• Current selling price (or weekly average)
• Amazon fees pulled from your reports
• Latest landed cost from supplier invoices
• Inbound shipping cost per shipment
• Storage total for the month (allocated)
• Returns rate and average loss (updated monthly)

Lock the formulas. Don’t let a VA “improve” the math. Your job is to define the structure, then delegate updates.

If you want a stronger operating rhythm, build a simple rule: any SKU below your minimum profit per unit or below your minimum margin triggers a decision within 48 hours - raise price if the market allows, negotiate costs, improve packaging to reduce returns, or pause replenishment.

For more execution-heavy playbooks like this, WAH Academy publishes operator-focused resources at https://resource.wah-academy.com.

How this ties into multi-platform growth

When you know your Amazon FBA profit per unit, you can make smarter ecosystem decisions. You can send off-platform traffic from Meta or influencers to a Shopify store for testing, then move proven winners into FBA for scale. Or you can use Shopify to protect your margin when Amazon pricing gets aggressive.

The point is control. Profit math gives you the confidence to expand without guessing, because you know what each sale funds: more inventory, more delegation, and more leverage.

Your next move is simple: calculate profit per unit for your top three SKUs today, set a floor price for each, and hand the weekly update task to someone else. The founder’s job is to make decisions - not to babysit spreadsheets.