Amazon ACoS Calculator

Stop guessing your bids — whether you sell private-label (FBA), publish books on KDP, or run Merch on Demand. Pick your seller type, enter your numbers, and get your break-even ACoS, a target ACoS for any profit goal, and the maximum CPC bid that still makes money — plus instant ACoS↔RoAS. Your numbers never leave your browser.

1. Product profitability

Your margin before advertising sets the ceiling for everything else.

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Your numbers

Updates as you type.

Profit before ads / unit—
Margin—
Break-even ACoS—
Break-even RoAS—

2. Target ACoS for a profit goal

How much net margin do you want to keep after ad spend?

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Target ACoS—
Target RoAS—

3. Maximum profitable bid

The most you can pay per click and still hit your target ACoS.

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Max CPC bid—

4. ACoS ↔ RoAS converter

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How break-even ACoS works

ACoS (Advertising Cost of Sale) is the share of an ad-driven sale that you spent to get it: ACoS = ad spend ÷ ad revenue. Your break-even ACoS is the point where ad spend exactly equals your profit — and it's simply your profit margin before advertising:

Break-even ACoS = (Sale price − COGS − referral fee − FBA fee − other costs) ÷ Sale price. Spend below it and you profit; spend above it and you lose money on every ad sale.

Example: a $29.99 product with $7 COGS, a 15% ($4.50) referral fee and a $5.50 FBA fee nets $12.99 profit, a 43.3% margin. So your break-even ACoS is 43.3%. Any campaign under that ACoS is profitable.

Three modes: FBA, KDP & Merch on Demand

The maths is identical for everyone — break-even ACoS = your margin per sale ÷ your price — but “margin” means something different depending on how you sell. Pick the matching mode at the top:

ModeYour margin is…Break-even ACoS
📦 FBA / SellerSale price − COGS − referral fee − FBA fee − other costsprofit ÷ sale price
📚 KDP (Books)Your royalty: ~70% of list (eBook, minus delivery) or ~60% of list minus printing (paperback)royalty ÷ list price
👕 Merch on DemandThe royalty Amazon pays you per sale (shown in your dashboard)royalty ÷ list price

KDP authors: a $4.99 Kindle eBook on the 70% plan earns about $3.45 royalty, a 69% margin — so you break even on ads up to a 69% ACoS. Books have fat margins, which is why aggressive ACoS can still pay. Merch sellers: a $21.99 shirt paying a $4.30 royalty breaks even at about a 20% ACoS — thinner, so bids need to stay tight.

From break-even to target ACoS

You rarely want to run at break-even — you want to keep some profit. Your target ACoS leaves room for the margin you want: target ACoS = break-even ACoS − desired net margin. In the example above, to keep a 15% net margin you'd target 43.3% − 15% = 28.3% ACoS.

Turning target ACoS into a bid

Amazon bidding is per-click, but profit is per-sale, so the bridge is your conversion rate:

Max CPC bid = Sale price × Conversion rate × Target ACoS.

A $29.99 product converting at 10% with a 28% target ACoS supports a max bid of about $0.84 per click. Start new keywords here and adjust from real data. Don't know your conversion rate yet? 10% is a reasonable Amazon starting assumption; check your business reports once you have traffic.

ACoS and RoAS quick reference

ACoSRoASReading
10%10.0×Very efficient — likely room to scale spend
20%5.0×Strong for most categories
25%4.0×Common healthy target
33%3.0×Fine if your margins are fat
50%2.0×Break-even only if margin ≥ 50%
100%1.0×Spending your whole sale — launch/rank only

When to run above break-even on purpose

New products often run a high ACoS during launch to buy sales velocity, reviews and organic rank — then tighten bids once they rank and let organic sales carry the profit. The discipline is to do it deliberately with a launch budget, always knowing your break-even so you can measure how aggressive you're being.

Private by design. Your prices, costs and margins are calculated entirely in your browser. This site is static — nothing is uploaded, logged, or shared.

Frequently asked questions

What is a good ACoS for Amazon PPC?

Anything below your break-even ACoS, which equals your pre-ad margin. There's no universal number — a 25% ACoS is great on a 45%-margin product and fatal on a 20%-margin one. Calculate yours above.

How do I calculate break-even ACoS?

It's your margin per sale ÷ your price. For FBA that's (price − COGS − referral fee − FBA fee − other) ÷ price; for KDP and Merch it's your royalty ÷ list price. The calculator does it live in whichever mode you pick.

How does the KDP (books) mode work?

Your margin is your royalty. Choose Kindle eBook (70% or 35% plan) or Paperback/Hardcover, enter the list price (plus delivery or printing cost), and it computes your royalty and break-even ACoS = royalty ÷ list price. eBook royalties are high, so books tolerate higher ACoS than physical products.

How does the Merch on Demand mode work?

Amazon shows your royalty per sale for each design in the Merch dashboard. Enter the list price and that royalty, and break-even ACoS = royalty ÷ list price — the most you can spend on ads per sale before losing money.

What's the difference between ACoS and RoAS?

They're inverses. ACoS = spend ÷ sales (a %); RoAS = sales ÷ spend (a ×). 25% ACoS = 4× RoAS. Lower ACoS / higher RoAS = more efficient.

How much should I bid on a keyword?

Up to sale price × conversion rate × target ACoS. For $30 at 10% CVR and 25% ACoS, that's $0.75 max per click.

Should I run ads at a loss to rank?

Sometimes, during a launch — to gain velocity and reviews — then tighten once you rank organically. Do it on purpose with a budget, knowing your break-even.

Is my cost data sent anywhere?

No. All math runs in your browser; nothing is uploaded or stored.

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