Free tool

ACoS calculator

Enter your ad spend and the sales those ads generated to see your ACoS and ROAS instantly. Runs in your browser — nothing is stored, and it works for any currency.

Last updated: June 2026

How do you calculate ACoS?

ACoS (Advertising Cost of Sales) is your ad spend divided by the sales those ads produced, as a percentage: ACoS = (ad spend ÷ ad sales) × 100. For example, $22 of spend that drives $111 in sales is a 20% ACoS — the same as a 5.0 ROAS. A lower ACoS means your ads worked harder for each dollar.

Why it’s trustworthy

  • Official Amazon APIs OAuth only — no scraping, no password sharing
  • 21 Amazon marketplaces North America, Europe and the Far East
  • You approve first Preview every change before it goes live

Your ACoS

20.0%

Equivalent ROAS

5.0×

Calculated in your browser. Currency-neutral — enter whatever currency your reports use.

How to read your ACoS

ACoS on its own is neither good nor bad — it only matters relative to your margins. These three reference points help you judge it.

Compare to break-even

Your break-even ACoS is the margin left after product cost and Amazon fees. Stay below it and each advertised sale is still profitable. Work it out on the break-even ACoS calculator.

Break-even ACoS calculator →

ACoS vs TACoS

ACoS only covers advertised sales. TACoS (Total ACoS) compares ad spend to your whole revenue, including organic — a better gauge of overall efficiency as you scale.

Lower is not always better

A very low ACoS can mean you are under-investing and leaving sales on the table. The aim is the most profit, not the lowest ACoS — sometimes a higher ACoS that wins more volume is worth more.

Knowing your ACoS is step one. Lowering it is the work.

A calculator tells you where you stand today. Moving the number means combing search-term reports for waste, trimming bids on targets that do not convert, and shifting budget to what does — every week, across every campaign. AIAdKing does that nightly on the official Amazon Ads API, logging a reason for every change and previewing it in shadow mode before anything goes live.

See exactly how it cuts wasted spend on the lower-ACoS-automatically page, or read the step-by-step method in the lower-ACoS guide.

Inside the panel

The same maths, running on your own numbers

A calculator answers one scenario at a time. In the panel the projection is carried from your actual month-to-date pace, with the spend scenarios sitting next to it.

Stock cover caps the aggressive end, because spending into a SKU that runs out mid-month buys nothing.

AIAdKing → Ads → Forecasts

Forecasts

Where the month is heading, and what changes if you spend more or less on ads.

MTD spend

$803

10 days actual

MTD sales

$3,278

24.5% ACoS

Projected spend

$2,409

at $80.30/day

Projected sales

$9,834

24.5% ACoS · 4.08× ROAS

What happens if I change my budget?

Drag the slider — the projection updates instantly.

Daily ad budget $80.30/day
0.5×1× (now)3×10×

Stock cover caps the aggressive scenarios — 4 SKUs would run out before month end at 3× spend.

ACoS calculator — FAQ

How do you calculate ACoS?
ACoS (Advertising Cost of Sales) is your ad spend divided by the sales those ads generated, shown as a percentage: ACoS = (ad spend ÷ ad sales) × 100. If you spent $22 on ads that produced $111 in sales, your ACoS is 20%. A lower ACoS means each dollar of ad spend brought in more sales.

What is the difference between ACoS and ROAS?
They are two views of the same numbers. ACoS is spend ÷ sales (lower is better); ROAS (Return on Ad Spend) is sales ÷ spend (higher is better). A 20% ACoS is the same as a 5.0 ROAS. This calculator shows both so you can use whichever your team prefers.

What is a good ACoS on Amazon?
A good ACoS is any figure below your break-even ACoS — the point where an advertised sale still makes a profit after product cost and fees. That break-even depends on your margins, so there is no single universal number. Sellers with high margins can run a higher ACoS profitably; thin-margin products need a lower one.

Does this calculator store my numbers?
No. The ACoS calculator runs entirely in your browser — nothing you type is sent to a server or saved. It is a quick reference tool, not connected to your Amazon account.

How does AIAdKing help lower ACoS?
AIAdKing harvests negative keywords, trims bids on losing targets and shifts budget toward what converts, every night on the official Amazon Ads API — each change logged with a reason and previewable in shadow mode. It is a flat $29/month with no commission on ad spend. See the lower-ACoS page for the full method.

Stop calculating ACoS. Start lowering it.

Connect your Amazon account and AIAdKing surfaces its first bid-trim and negative-keyword proposals in shadow mode — nothing changes until you approve.

Start free for 14 days

$29/month (or $299/year) after trial. Cancel anytime.