What is Amazon ACOS?
ACOS (advertising cost of sale) on Amazon is the percentage of ad-attributed revenue consumed by ad spend. Sponsored Products, Sponsored Brands, and Sponsored Display report it in Campaign Manager. It answers a simple question: how much of each sale went to ads?
This is not the math function arccos (inverse cosine). If you searched for a trig calculator, you want a different tool — this page is for Amazon PPC and ecommerce advertising only.
ACOS = (Ad spend ÷ Ad-attributed revenue) × 100
Spend $2,000, generate $10,000 in ad-attributed sales → ACOS = (2,000 ÷ 10,000) × 100 = 20%.
How to calculate ACOS (step by step)
- Pull ad spend from Amazon Ads Campaign Manager for the date range.
- Pull ad-attributed sales — same date range, same attribution window (typically 7-day or 14-day click).
- Divide spend by revenue × 100 — that's your ACOS.
- Compare to your gross margin — is ACOS below your margin? If yes, ads are profitable after product cost.
Worked example: three Sponsored Products campaigns
An Amazon seller runs three campaigns with different ACOS levels. Gross margin is 50% (break-even ACOS = 50%):
| Campaign | Ad spend | Ad-attributed revenue | ACOS | ROAS | Below break-even? |
|---|---|---|---|---|---|
| Exact match (brand terms) | $500 | $5,000 | 10% | 10x | ✅ Very profitable |
| Broad match (category) | $1,200 | $4,000 | 30% | 3.3x | ✅ Profitable |
| Auto-targeting (discovery) | $800 | $1,600 | 50% | 2x | ⚠️ At break-even |
| Total | $2,500 | $10,600 | 23.6% | 4.2x | ✅ Below 50% |
The auto-targeting campaign sits right at break-even (50% ACOS = 50% margin) — every sale's gross profit is consumed by ad spend. The brand terms campaign is extremely efficient (10% ACOS). The overall blended 23.6% ACOS is healthy at this margin. The action: scale exact and broad match budgets; either optimize or cap auto-targeting to keep blended ACOS well below 50%.
What happens when ACOS exceeds break-even
Same seller, but category competition drives CPCs up:
| Scenario | ACOS | Margin | Profit per $100 sale | Status |
|---|---|---|---|---|
| Original (efficient) | 23.6% | 50% | $50 − $23.60 = $26.40 | ✅ Profit |
| Competition up | 55% | 50% | $50 − $55 = −$5 | ❌ Loss per sale |
At 55% ACOS with 50% margin, every $100 in ad-attributed sales loses $5 before overhead. The seller must either lower bids, improve conversion rate on listings, raise prices, or accept that the category is no longer profitable on paid — and shift budget to organic ranking plays.
ACOS vs. ROAS — same math, different view
ROAS is revenue ÷ spend (a multiple). ACOS is spend ÷ revenue (a percentage). They are inverses:
- 20% ACOS = 5x ROAS
- 25% ACOS = 4x ROAS
- 50% ACOS = 2x ROAS
Use the ROAS calculator if you think in multiples; use ACOS if you think in "cents on the dollar" or compare to Amazon's dashboard. See ACOS vs ROAS for a full comparison with conversion tables.
Break-even ACOS
Your break-even ACOS equals your gross margin %. At 50% margin, you break even at 50% ACOS (2x ROAS). Any ACOS below 50% leaves room for profit after product cost; any ACOS above 50% loses money on each ad-attributed sale before overhead.
How to improve ACOS
Lower ACOS (better efficiency) by improving conversion rate on listings, tightening keywords and negative targets, raising AOV through bundles, and cutting spend on campaigns with high ACOS and low volume. Track ACOS alongside total blended ROAS so platform efficiency matches real business growth.