ACoS vs TACoS vs ROAS: The Ad Metrics That Decide Your Profit
ACoS is ad spend divided by ad-attributed sales. TACoS is ad spend divided by total sales (organic plus ads). ROAS is ad revenue divided by ad spend, the inverse of ACoS. Your break-even ACoS equals your gross margin: spend more of a sale on ads than your margin and you lose money on that order.
Three metrics, three questions
- ACoS (Advertising Cost of Sale) answers: how efficient is this campaign? It is ad spend divided by the sales that campaign generated, as a percentage.
- TACoS (Total Advertising Cost of Sale) answers: how dependent is my whole business on ads? It is ad spend divided by total sales, organic included.
- ROAS (Return on Ad Spend) answers the same question as ACoS from the other direction: revenue per dollar of ad spend. A 4x ROAS is a 25% ACoS.
The number that matters most: break-even ACoS
Your break-even ACoS is simply your gross margin. If a product carries a 35% gross margin, you can spend up to 35% of the sale on advertising before the order loses money. Spend less and you profit; spend more and you are buying sales at a loss.
Break-even ACoS = gross margin. On a 35% margin product, a 30% ACoS is profitable and a 40% ACoS is not, no matter how good the ROAS looks in isolation.
Why TACoS reveals the real trend
ACoS can look great on a single campaign while your business is still overly ad-dependent. TACoS captures that. A falling TACoS over time is one of the healthiest signals in ecommerce: it means your ads are building organic momentum, so each new sale relies less on paid spend.
Putting it together
Use ACoS to judge and optimize individual campaigns against your break-even. Use TACoS to judge the health of the whole business over months. And always tie both back to net profit: a target ACoS that ignores your true margin is just a vanity number.
Frequently asked questions
Is a lower ACoS always better?
Not necessarily. A very low ACoS can mean you are underspending and leaving sales on the table. The goal is the highest volume you can drive while staying under your break-even ACoS.
How do I convert ROAS to ACoS?
ACoS equals 1 divided by ROAS, as a percentage. A 4x ROAS is a 25% ACoS; a 2x ROAS is a 50% ACoS.
What is a good TACoS?
It varies by stage, but a stable or declining TACoS is the signal to watch. Rising TACoS means the business is becoming more dependent on paid ads.
Related tools & guides
MerchSites tools and guides are written and reviewed by ecommerce practitioners. Calculations are cent-accurate estimations based on reported platform fees and standard formula math.