ROAS, or return on ad spend, is a ratio that measures how much revenue an advertising campaign generates for every dollar spent on it.
ROAS measures revenue per ad dollar, but hides more than it shows
How ROAS is calculated
The formula is straightforward:
ROAS = Revenue attributed to ads / Ad spend
If a campaign spends $5,000 and the platform attributes $20,000 in revenue to it, the ROAS is 4x (or 400%).
ROAS is reported by every major ad platform: Meta Ads Manager, Google Ads, TikTok Ads, Pinterest Ads, and others. It is the default efficiency metric for performance marketing and appears in almost every paid advertising dashboard.
Why ROAS is useful
ROAS is easy to calculate and universally understood across marketing teams and agencies. It gives a quick read on campaign efficiency and is useful for comparing the relative performance of campaigns, ad sets, or creatives within a single platform.
If you are running ten Facebook campaigns and want to know which ones are generating the most revenue per dollar spent, ROAS is a reasonable starting point. Within a single platform, using the same attribution methodology, it enables like-for-like comparisons.
Why ROAS is often misleading
The number in the numerator, attributed revenue, is not the same as incremental revenue.
Attributed revenue counts all conversions that occurred within the platform's attribution window after someone interacted with the ad. This includes conversions that would have happened without the ad: customers who already intended to buy, organic demand captured by a retargeting campaign, and sales that would have come through direct or organic search.
There are three specific ways this creates misleading numbers.
Attribution overlap. Multiple platforms count the same conversion. If a customer sees a Facebook ad and a Google ad before buying, both platforms attribute the sale to themselves. Your total attributed revenue across platforms can easily exceed your actual revenue by 30-60%.
Generous attribution windows. Meta's default window attributes conversions for 7 days after a click and 1 day after an impression. Google's default click window is 30 days. These windows capture many conversions that had nothing to do with the ad exposure, especially from audiences with high organic purchase intent.
You cannot compare ROAS across platforms. A 4x ROAS on Meta and a 4x ROAS on Google are not the same thing. They use different attribution methodologies, different window lengths, and different definitions of what counts as a conversion event. Cross-platform ROAS comparisons are meaningless.
ROAS and profit are not the same thing
A 4x ROAS sounds excellent. Whether it is profitable depends entirely on your gross margin.
If your product has a 25% gross margin, a 4x ROAS means you generated $4 in revenue for every $1 in ad spend. After production costs, your gross profit is $1 per $1 spent on ads. You are at breakeven, not growing.
If your product has a 60% gross margin, a 4x ROAS means $2.40 in gross profit per $1 of ad spend, after production costs. That is genuinely profitable.
The minimum viable ROAS for a profitable campaign is 1 divided by your gross margin. For a 25% margin product, you need at least 4x ROAS to break even on the media spend. For a 50% margin product, you need at least 2x.
ROAS vs. iROAS
iROAS, incremental return on ad spend, measures revenue only from conversions your ads actually caused. It requires an incrementality test to calculate.
For most retargeting campaigns, iROAS is significantly lower than reported ROAS, often 2-4x lower, because retargeted audiences already have high organic purchase intent. A campaign showing 8x ROAS with 25% incrementality has an iROAS of approximately 2x. That may still be above your breakeven threshold, but it is a very different picture.
For cold audience prospecting campaigns, the gap between ROAS and iROAS tends to be smaller, because cold audiences have lower organic purchase intent.
ROAS vs. MER
MER, Marketing Efficiency Ratio, is total business revenue divided by total ad spend, using backend data rather than platform attribution. It does not rely on attribution models, does not double-count across platforms, and is not subject to attribution window choices.
ROAS is a channel-level, attribution-dependent metric useful for campaign optimization. MER is a business-level, attribution-free metric useful for understanding overall marketing efficiency. For strategic budget decisions, MER is more reliable. For optimizing within a campaign, ROAS is more actionable.