Return on Ad Spend (ROAS)
Return on ad spend, or ROAS, is revenue attributed to advertising divided by the cost of that advertising. It is the most common measure of ad performance because the ad platforms calculate and report it automatically. The number covers attributed revenue and ad cost only. It leaves out cost of goods, fulfillment, returns, and repeat purchases, so a campaign's ROAS and its profitability can move in different directions.
How it actually works
The formula is revenue divided by ad spend. Spend $1,000 and return $5,000 in attributed revenue, and the ROAS is 5:1. The platforms report it pre-calculated: Meta Ads Manager labels it "Purchase ROAS," and Google Ads reports conversion value divided by cost. In both cases the revenue figure comes from a tracking pixel, a piece of code installed on the advertiser's site. When someone who saw an ad later buys, the pixel reports that sale to the platform, and the platform counts the revenue as ad-driven.
Two things are missing from the number. First, it compares ad cost to revenue rather than to profit: cost of goods, fulfillment, returns, and customer longevity are all outside the calculation. The correction is a one-line identity: breakeven ROAS equals 1 divided by the contribution margin rate, because each dollar of attributed revenue carries only its margin toward covering the ad dollar that bought it. At one company with a 20% product margin, that identity puts breakeven at exactly 5:1, so the campaigns reporting a 5:1 ROAS were selling the product at a loss once the other costs were counted, while the dashboards presented 5:1 as strong performance. Any ROAS target set without computing that breakeven first is a target chosen without knowing where losing money begins. Second, the revenue may not be incremental. The platform records every tracked purchase that followed an ad, including purchases from buyers who would have bought without it.
These gaps affect budget allocation. Campaigns that reach buyers close to a purchase report the highest ROAS, so they receive more budget. Campaigns that create new demand convert later and report lower ROAS, so they lose budget first. Over the following quarters, top-of-funnel demand thins, acquisition cost rises, and teams often attribute the rise to market conditions when the cause was the allocation rule. The check against all of this is the marketing efficiency ratio, total revenue divided by total ad spend: it is the only ad-efficiency metric that reconciles to the P&L, because both of its inputs come from the financial statements rather than from a platform's attribution model, so when platform-reported ROAS rises while MER falls, the platforms are reassigning credit for existing sales rather than creating new ones.
In practice
A campaign's ROAS and its profitability can point in opposite directions. At Old School Labs, where our founder served as CMO, revenue grew 87% in ten months. During that period the most profitable cohort in the business came in at a 0.6 ROAS. Margin on that product was high and its customers returned, so the cohort outpaced the second most profitable cohort by five times. Judged on ROAS alone, that campaign would have been cut. This does not mean a low ROAS is good. It means ROAS is a leading indicator of campaign direction, read alongside margin and payback period, and it does not answer whether the campaign made money.
Where we come in
We build measurement systems that track contribution margin and lifetime value alongside platform-reported revenue, so campaigns are judged on profit. This is the approach we used in the Potbelly turnaround, where efficiency was proven at level budget before the budget was scaled.
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Related terms
- PPC (pay per click)
- An advertising model where the advertiser pays per click, not per impression. It is the billing model behind Google Ads and most search advertising.
- Paid media
- Any channel where placement is purchased, such as search, social, and display. It is distinguished from owned media (the company's site and email list) and earned media (unpaid coverage).
- Media buying
- Purchasing ad placement, negotiating rates, and allocating budget across channels.
- Channel management and channel mix
- How budget is split across channels, and the resulting allocation. A buyer typically crosses several channels before purchasing, so optimizing each channel in isolation can misallocate the total.
- Cost per click (CPC)
- Spend divided by clicks. It measures the price of a click and contains no information about whether the click led to a sale.
- Cost per acquisition (CPA)
- Spend divided by conversions. Closer to CAC than ROAS is, but it still excludes margin and repeat purchase.
- Push and pull strategy
- A pull strategy reaches people already searching for a solution; a push strategy reaches people who are not searching yet. Pull campaigns report higher ROAS because their buyers convert sooner, while push campaigns create demand that converts later.
- Marketing efficiency ratio (MER)
- Total revenue divided by total ad spend across every channel. Because both inputs come from the financial statements, it is the only ad-efficiency metric that reconciles to the P&L, and it requires no attribution model at all.
- Breakeven ROAS
- The ROAS at which a campaign neither makes nor loses money: 1 divided by the contribution margin rate. At a 50% margin the breakeven is 2:1; at a 20% margin it is 5:1. It is the number a ROAS target has to be set against.
- Goodhart's Law
- Once a metric becomes a target, it loses its value as a measure. The observation is economist Charles Goodhart's (1975); the popular phrasing, "when a measure becomes a target, it ceases to be a good measure," is anthropologist Marilyn Strathern's. Applied to ROAS: when a team optimizes for the number, the number no longer reflects the state of the business.