Profit, not revenue, per pound of spend
Profit on ad spend is the full name for the metric most marketers know by its abbreviation, POAS. The two terms are interchangeable, and both describe the same shift in thinking: judging a campaign by the margin it contributes rather than the revenue it reports. The calculation is simply gross profit divided by advertising spend, where gross profit is revenue with the cost of goods, fulfilment, fees and returns already stripped out.
That distinction is the whole point. A campaign can move a great deal of revenue while keeping almost none of it, and a revenue-based metric will happily wave it through. Profit on ad spend closes that gap by measuring the money that survives all the way to contribution - the number that actually funds the business rather than the number that looks best in a screenshot.
How profit on ad spend differs from ROAS
ROAS divides revenue by spend and stops there - it never sees margin. That makes it easy to read but dangerous to optimise against, because two campaigns with an identical ROAS can have wildly different profitability once their cost structures are accounted for. Profit on ad spend divides gross profit by spend instead, so a high-revenue, low-margin product no longer flatters the report.
Consider a campaign that earns £40,000 of revenue on £8,000 of spend: a headline ROAS of 5.0 that any team would be pleased with. But if the cost of goods and fulfilment is £24,000, the gross profit is only £16,000, and the profit on ad spend is 2.0. The revenue figure tripled the apparent performance. Knowing the point at which a campaign stops contributing at all is the job of the break-even ROAS, the revenue multiple below which a sale loses money once every cost is counted.
The costs that erode profit
Several layers of cost sit between revenue and profit, and each one pulls profit on ad spend below ROAS. The cost of goods sold is usually the largest - the wholesale or manufacturing cost of what was sold. Then come fulfilment and shipping, which scale with order volume; payment processing fees, typically a few percent of every transaction; and the discounts and promotions used to drive the sale in the first place, which come straight out of margin.
Returns and refunds are the quietest erosion of all. A campaign can look efficient at checkout and then surrender a chunk of its margin weeks later when products come back, complete with reverse shipping and restocking costs. Because none of these costs appear in a revenue-based metric, a campaign optimised purely to ROAS can be steadily eroding contribution without ever showing it. This is also why profit on ad spend pairs naturally with customer acquisition cost, which sets the spend side of the same contribution question.
Why profit on ad spend matters for ecommerce
Ecommerce is where the revenue-versus-profit gap bites hardest. Margins differ sharply between products, discounting is constant, and return rates can be high in categories like fashion. Optimising to ROAS in that environment pushes budget toward whatever drives the most revenue, which is rarely the same as whatever drives the most profit. A bestseller sold at a deep discount can post a beautiful ROAS and a barely positive POAS, while a higher-margin line quietly does the real work.
Switching the target metric to profit on ad spend realigns budget with the bottom line. The catch is that profit, like revenue, runs into diminishing returns as spend scales - the next pound contributes less profit than the last - so the goal is not to maximise POAS on a single campaign but to allocate the whole budget to where the next pound of profit is highest. That is fundamentally a forecasting question, not a reporting one.
How ElenIQ uses profit on ad spend
ElenIQ forecasts the commercial impact of budget changes before any money is committed, so you can see how a reallocation moves profit - not just revenue - across products and channels. By modelling margin alongside response, it keeps the focus on contribution, which is the metric that actually grows the business.
You can pressure-test the relationship between revenue, margin and return directly with the POAS calculator, then forecast a full plan around profit rather than headline revenue with the ad spend forecasting tool.
Related terms
- POAS - the abbreviation for profit on ad spend, the same metric in shorthand.
- ROAS - revenue per pound of spend, the revenue-based metric POAS corrects for margin.
- break-even ROAS - the revenue multiple at which a sale stops being profitable once costs are counted.
- customer acquisition cost - what it costs to win a customer, the spend side of the profit equation.
Frequently asked questions
What is profit on ad spend?
Profit on ad spend, abbreviated POAS, is the gross profit a campaign generates for every pound of advertising spend. Where ROAS measures revenue returned per pound spent, POAS strips out the cost of goods sold, shipping, payment fees and returns first, so the ratio reflects money you actually keep rather than top-line revenue that may carry thin or negative margins.
How do you calculate profit on ad spend?
Calculate gross profit by taking revenue from the ad-driven sales and subtracting the cost of goods sold, fulfilment, payment processing fees and returns. Divide that gross profit by the advertising spend that produced it. For example, £40,000 of revenue with £24,000 of product and fulfilment costs leaves £16,000 of gross profit; on £8,000 of spend that is a POAS of 2.0, even though the ROAS on the same numbers is 5.0.
How is profit on ad spend different from ROAS?
ROAS divides revenue by spend and ignores margin entirely, so two campaigns with identical ROAS can have very different profitability. Profit on ad spend divides gross profit by spend, which means a high-revenue, low-margin product can post a strong ROAS while its POAS is barely above break-even. POAS is the more honest signal for deciding which products and channels to scale.
What costs reduce profit on ad spend?
The main costs that erode profit on ad spend are the cost of goods sold, shipping and fulfilment, payment processing fees, discounts and promotions, and product returns or refunds. Each one sits between revenue and profit, so a campaign can return plenty of revenue per pound while returning very little actual margin once these costs are deducted.
Why does profit on ad spend matter for ecommerce?
Ecommerce margins vary widely by product, and discounting and returns can quietly turn a profitable-looking campaign into a loss-maker. Optimising to ROAS pushes budget toward whatever drives the most revenue, which is not always the most profitable line. Profit on ad spend keeps the focus on contribution, so you scale the products and channels that grow the bottom line rather than just the top line.