What is COS (Cost of Sale)?
The COS (Cost of Sale, or cost of sales) is an indicator that expresses the relationship between media spend on a channel and the revenue generated by that same channel, as a percentage. In simple terms, it measures the share of revenue absorbed by acquisition costs. Used in digital advertising, affiliate marketing, and budget management, COS makes it possible to evaluate the effectiveness of a lever: the lower it is, the higher the profitability.
How does COS work?
The COS is calculated using the following formula:
COS = (media spend ÷ revenue generated) × 100
For example, a channel that costs €2,000 and generates €20,000 in sales shows a COS of 10%: in other words, 10% of the revenue is used to finance acquisition. The COS is the logical inverse of ROAS: a ROAS of 4 is equivalent to a COS of 25%.
Two thresholds should be kept in mind: a COS of 100% means that media spend equals the revenue generated — you have therefore gained nothing (equivalent to a ROAS of 1); beyond 100%, the channel costs more than it brings in, and you lose money.
The COS applies just as much to an isolated channel (Search, Social, affiliate marketing) as to an entire media mix. In affiliate marketing, it often corresponds to the commission rate negotiated with partners.
Why is COS important in marketing?
The COS gives an immediate reading of a channel’s profitability and constitutes a management threshold: a team can set a target COS (for example 15%) and reallocate the budget as soon as a lever exceeds it. It facilitates comparison between heterogeneous channels and the defense of budget trade-offs internally.
But a COS is only valuable if the data on which it is calculated is accurate: incomplete media spend or poorly attributed revenue immediately skews the ratio and can lead to poor budget decisions. This is why TrackAd clients rely on 100% of the useful data collected and automatically updated every day, guaranteeing a reliable and truly comparable COS from one channel to another.
COS at TrackAd
TrackAd calculates COS from costs imported from media platforms and actual revenue from the Back Office or CRM. Above all, TrackAd ensures that the revenue from each order is only counted once: this deduplication produces real statistics, whereas self-reported conversions by each platform overlap due to a lack of deduplication. The COS can also be used with an attribution model so that revenue is distributed across the different sources of conversion journeys. The COS thus relies on reliable data, a guarantee of sound budget decisions and an indicator that is always updated and comparable from one channel to another.
Frequently asked questions
How to calculate COS?
The COS is calculated by dividing media spend by the revenue generated, then multiplying by 100. For an investment of €3,000 that produced €30,000 in sales, the COS is 10%.
What is the difference between COS and ROAS?
COS and ROAS measure the same reality from two opposite angles. ROAS expresses the revenue generated per euro spent (ratio), while COS expresses the cost as a percentage of revenue. A ROAS of 5 corresponds to a COS of 20%. COS is often preferred for setting profitability thresholds, ROAS for showcasing performance.
Does COS work without cookies?
Yes. COS is a financial ratio, independent of cookies as such. The real challenge is to accurately measure revenue per channel in a cookieless environment. TrackAd addresses this by combining data from the analytical solution with revenue from the Back Office. Result: real and complete revenue and a reliable COS, regardless of the availability of third-party signals.
What is a good COS?
There is no universal ideal COS: it depends on the sector, margins, and the acquisition model. A high-margin e-merchant tolerates a higher COS than a low-margin retailer. The best practice consists of defining a target COS aligned with the product margin, then managing each lever according to this threshold.
The COS (Cost of Sale) designates the share of revenue dedicated to acquisition expenses on a channel, expressed as a percentage. A key indicator of profitability, it is interpreted inversely to ROAS and only has value if the media data and revenue are correctly reconciled.