An e-commerce brand's sales journey often doesn't start and end on a single channel. A user might see a product in a Meta ad, search for the brand on Google a few days later, check the price on the website, and place the order through a marketplace.
Reading this journey solely from the ad panel or website sales would be incomplete. In e-commerce, when website, marketplace, and ad data are examined together, it becomes clearer how ad spend reflects in total revenue, which channel completes the sale, and whether the budget genuinely generates more revenue.
Why a Single Data Source Is Not Enough in E-commerce
Google Ads reports ad interactions, Meta Ads reports conversions from its own campaigns, GA4 reports user behavior on the site, and the e-commerce infrastructure reports completed orders. Marketplaces, on the other hand, have separate sales data.
It's not surprising that these systems don't show the same sales figures. While one platform might attribute conversion credit to the same order, another system might prioritize a different channel. The attribution model used, conversion window, and measurement method change the results.
The goal here is not to equalize all figures. First, it's necessary to know what each platform measures, and then compare this data with the company's actual sales results.
What Does Website Data Tell Us?
Website data shows what the user did before purchasing. Where they came from, which product they viewed, whether they proceeded to the cart, whether they abandoned at the payment step, and whether they completed the purchase can all be seen here.
If ad traffic is increasing but sales are not growing at the same rate, it's not correct to immediately deem the campaign unsuccessful. If users are coming to the product page but not adding to the cart, there might be an issue with pricing, product offering, or stock. If add-to-cart rates are high but orders are not being completed, shipping costs, payment options, or the purchase process should be checked.
The conversion rate provides an important clue at this point:
CVR = Number of Purchases / Number of Sessions or Users
If clicks are rising while CVR is falling, it might mean more traffic is coming in, but the incoming users have a weaker propensity to purchase. If CVR is rising while traffic hasn't changed much, part of the revenue increase might be due to the site generating better conversions, not just the ad budget.
Why Should Marketplace Data Be Included in the Analysis?
Even if the website generates strong sales, excluding marketplaces can distort the overall picture. A user who encounters an ad might order the product from Trendyol, Hepsiburada, Amazon, or another platform they shop on, instead of the brand's website.
This sale is not expected to appear as an ad conversion in GA4. Nevertheless, the ad might have played a role in the user discovering the product. As the share of marketplaces in total sales increases, this distinction becomes more important.
Ending the analysis by just looking at the revenue figure on the marketplace side can also be misleading. To see the economic value of the sale, commissions, campaign contributions, shipping, operational expenses, and returns must also be taken into account.
Practically, the following flow can be used:
Gross sales → commission → campaign cost → shipping and operations → returns → net revenue → product margin
The website and marketplace might have generated 500,000 TL in sales in the same month. If commissions and campaign costs are higher in the marketplace, the amount remaining for the company will differ across the two channels. When allocating budget, it's crucial to see this difference rather than just the gross revenue.
Why the ROAS Shown by Ad Platforms May Not Be Sufficient
ROAS shows how much conversion value the platform reports against the ad budget spent.
ROAS = Ad-Attributed Revenue / Ad Spend
If 1,000,000 TL in conversion value is reported for 200,000 TL in ad spend, the ROAS is 5. This metric is functional for comparing campaigns, product groups, or target audiences.
However, the revenue used here is the revenue that the platform's own measurement system attributes to the ad. It does not represent the same thing as the total revenue generated across the company's website, marketplace, and other sales channels.
Instead of immediately increasing the budget when ROAS rises, it's necessary to check whether total sales are moving in the same direction. CPA, number of new customers, marketplace sales, and MER are key metrics that can be used for this control.
How to Read ROAS and MER Together
ROAS primarily describes campaign performance. MER, on the other hand, shows the state of ad investment relative to total e-commerce revenue.
A simple calculation focused on paid media can be done as follows:
MER = Total E-commerce Revenue / Total Paid Media Spend
If the company tracks marketplaces along with its website within total e-commerce revenue, these sales can be included in the calculation. The important thing here is that the calculation method should not be changed from period to period.
| Metric | What It Tells Us |
|---|---|
| ROAS | Revenue reported by the ad platform against spend |
| CPA | Ad budget spent for one conversion |
| CVR | How much of the traffic converts into a purchase |
| MER | Ratio of total revenue to ad spend |
| Total Revenue | General direction of sales volume |
| Net Revenue | Sales value remaining after costs |
For example, suppose Google Ads ROAS has increased from 4.5 to 5.2. If MER has decreased from 6.5 to 5.8 in the same period, and total sales are also falling, it becomes difficult to say that the campaign has become more efficient by only looking at the Google Ads screen.
First, it's necessary to look at where the ROAS increase came from. If branded searches, remarketing campaigns, or existing customers have started to take a larger share, the platform's figure might improve, while the power to generate new sales might not have increased to the same extent.
How to Analyze Website, Marketplace, and Ad Data Together
Instead of trying to achieve the same sales figures across all platforms, it's more useful to compare each data source over the same period and with the same commercial objective.
The analysis can proceed in this order:
- Calculate total sales. Aggregate revenue, orders, and product quantities from the website and marketplaces within the same date range.
- Add ad spend. See the total spend across Google Ads, Meta Ads, and other channels.
- Review campaign performance. Check changes in ROAS, CPA, CPC, CPM, and CTR.
- Examine the website side. Compare traffic, CVR, product views, add-to-cart, and purchase rates.
- Delve into the marketplace. Track gross revenue along with commissions, returns, campaign costs, and, if possible, product margin.
- Compare the overall picture. See how total revenue, MER, and the number of new customers move when ad spend changes.
- Move to the product level. If necessary, repeat the same comparison on a category, SKU, and campaign basis.
An Example Scenario
Let's consider a brand's sales over two weeks. The figures below are created to illustrate the method and are not based on real customer data.
In the first week, let the website generate 800,000 TL and marketplaces 500,000 TL in sales. When ad spend is 200,000 TL, total revenue is 1,300,000 TL, and MER is 6.5.
In the second week, the ad budget is increased to 210,000 TL. While ROAS increases on the ad platform, website revenue also rises to 850,000 TL. However, marketplace revenue drops to 390,000 TL in the same week. Total sales decrease to 1,240,000 TL, and MER becomes approximately 5.9.
It would not be correct to say that the advertising is performing poorly based on these figures alone. A significant product might have gone out of stock in the marketplace, a campaign might have ended, or prices might have changed. Similarly, immediately increasing the budget based on a high ROAS in the ad panel would be a hasty decision.
First, it's necessary to find the reason for the change. When stock, price, product mix, campaign period, and new customer rate are checked, the difference between ROAS and total sales becomes more meaningful.
How to Interpret Interaction Between Channels
A user might see a product for the first time in a Meta ad. A few days later, they might search for the brand name on Google, visit the site, and then purchase the same product from a marketplace.
In this journey, Meta might have introduced the product, Google might have brought the user back to the brand, and the marketplace might have taken the order. Attributing the entire sale to one of these channels oversimplifies the customer journey.
Therefore, an additional question needs to be added to "Which channel made the sale?": What did each channel do in the user's purchase journey? This distinction directly affects budget decisions, especially for brands that run brand awareness investments, remarketing campaigns, and marketplace sales concurrently.
What Decisions Does Joint Analysis Change?
When data is brought together, it becomes easier to understand which channel is truly generating growth. If a campaign that looks good on the ad platform doesn't create the same impact on total revenue, this difference can be noticed earlier.
Suppose ROAS is falling while the number of new customers, total revenue, and MER are rising; then, it might not be correct to cut the budget solely due to the ROAS drop. Conversely, if ROAS is rising but total revenue remains constant, it should be investigated whether the advertising is capturing existing demand rather than creating new demand.
This analysis is particularly useful for the following decisions:
- Google Ads and Meta Ads budget allocation
- Share of brand and non-brand campaigns
- Acceptable CPA level
- Website and marketplace campaign policy
- Product-based ad budget
- Remarketing budget
- Campaign scaling decisions
How Can AdsLuma Support This Process?
Checking Google Ads, Meta Ads, and GA4 data separately is time-consuming, especially for teams managing many brands or accounts. The real challenge is not seeing the data, but understanding how the figures on different screens relate to each other.
In AdsLuma, when ad and analytics data are tracked on the same dashboard, metrics like ROAS and CPA can be compared within the same period. With GA4 and Search Console data added, changes between paid traffic, site behavior, and organic performance can be tracked from the same place.
If marketplace sales are kept in the company's own reporting system, this data can also be included in total revenue and MER calculations. This makes it easier to read the difference between the performance seen on the ad platform and the company's actual sales results.
Why Is It Important to Look at Website, Marketplace, and Ad Data on the Same Table?
Expecting all systems to show the same sales figures in e-commerce performance is unrealistic. Each platform measures a different part and operates with its own reporting logic.
More importantly, it's about being able to see how these different figures relate to total sales and ad investment. When ROAS increases, if total revenue, MER, CPA, number of new customers, and marketplace sales are also examined simultaneously, the campaign's contribution to the business can be interpreted more accurately.
The main benefit for the team emerges here. It becomes possible to determine which channel and which product group the next budget will be allocated to with more robust data, rather than just which channel looks better in the report.
Frequently Asked Questions
Why do ad and sales data differ in e-commerce?
Ad platforms, GA4, and e-commerce systems use different attribution models, conversion windows, and measurement methods. Therefore, the same sale can be reported differently across different systems. Instead of trying to equalize the figures, it's necessary to know what data each source shows and compare them within the same period.
Is ROAS or MER more important?
ROAS shows campaign performance, while MER shows the state of ad spend relative to total revenue. ROAS is more useful for campaign optimization. At the company level, when evaluating budget efficiency, MER, along with total revenue and CPA, provides a more meaningful picture.
Should marketplace sales be included in ad analysis?
If marketplaces have a significant share of total sales, they should be included. A user might discover a product through an ad and complete the order on a marketplace. If this sale doesn't appear in GA4 or the ad platform, excluding marketplace data can incompletely show the total sales change during the ad period.
Why might total sales decrease while ad ROAS increases?
An increase in ROAS can stem from branded searches, remarketing, existing customer sales, or changes in the product mix. If total orders, marketplace sales, or new customer revenue are decreasing in the same period, the ROAS increase might be telling a different story. Therefore, MER and total revenue should also be checked for the same dates.
Which data should be tracked together for e-commerce performance?
Ad spend, ROAS, CPA, CPC, CTR, website revenue, CVR, marketplace revenue, total orders, and MER are a good starting set. For more detailed analyses, new customer rate, returns, commissions, CAC, LTV, product margin, and net revenue can also be added. This way, the impact of the budget on profitability, along with sales, can also be seen.
