ROI calculation for Google Ads can be tricky. The platform offers many useful measures for e-commerce websites using Google Ads.
The most important measure is Value/Cost. This shows the dollar value you get back for every dollar you spend.
Example: A Value/Cost of 5 means that for every $1 spent on ads, you get $5 in value (revenue) back.
This measure is very useful for checking overall performance and individual campaign performance. However, looking at campaign performance can be complicated because of a process called attribution.
🧩 Understanding Attribution
Attribution is how the conversion (like a purchase) and its total value are credited or "given" to different ads and campaigns. This is important because most customers click on multiple ads or visit the site multiple times before buying.
There are two main levels of attribution:
1) The Global Level (Channels):
This is for websites that use more than one marketing channel to get customers (like Google Ads, Facebook Ads, email, and organic search).
Attribution helps you decide how to split your budget among these different channels. A good attribution model will make sure you put more money into the channels that bring the best results.
If you don't track this correctly, you might spend money on channels that aren't working well.
2) The Platform Level (Campaigns):
This determines how the value of an order is split up among the different campaigns within a single platform (like Google Ads).
This helps marketing managers know which specific campaigns are performing well so they can increase spending on the good ones and stop the bad ones.
Google Ads has a feature that lets you set a "Target ROI" for bidding. In reality, reaching this exact target is rare. Often, the Target ROI setting is just another number that doesn't truly reflect your real profit.
For now, we will focus on platform-level attribution. Global attribution (figuring out which channel gets credit) is very difficult and is usually handled by the marketing department.
Google Ads recommends using "Data-Driven Attribution" to solve the attribution problem inside its platform.
✅ The Ideal Scenario
The goal is to have an attribution model that helps you optimally split your budget so that you get the best possible ROI from all channels and campaigns. Without knowing your true ROI, you can't be sure which channel or campaign is truly the most profitable.
💡 A Better Way to Measure ROI (The Simple Case)
Let's look at the simple scenario where Google Ads is your only marketing channel (or if other channels bring in very few orders, say less than 5% of traffic). In this case, your main decision is simply how much to invest in Google Ads.
We propose a better way to measure your overall ROI than just relying on the Value/Cost number inside Google Ads.
The Solution: Use Google Analytics E-commerce Data.
Instead of using the revenue value reported by Google Ads, we suggest using the Total Sales Value from Google Analytics to calculate your ROI.
Why is this better?
The main reason is that the sales value in Google Analytics is much closer to the real number of sales and orders on your website than the number reported by Google Ads. Google Ads data is often more conservative (lower) than the real sales figures.
⚙️ How to Calculate the Alternative ROI
📈 Improving the Measurement
To get a true ROI, you should use margin instead of sales value.
If your Google Analytics e-commerce setup tracks the profit margin for each order, you can use this for the most accurate calculation:
This calculation truly represents your Return on Investment (the profit you made after paying for the ads).
You can also change the top number (the "Return") to align with your business goal:
Goal: Increase sales >>> Use Total Sales Value / Cost
Goal: Increase orders >>> Use Total Number of Orders / Cost
Goal: Increase market share >>> Use Number of New Customers / Cost