Index
What is CAC and how to calculate it
What is marketing ROI and how to interpret it
How to measure performance by channel
The most common mistakes when calculating these metrics
Which KPIs to review every month
How to improve CAC without reducing lead volume
Dealcar and controlling marketing metrics
Frequently asked questions
What is CAC and how to calculate it
CAC (Customer Acquisition Cost) is the average cost you incur to close a sale. It includes everything you invest to get a lead to arrive and buy: portal advertising, Google Ads, Meta Ads, CRM tools, sales team commissions, and any cost directly related to acquisition.
The formula is: CAC = Total marketing and sales spend / Number of sales closed in that period.
A concrete example: if in October you spend 4,500 euros between portals, digital advertising, and sales costs, and close 15 sales, your CAC is 300 euros per vehicle sold. If your average net margin per transaction is 1,400 euros, you allocate 21% of the margin to acquisition. If the margin is 800 euros, you are allocating 37%, which is starting to be a red flag.
CAC is not a good or bad number in itself: it is good or bad in relation to your margin. What is best is to calculate it by channel to know which acquisition source is most efficient.
What is marketing ROI and how to interpret it
Marketing ROI (Return on Investment) measures how much profit each euro invested in acquisition generates. The formula is: ROI = [(Margin generated by sales attributed to the channel - Investment in that channel) / Investment in that channel] x 100.
The result is a percentage. An ROI of 200% means that for every euro invested you recover that euro plus an additional two. A negative ROI means you are losing money on that channel even if you are selling cars.
The most important nuance when calculating marketing ROI is what you include in the numerator. If you use the sale price instead of the net margin, the ROI looks fantastic but does not reflect real profitability. A car sold for 14,000 euros with a net margin of 900 euros and a CAC of 400 euros has a very different marketing ROI depending on whether you calculate based on the sale price or the margin. The only way for the number to be useful is to use it on the margin.
How to measure performance by channel
Overall CAC and ROI are useful, but where business decisions are made is in the breakdown by channel. Not all portals or all campaigns perform the same, and concentrating the budget on what works is the most profitable exercise a dealership can do each month.
Check which portals perform best for selling cars in Spain.
To do this, every lead that enters must have its origin recorded: which portal it came from, whether it came from a Meta Ads campaign, an organic search, or a recommendation. Without that data, calculations by channel are impossible.
The tools that allow this tracking are: UTM parameters in campaign links (to distinguish web traffic by origin), a CRM that records the source channel of each lead until linking it with the sale, and Google Analytics to see web traffic behaviour according to the source.
With those data, you can calculate for each channel: how many leads it generated, how many of those leads converted into sales, how much each lead cost (CPL), and how much each closed sale cost (CAC per channel). Two channels with the same CPL can have very different conversion rates, making their actual CAC completely different.
The most common mistakes when calculating these metrics
The most common is not including all costs. The salary of the salesperson who handles the leads, commissions, the cost of management tools: all of that is part of the acquisition cost. If you only include the portal invoice, the CAC looks low but does not reflect what each sale actually costs.
The second is not correctly attributing leads to their source channel. If a buyer saw the car on AutoScout24 but got in touch via WhatsApp, and in the CRM it simply appears as "WhatsApp", AutoScout24 is left without its attributed sale and its performance looks worse than it is.
See also how to recover cold leads in a dealership.
The third is mixing different periods or campaigns in the same calculation. An investment in portals in one month can generate sales in the following month. If you only look at the month the investment was made, the ROI looks low. Temporal attribution requires defining a reasonable conversion window, usually between 30 and 60 days in the used vehicle market.
The fourth is ignoring leads that come through recommendations or offline. They have a CAC of almost zero and distort the overall average if they are not segmented separately.
Which KPIs to review every month
With data properly recorded, the monthly review takes no more than 20 or 30 minutes. There are six indicators that give the true picture of marketing performance.
Monthly investment by channel is the starting point: how much you have spent on each acquisition source. CPL (cost per lead) by channel tells you how much each contact costs on each platform. Conversion rate by channel shows what percentage of leads from each source ends up buying. CAC by channel combines the previous two to give the actual cost per sale on each platform. The average margin per sale attributed to the channel allows you to calculate the real ROI. And the average time from first contact to closing warns you if a channel is bringing in cold leads that require a lot of sales work before converting.
Read how to manage leads to increase dealership sales.
With those six numbers, you can make concrete decisions: increase investment in the channel with the best ROI, review the strategy of the one with the worst conversion, or simply eliminate those that are not performing.
How to improve CAC without reducing lead volume
Lowering CAC does not mean spending less on acquisition: it means spending better. There are three levers that improve CAC without sacrificing volume.
The first is improving the conversion rate. If the same number of leads generates more sales, the CAC goes down even if the spend remains the same. Responding faster, qualifying the buyer better, and having a structured follow-up process are the factors that have the biggest impact on conversion.
The second is diversifying channels. Relying on one or two portals makes the overall CAC vulnerable to price changes on those platforms. Activating channels with lower CAC, such as email marketing to your existing customer database or remarketing to website visitors, reduces the average CAC without reducing reach.
Read the guide on Meta Ads for dealerships to activate a channel with lower CPL.
The third is build loyalty among current customers. A customer who buys again or who refers an acquaintance has a CAC close to zero. Investing in the post-sales experience and a basic referral programme can generate a growing percentage of sales at minimal cost.
See also how to build a local brand for a dealership.
Dealcar and controlling marketing metrics
To calculate the CAC and ROI of each channel, you need a system that records the source of each lead and links it to the sale it generates. Dealcar centralises leads from all channels (portals, WhatsApp, web, Meta) in a single dashboard, with the source channel recorded from the first contact and linked to the sales file when the transaction is closed.
This eliminates the need to cross-reference data from multiple tools to calculate marketing metrics. If you want to see how it works, request a demo at dealcar.io.
Frequently asked questions
What is a reasonable CAC for a used car dealership?
There is no universal number because it depends on the average margin per transaction and the price segment. As an indicative guideline, a CAC that represents between 15% and 25% of the average net margin per vehicle is reasonable. Above 30%, the channel starts consuming too much profitability.
How long does it take to see a positive ROI on Meta Ads campaigns?
Meta campaigns have a learning period of up to 7 days. To have representative data on conversion, you need at least 3 or 4 weeks and a minimum of 20 or 30 leads. Judging the ROI of a campaign with less data than that leads to incorrect decisions.
Does it make sense to calculate the ROI of car portals if I already pay a flat monthly fee?
Yes. Even if the cost is fixed, performance varies depending on the month, season, and type of stock you have published. Calculating how many sales you attribute to each portal each month and dividing the monthly cost by that number gives you the actual CAC of that channel, which can vary significantly from one month to another.
How do I attribute a sale if the buyer contacted me through several different channels?
The standard practice in the sector is attribution to the last channel before purchase, although it is not perfect. A more precise alternative is to ask the buyer directly how they found out about the dealership or the specific car. This question, incorporated into the closing process, provides more reliable data than any automatic tracking system.
