Solved: Struggling with Paid Ads ROI Calculation in Paris

Hi there,

Thanks for reaching out!

I had a read through your problem, and it's a common one, especially in a hyper-competitive market like Paris. It's easy to burn through cash and have no real idea if it's actually moving the needle. The good news is that the feeling of uncertainty you have isn't down to a flaw in your maths, but more likely a flaw in the metric everyone tells you to track.

So, I've put together some of my thoughts for you. The aim here isn't just to help you calculate ROI better, but to give you a completely different—and frankly, more profitable—framework for thinking about your entire paid advertising strategy. Forget about tweaking bids for a moment; we need to fix the foundations first.

You're asking the wrong question...

Right, let's get straight to it. The reason you're struggling to get a clear picture of your ROI is because you're probably focused on Return on Ad Spend (ROAS). Everyone is. It's simple, it's immediate, and it feels like you're measuring something useful. It's also one of the most misleading metrics in marketing.

ROAS tells you what you got back *today* from what you spent *today*. For an e-commerce store selling cheap impulse-buy products, maybe that's fine. But for any business with a considered purchase, a longer sales cycle, or repeat custom, it's like judging a marathon runner based on their first 100-metre split. It's a snapshot that tells you almost nothing about whether you'll actually win the race.

In a market like Paris, competition drives up click costs. If you're judging success on immediate ROAS, you'll always feel like you're losing. You'll switch off campaigns that are actually bringing in your most valuable long-term customers because they didn't buy within the arbitrary 7-day attribution window. It's a recipe for short-term thinking and stalled growth. The real question isn't "What's my ROAS?" The real question is, "How much can I afford to spend to acquire a customer that will make me profitable over their entire lifetime?" Answering that changes everything.

Let's talk about the only metric that really matters: LTV to CAC

To run paid advertising profitably and with confidence, you need to operate on two core metrics: Customer Lifetime Value (LTV) and Customer Acquisition Cost (CAC). The ratio between them is the true health-check of your marketing.

LTV is the total profit you'll make from an average customer over the entire period they do business with you.

CAC is the total amount you spent on sales and marketing to acquire that one customer.

A healthy, sustainable business typically has an LTV to CAC ratio of 3:1 or higher. This means for every £1 you spend to get a customer, you get £3 back in profit over their lifetime. A 1:1 ratio means you're losing money once you factor in overheads. A 5:1+ ratio is fantastic and means you should be pouring more fuel on the fire.

When you know these numbers, you stop worrying about daily CPC fluctuations. You start making strategic decisions. A £250 lead from LinkedIn might seem expensive on the surface, but if you know your LTV is £10,000 and that 1 in 10 of those leads becomes a customer, you're essentially paying £2,500 to make £10,000. That's not an expense; it's an investment with a 4x return. Now you can see why this is so much more powerful than ROAS.

I'd say you need to calculate your Customer Lifetime Value (LTV) first...

This is the starting point. If you don't know what a customer is worth, you have no idea what you can spend to get one. The calculation is more straightforward than you might think. You just need three pieces of data from your business.

1. Average Revenue Per Account (ARPA): What's the average amount a customer pays you per month (or per year, just be consistent)?

2. Gross Margin %: What's your profit margin on that revenue? Don't use 100% of the revenue; you need to account for your cost of goods sold (COGS) or the direct costs of servicing that client.

3. Monthly Churn Rate %: What percentage of your customers do you lose each month? This is critical. A lower churn means a higher LTV.

The formula is:

LTV = (ARPA * Gross Margin %) / Monthly Churn Rate

Let's run a quick example. Say you run a SaaS business:

• ARPA = £200/month
• Gross Margin = 80% (0.8)
• Monthly Churn = 5% (0.05)

LTV = (£200 * 0.80) / 0.05

LTV = £160 / 0.05 = £3,200

So, each new customer is worth £3,200 in gross margin to your business over their lifetime. This number is your new North Star. It's the foundation for your entire budget.

To make this easier, I've built a simple calculator for you. Play around with the numbers to see how small changes in churn or margin can drastically affect your LTV.

You probably should figure out your Target Acquisition Cost...

Once you have your LTV, you can work backwards to figure out what you can afford to spend. This simple bit of maths removes all the guesswork from your ad spend.

Let's stick with our LTV of £3,200 from the earlier example. And let's say we're aiming for that healthy 3:1 LTV:CAC ratio.

Target CAC = LTV / 3

Target CAC = £3,200 / 3 = ~£1,066

This means you can afford to spend up to £1,066 on sales and marketing to acquire a new customer and still run a very profitable operation. This is your budget. This is your permission to spend.

But we can go deeper. Most advertising campaigns don't acquire customers directly; they generate leads, trials, or consultations first. So you need to know your target Cost Per Lead (CPL). For that, you need to know your lead-to-customer conversion rate.

Let's say your sales team, or your onboarding process, converts 1 in 10 qualified leads into a paying customer (a 10% conversion rate).

Target CPL = Target CAC * Lead-to-Customer Conversion Rate

Target CPL = £1,066 * 0.10 = £106.60

And there you have it. You can now confidently run ad campaigns aiming for a CPL of up to £106. Suddenly, a £50 CPL from Google Ads isn't "expensive"—it's a bargain. You're paying £50 for a lead that, on average, will lead to a £1,066 customer. You're printing money. This is how you scale aggressively and intelligently, even in a competitive market.

We'll need to look at your customer targeting...

Now that we know our numbers, we need to find the right people. This is where most businesses go disastrously wrong. They define their Ideal Customer Profile (ICP) with sterile demographics. "Companies in the finance sector in Paris with 50-200 employees." This tells you precisely nothing of value and leads to generic, ineffective ads.

You need to stop thinking about demographics and start thinking about nightmares.

Your real ICP is defined by a specific, urgent, expensive, and possibly career-threatening problem. Your customer isn't a job title; they're a person lying awake at 3 AM terrified of something. Your job is to find that 'something'.

• For a cybersecurity firm, the nightmare isn't 'needing better security'; it's the CTO terrified of being the next headline for a data breach.
• For a fractional CFO service, the nightmare isn't 'needing financial advice'; it's the founder one bad month away from a payroll crisis.
• For an e-commerce brand selling high-quality baby products, the nightmare isn't 'needing a pram'; it's the expecting mother overwhelmed by choice and terrified of buying something unsafe for her newborn.

Once you isolate that nightmare, your entire strategy changes. You stop targeting "CFOs" and start targeting the problem state. How do you find them? You find their watering holes. Where do people with this specific nightmare go for information and relief?

• -> What niche podcasts do they listen to on their commute? (e.g., 'Acquired' for tech leaders)
• -> What industry newsletters do they actually open and read? (e.g., 'Stratechery' for strategy professionals)
• -> What software tools do they already pay for? (e.g., HubSpot, Salesforce, Xero)
• -> What specific influencers or thought leaders do they follow on LinkedIn or Twitter? (e.g., Jason Lemkin for SaaS founders)
• -> What private communities or Facebook Groups are they members of?

This intelligence is the blueprint for your targeting. On LinkedIn, you can target members of specific groups. On Meta, you can target followers of specific pages or people with interests in specific software. This is how you get your message in front of a pre-qualified audience instead of just shouting into the void. This work is not optional. Do it first, or you have no business spending a single euro on ads.

You'll need a message they can't ignore...

Once you know who you're talking to and what keeps them up at night, crafting compelling ad copy becomes much easier. You're not selling features; you're selling the solution to their nightmare. Here are a couple of tried-and-tested frameworks we use.

For a B2B Service (Problem-Agitate-Solve):

• Problem: State their nightmare directly. "Are your cash flow projections just a shot in the dark?"
• Agitate: Pour salt on the wound. Make them feel the pain. "Are you one bad month away from a payroll crisis while your competitors are confidently raising their next round?"
• Solve: Introduce your service as the clear, simple solution. "Get expert financial strategy for a fraction of a full-time hire. We build dashboards that turn uncertainty into predictable growth."

For a B2B SaaS Product (Before-After-Bridge):

• Before: Paint a picture of their current hell. "Your AWS bill just arrived. It’s 30% higher than last month, and your engineers have no idea why. Another fire to put out."
• After: Show them the promised land. "Imagine opening your cloud bill and smiling. You see where every dollar is going and waste is automatically eliminated."
• Bridge: Position your product as the vehicle to get them there. "Our platform is the bridge that gets you from chaos to control. Start a free trial and find your first €1,000 in savings today."

The key here is emotion. B2B purchases aren't purely logical. They are made by people who want to avoid pain, look good to their boss, and reduce their personal stress. Speak directly to those motivations.

I'd say you should delete the "Request a Demo" button...

This might be the most important—and controversial—piece of advice I can give you. The most common point of failure for B2B advertising is the offer. And the "Request a Demo" button is possibly the most arrogant, high-friction Call to Action ever invented.

It presumes your prospect, a busy decision-maker, has nothing better to do than book a 30-minute slot in their diary to be sold to. It offers them zero immediate value and positions you as just another commodity vendor. It's a conversion killer.

Your offer's only job is to deliver an "aha!" moment of undeniable value that makes the prospect sell themselves on your solution. You must solve a small, real problem for free to earn the right to solve their whole problem for a price.

• If you're a SaaS company: The gold standard is a free trial or a freemium plan. No credit card. Let them use the actual product and feel the transformation. A user who sees the value firsthand is a Product Qualified Lead (PQL), which is infinitely more valuable than a Marketing Qualified Lead (MQL) from a form fill. We worked with a B2B software client and helped them get 4,622 registrations at a cost of $2.38 per registration.
• If you're a service business: You need to bottle your expertise into a tool or asset. For a marketing agency, it could be a free, automated SEO audit. For a data analytics firm, a 'Data Health Check' that flags issues in their database. For us, it's a 20-minute strategy session where we audit failing ad accounts for free. It gives the prospect immense value and proves our expertise without any hard selling.

Rethink your offer. Lower the friction, increase the immediate value, and watch your conversion rates—and your ultimate ROI—climb.

This is the main advice I have for you:

To pull this all together, here is a summary of the actionable steps I'd recommend. This is the framework for moving away from guesswork and towards a predictable, scalable advertising machine.

Following this process isn't easy, and it requires a shift in mindset from short-term tactics to long-term strategy. It means doing some upfront work on your numbers and customer research before you even think about writing an ad. But this is what separates the businesses that struggle with ROI from those that build predictable growth engines.

It can be a lot to take on, especially when you're busy running your business. This kind of deep strategic work is exactly what we specialise in. We help businesses implement this framework to get clarity on their numbers and build profitable, scalable paid advertising campaigns. Getting an expert eye on this, particularly in a tough market, can make a huge difference and save you a lot of wasted time and money.

If you'd like to chat through your specific situation in more detail, we offer a free, no-obligation initial consultation where we can review your current strategy and provide some more tailored advice. It's often the quickest way to identify the biggest opportunities for improvement.

Hope this helps!

Regards,

Team @ Lukas Holschuh