10 min read The Metrics you NEED to Track in Performance Marketing

Scaling your digital or eCommerce business starts with focusing on the metrics that actually matter. Forget vanity metrics like traffic, impressions, or engagement – what matters are the numbers that directly impact your bottom line.

If you’re not calculating these properly, you’re guessing. And guessing won’t help you grow. These metrics will show you where your business is making money, where it’s leaking cash, and where to optimise for real impact.

We’ll break them down step-by-step in order, starting with revenue. Each calculation builds on the one before it, and without getting the basics right, the rest won’t add up.

Using a 12-month example, I’ll show you how these metrics connect to give you actionable insights into your business. Get these right, and you’ll have a roadmap for scaling smarter, not harder.

*Disclaimer: All numbers used in the examples provided are for illustrative purposes only and do not reflect actual business data. These figures are entirely fictional and are intended solely to demonstrate how to calculate and interpret key metrics.

In this example, the business generates £1,000,000 in annual revenue by selling 20,000 units at a price of £50 per unit.

This is your starting point. There’s no business without solid revenue, but it’s just the top-line number.

But in eCommerce, revenue can come from multiple streams. Think subscription models, upsells, cross-sells, affiliate partnerships, or even ad revenue. It’s rarely as simple as one calculation. That’s why recording all your revenue and understanding how it’s attributed is critical. You need a clear picture of what’s driving growth and where.

First-party data is the key here. By tracking customer purchase history, LTV, and retention data directly, you avoid relying on inaccurate third-party data. This level of detail helps you pinpoint which products, campaigns, or channels which making money – and where to double down. Without it, you’re risking blind spots in your strategy.

The Gross Profit Margin is 60%, which means the company is left with 60% of its revenue after covering direct production costs.

In general, a gross profit margin between 50% and 70% is strong for most eCommerce businesses. It gives you enough room to cover other operating costs like marketing, salaries, and overheads while still being profitable.

However, it depends on your business model, for example DTC eCommerce or luxury goods can see higher gross profit margins due to price point and cutting out middlemen and distributors who typically operate on a % of sale model.

According to Shopify, a good CVR for an eCommerce store generally falls in the 2.5% to 3% range. So, with a CVR of 1.4%, there’s some work to be done here.

To improve this, you can focus on increasing the sales volume per visitor or optimising the quality of traffic coming to your website.

This CVR would suggest to me that ROAS needs optimising or audience targeting / creative assets need to be re-worked to re-engage… but more on those in a minute.

If 15% of your customers are repeat buyers then your Retention Rate is 15%. But to really scale, you’ll want to push that retention rate higher. This is because not retaining your existing customers and consistently chasing new ones can cost up to 5 times more…. ouch. Chasing customer acquisition will drastically decrease your CAC (more on this soon).

On the face of it a 2.0 ROAS is not ground breaking. Particularly with the COGS & Ad-spend, we’re now at £700,000 costs in the P&L before operating costs and people…

A “good” ROAS for eCommerce is between a 3:1 or 4:1 ROAS, however at Onelink we have consistently exceeded this by having excellent platform management across paid search, paid social and programmatic with excellent ad creative to get the most out of ad platforms.

If you’re operating at anything less than a 4:1 ROMs, I’d recommend reconsidering your marketing strategy and tactics. Unless you’re a start-up with funding, willing to burn through capital for long-term growth, you should have a clear plan to ramp up your ROI quickly. Operating with a lower ROMs can severely impact your cash flow and limit your ability to scale efficiently.

For established businesses, consistently hitting lower ROMs means you’re likely wasting ad spend or not converting the right traffic, or spending too much on agency fees or marketing activity which is not driving sales. That’s not sustainable. Every marketing campaign should be analysed and optimised to ensure it’s driving profitable growth, not just top-line revenue.

If you can’t hit that 4:1 ROMs threshold, it’s time for a deep audit of your channels. Tweak your strategies, and focus on the metrics that actually matter – like conversion rates, retention, and customer lifetime value.

Don’t just throw money at ads hoping something sticks. Get strategic, understand the numbers, and course-correct fast. The sooner you adjust, the quicker you’ll get back to profitable growth.

A good Customer Acquisition Cost (CAC) for eCommerce typically ranges between 20-30% of your average customer’s first purchase value, according to benchmarks shared by Shopify and other industry leaders. This ensures your business is balancing acquisition costs with profitability. However, CAC should ideally decrease over time as repeat purchases and customer lifetime value (LTV) grow.

Disclaimer: The ideal CAC can vary greatly depending on your industry, product margins, customer lifetime value, and marketing strategy. Use this as a guideline, but always compare your CAC against your LTV and gross profit margins to determine sustainability for your specific business.

In this example the CAC for this fictional business is far too high!

Disclaimer: All the numbers in this article are fictional and intended for educational purposes only.

That said… this scenario isn’t far from reality for many growing brands navigating digital and performance marketing. And let’s be honest – bad agencies are often the biggest culprits, focusing on vanity metrics like impressions, clicks, and traffic. Sure, those numbers might look good in a report, but they’re meaningless if the traffic isn’t converting at a sustainable rate.

In the example we walked through, it’s easy to see how vanity metrics can paint a misleading picture. A business with over £1M in annual turnover, a solid 60% gross profit margin, and a strong AOV can still find itself in serious financial trouble if backend economics aren’t tracked properly. In this case, the business racked up £938,000 in costs before overheads – leaving it in the red.

This highlights why understanding the metrics that matter – like conversion rates, ROAS, and retention rate – is critical. It is non-negotiable to know where your ad spend is going and whether it’s driving actual performance.

Tactics to Avoid Burning Cash in Digital

So, how do you make sure this doesn’t happen? Here are some actionable tactics every brand should follow:

1. Track Full-Funnel Metrics

Don’t stop at impressions, clicks, or traffic. These metrics might look good on paper, but they don’t tell you if your marketing is actually driving sales or profitability. You need to connect those numbers to real business outcomes.

For example, impressions show how many people see your ad, but if they’re not converting, it’s wasted effort. Clicks might get people to your site, but if they don’t complete a purchase, those clicks don’t matter.

Focus on metrics like conversion rate (CVR), customer acquisition cost (CAC), and return on ad spend (ROAS) to track how well your traffic is turning into revenue.

The real goal is to understand how all these efforts impact your bottom line—are your ads bringing in customers who stick around and buy again? Tracking the right metrics ensures you’re investing in strategies that actually grow your business.

2. Calculate Metrics Regularly

• Measure metrics like CAC, LTV, and ROAS monthly (at a minimum). These numbers change as campaigns scale, and even small inefficiencies can add up fast.
• Factor in every cost: agency fees, creative production, salaries, shipping, and any other expense tied to marketing. Half the battle is understanding your true costs.

3. Use Customer Segmentation

Understand the lifetime value and retention rate of different customer segments. Returning customers often drive more profit, so allocate budget and resources toward retention strategies like email campaigns, loyalty programs, and upsell opportunities.

4. Focus on CRO (Conversion Rate Optimisation)

Audit your website for speed, UX, and checkout flow. Improving conversion rates even by 0.5% can drastically reduce your CAC.

5. Prioritise Retention Over Acquisition

Retaining customers is cheaper and often more profitable than acquiring new ones. Focus on building a strong retention strategy – personalised email flows, regular follow-ups, and post-purchase surveys to stay connected with customers.

6. Set Realistic Targets and Benchmarks

Define your targets for metrics like ROMs and ROAS before campaigns even launch. For example, if your goal is a 4:1 ROMs, every campaign should be evaluated against that benchmark to ensure long-term profitability.

7. Run Financial Projections

Before scaling campaigns, map out how the added spend will impact your entire P&L. A £50k increase in ad spend might boost revenue, but if your gross profit margin or retention isn’t strong enough, it could leave you in a worse position financially.

Onelink’s Approach to Measuring and Managing Metrics

At Onelink, we take the guesswork out of performance marketing by focusing only on the metrics that drive actual business growth. Our approach is rigorous, data-driven, and results-focused:

1. End-to-End Tracking

We don’t just stop at ROAS or top-line revenue. We measure the full customer journey—from acquisition to retention—and connect the dots back to profitability. Every metric we track is tied to real, tangible results.

2. Custom Reporting

We create tailored dashboards for each client, showing key metrics like ROMs, CAC, CVR, and LTV in one place. This transparency ensures our clients know exactly where their money is going and how it’s performing. It can be scary sharing your cold hard numbers with an agency, but we’re here to help you grow not get an influx of traffic from a campaign. Be transparent with us on everything you can be, it will pay dividends.

3. Retention-First Strategies

Many agencies focus purely on acquisition, but at Onelink, we make retention a core part of every strategy. This includes supporting retention-focused email flows, loyalty programs, and personalised ad campaigns to maximise lifetime value.

4. Granular Optimisation

We don’t just optimise campaigns based on cost per click or impressions. Our team analyses every layer – creative performance, audience targeting, bidding strategies, and placement – to ensure we’re driving sales that make sense with the back-end metrics so you’re growing sustainably.

5. Real-Time Monitoring

Marketing isn’t static, and neither are the numbers. Our team continuously monitors performance, adjusts spend, and refines strategies to meet evolving KPIs. This agility ensures no money is wasted.

6. Education and Partnership

We don’t just run campaigns—we educate our clients on how to understand the numbers. This partnership approach ensures they’re always in control of their marketing performance and can make informed decisions for growth.