If the answer to "are the ads working?" is "yes, lots of likes", there is no measurement system. Likes, impressions and clicks are useful metrics, but the business owner's question is different: how many customers and how much revenue did this spend bring?
A KPI (Key Performance Indicator) is one of a small number of indicators that answer this question. In this guide we cover the difference between a KPI and a metric, the most common marketing indicators with formulas, how to track them in GA4 and a CRM, and how to build a monthly report.
Short answer: a marketing KPI is a measurable indicator tied directly to a business goal — for example, customer acquisition cost (CAC), return on ad spend (ROAS) or the number of qualified leads. Two to four KPIs per channel are enough.
KPI vs metric: what is the difference
Every KPI is a metric, but not every metric is a KPI. A metric is any number you measure: sessions, CTR, likes. A KPI is a selected metric that shows whether you are reaching a business goal and drives decisions.
| Goal | KPI | Supporting metrics |
|---|---|---|
| More enquiries | Qualified leads, CPL | Clicks, CTR, form conversion rate |
| Grow online sales | Revenue, ROAS, CAC | Add to basket, checkout starts |
| Brand awareness | Growth in branded searches, reach | Impressions, video views |
| Retain customers | Repeat purchase rate, CLV | Email opens, active users |
The SMART rule
A good KPI target is specific, measurable, achievable, relevant and time-bound. "Grow sales" is not a target; "grow orders from organic search this quarter versus last quarter, tracked monthly" is.
Key marketing metrics and formulas
| Metric | Formula | What it shows |
|---|---|---|
| Conversion rate (CR) | Conversions ÷ sessions (or clicks) × 100 | How much traffic takes action |
| CPL — cost per lead | Ad spend ÷ leads | The price of one enquiry |
| CPA — cost per action | Spend ÷ conversions | The price of one sale or sign-up |
| ROAS | Revenue from ads ÷ ad spend | How much revenue each 1 AZN of ads brings |
| CAC — customer acquisition cost | Total marketing and sales cost ÷ new customers | The real price of a new customer |
| CLV — customer lifetime value | Average order value × purchase frequency × relationship length | Revenue a customer brings over the whole period |
| MER | Total revenue ÷ total marketing spend | Efficiency of all channels combined |
A worked example
Say 1,000 AZN a month is spent on ads, 40 leads arrive and 8 of them become customers. Then CPL = 1,000 ÷ 40 = 25 AZN, and CAC (excluding sales team costs) = 1,000 ÷ 8 = 125 AZN. If an average customer's CLV is 400 AZN, the channel is profitable; if it is 100 AZN, every new customer is a loss.
Even with a high ROAS, a campaign can lose money if the product margin is low. Always assess KPIs together with margin and CLV.
Choosing KPIs by channel
SEO
- Conversions from organic search (the main KPI).
- Clicks and impressions from non-branded queries in Search Console.
- Index status of key pages.
Google Ads
- CPA or ROAS (depending on the campaign goal).
- Conversion rate and impression share.
- Quality Score as a supporting metric — see our Quality Score article.
Meta Ads
- Cost per lead or per purchase.
- CTR and conversions per creative — for testing see our creative testing article.
- Frequency — a signal of ad fatigue.
Content and SMM
- Conversion paths that start with content.
- Saves and shares — more meaningful than likes, which are a vanity metric.
- Growth in branded searches.
How to track KPIs in GA4
GA4 is an event-based model: page views, form submissions, purchases — all are events. Events that matter to the business are marked as key events; in 2024 Google replaced the term "conversions" with "key events" in GA4.
The minimum setup
- Set up generate_lead for a lead business or purchase for e-commerce, and mark it as a key event.
- Track form, call and WhatsApp clicks as separate events through Google Tag Manager.
- Use UTM parameters on every ad link (utm_source, utm_medium, utm_campaign).
- Link your Google Ads account to GA4 and import conversions.
- See traffic from AI assistants in a separate channel group — we show how in our AEO/GEO guide.
Attribution
Several channels can contribute to one sale: the user first sees an Instagram ad, then searches on Google and buys. GA4's data-driven model distributes the credit across channels. We explain how we present this to clients in our attribution article.
CRM: from lead to sale
GA4 sees what happens on the site, but not what happens after the enquiry: did the lead become a sale or not? That is where a CRM (Customer Relationship Management) comes in. This was also the most practical part of the CRM post on our old blog.
- Store each lead's source (UTM or channel) in the CRM.
- Define lead stages: new, contacted, proposal sent, won, lost.
- Once a month, calculate the "lead → sale" rate per channel.
- Where possible, send sales results back to ad platforms (offline conversion import) so the algorithm optimises for quality leads.
HubSpot, Bitrix24, Zoho or even a well-built spreadsheet can be a start for a small business. More important than the tool is recording each lead's source and outcome.
A monthly KPI report: a template
A report is not a list of numbers but a decision document. A one-page structure:
- Summary (3 sentences): what went well, what went badly, what we do next month.
- Key KPIs: this month, last month, target — as a table.
- By channel: spend, conversions, CPA/ROAS.
- Reasons: explanation of changes (seasonality, new creative, price change).
- Next steps: 3–5 concrete actions.
Tools like Windsor.ai or Looker Studio save time by combining GA4, Google Ads and Meta data in one report. But an automated dashboard is incomplete without commentary: a person has to explain why a number changed.
Frequently asked questions
What is a KPI?
A KPI (Key Performance Indicator) is a key measurable indicator showing whether you are reaching a business goal — for example, customer acquisition cost or revenue from ads.
What is the difference between a KPI and a metric?
A metric is any measured number (clicks, likes, sessions). A KPI is a selected metric tied directly to a business goal and used for decisions.
How many KPIs should I track?
Two to four per channel are enough. Too many indicators scatter attention; supporting metrics are tracked separately to understand causes.
What is the difference between ROAS and CAC?
ROAS is revenue from ads divided by ad spend. CAC is the total cost of acquiring one new customer and usually includes sales costs too.
What is a key event in GA4?
An event that matters to the business and is marked separately — for example, a form submission or a purchase. In 2024 Google replaced the term "conversions" with "key events" in GA4.
Can I track KPIs without a CRM?
You can track on-site metrics with GA4, but to see whether a lead became a sale you need a CRM, or at least a system that records each lead's source and outcome.
Conclusion
A good measurement system is a small number of well-chosen KPIs, a properly configured GA4 and a CRM that follows what happens to each lead. Without these three, marketing decisions rest on opinion; with them, on data.
If you want to learn GA4 and GTM in practice, we run a Web analytics course. For the overall map of channels, see our digital marketing guide.
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