SurrfomanceThe cost of the wrong number
Every campaign optimises toward something. If nobody chose deliberately, the platform chose for you — usually clicks or conversions defined loosely enough to include newsletter signups.
The visible result is a report that improves while the business doesn't. Impressions up, clicks up, cost per click down, and the same number of new customers as last quarter.
Match the KPI to the business model
Lead-generation businesses
Clinics, law firms, brokerages, home services. Revenue happens on a call or in an appointment, not on the website.
Optimise for: cost per qualified lead, then cost per booked appointment once your CRM can feed that back. Ignore: ROAS, which has no meaningful value at conversion time.
E-commerce and D2C
Transaction value is known immediately, which makes measurement easier and complacency more likely.
Optimise for: contribution margin after cost of goods and shipping, not headline ROAS. A 4x ROAS on a product with 20% margin loses money. Watch: new-customer versus returning-customer split, so you know whether you're growing or remarketing to the same people.
CPG and retail
The purchase often happens offline, on a shelf, weeks after the exposure. Last-click attribution is structurally incapable of measuring it.
Optimise for: reach against your target demographic, frequency, and repeat purchase rate where you have it. Accept: that some of the value will not be directly attributable, and use holdout tests or regional comparisons instead.
Apps and subscriptions
Optimise for: cost per activated user rather than cost per install, and retention at day 7 and day 30. An install that never opens the app twice is a cost, not a customer.
One primary, two supporting
Pick one KPI that decisions are judged against, and no more than two supporting metrics that explain movement in it. A clinic might use cost per booked appointment as primary, with lead volume and appointment show rate as supporting. That is enough to diagnose a problem without drowning in a dashboard.
Agree it before anything is built
The KPI conversation has to happen before the site is designed and before the first campaign goes live, because it determines what gets tracked, how pages are structured, and what counts as a conversion. Retrofitting measurement onto a live campaign means the first months of data are unusable.
Frequently asked questions
What is the most important marketing KPI?
There is no universal answer. Lead-generation businesses should optimise for cost per qualified lead or booked appointment. E-commerce businesses for return on ad spend and contribution margin. CPG and retail brands for reach, frequency and repeat purchase rate.
What is the difference between a metric and a KPI?
A metric is anything measurable. A KPI is the specific metric your business decisions are judged against. Clicks are a metric. Cost per booked appointment is a KPI.
Why is ROAS a bad KPI for service businesses?
Return on ad spend requires a transaction value at the point of conversion. Service businesses convert to an enquiry, with revenue realised later and variably, so ROAS misrepresents performance.