The four metrics every growth team should put on the wall
nCAC, payback, blended MER and creative half-life. Why these four, and the dashboards we build around them.
Most growth dashboards we inherit have somewhere between fifteen and forty metrics on them, and the teams running those dashboards can usually tell you, when pressed, that they mainly look at three or four of them and the rest are noise carried over from whichever platform's default report someone screenshotted eighteen months ago. We've settled on four numbers that we put in front of every client, and we've deliberately left everything else off the wall.
nCAC — customer acquisition cost, adjusted for who actually converts
Blended CAC — total spend divided by total customers — is the number most teams default to, and it's misleading because it treats every acquired customer as equally valuable. nCAC adjusts for that by weighting acquisition cost against the customer segments that actually retain and pay, so it doesn't reward a channel for cheaply acquiring customers who churn in week one. It's a harder number to compute and a much more honest one to optimise toward.
Payback period — the number that decides how fast you can actually spend
How many months of revenue from a customer does it take to recover what you spent acquiring them? This is the number that actually gates growth-spend velocity, more than any efficiency metric — a business with a 3-month payback can reinvest and compound far faster than one with a 14-month payback, even at identical CAC, because the cash comes back around fast enough to fund the next round of spend.
Blended MER — the sanity check that catches platform-reported lies
Marketing efficiency ratio, calculated as total revenue over total marketing spend across every channel combined, is the number that can't be gamed by any single platform's attribution window, because it doesn't rely on attribution at all — it's just top-line revenue against total spend. When individual platforms all report healthy in-platform ROAS but blended MER is quietly declining, that's the earliest and most reliable signal that attribution is double-counting somewhere and the individual numbers can't be trusted at face value.
Creative half-life — the leading indicator nobody tracks
How long does a given creative asset hold efficient CPMs before fatigue sets in and cost climbs? Most teams only notice creative fatigue after CPMs have already risen and margin has already been lost — half-life turns that into a leading indicator, letting a team ship the next variant before performance actually degrades rather than reacting once it has. It's the only one of the four that's about production planning rather than financial reporting, and it's usually the one most neglected.
Why these four and not fifteen
Each of these four numbers answers a different question a growth operator actually has to answer weekly: what does a customer cost, how fast do I get that back, is the whole system actually working net of platform noise, and when do I need fresh creative. Everything else on a typical dashboard is either a component that rolls up into one of these four, or a vanity number that platforms surface because it flatters them, not because it should drive a decision. Four numbers you actually look at every week beat forty you screenshot and ignore.
