Cohorts and lifetime value answer the question that sets your entire acquisition budget: what is a customer worth over time. This guide is for whoever decides what you can afford to pay to acquire one. It covers how to read a cohort table, what the lifetime value curve is telling you, and why net revenue retention is the number to watch above all the others.
How a cohort table works
A cohort is a group of customers who first bought in the same month. The table follows each group forwards, showing what proportion came back in month one, month two and so on.
Reading it down a column tells you how a particular month of customers behaved over time. Reading it across a row compares different acquisition months at the same age, which is the comparison that matters. Customers acquired in November have had longer to come back than customers acquired in March, so comparing their totals is meaningless. Comparing both at month three is not.
The most useful thing a cohort table reveals is whether your acquisition is getting better or worse. If recent cohorts return at a lower rate than older ones at the same age, you are buying worse customers, even while your headline revenue grows. That is the failure mode that looks like success for two quarters and then stops.
The lifetime value curve
The curve shows cumulative revenue per customer as their relationship ages. It rises steeply at first, then flattens.
Where it flattens is the practical question. A curve that reaches most of its value in the first sixty days means you recover acquisition cost quickly and can afford to spend aggressively. A curve that keeps climbing for a year means your customers are more valuable than your first order suggests, but you need the working capital to wait for it.
Do not read the far end of the curve too confidently. The oldest cohorts are the only ones that have reached it, and they are usually your earliest customers, who found you differently and often behave better than the people you acquire at scale today.
Net revenue retention is the number
Net revenue retention compares what a cohort is worth now against what the same cohort was worth when it started. It captures repeat purchases, larger orders and churn in a single figure.
Above one hundred per cent means your existing customers are collectively growing in value without you acquiring anyone new. That is the strongest position a business can be in, and it is invisible if you only watch new customer counts.
Below one hundred per cent is normal for most ecommerce brands and is not a crisis. It means growth has to come from acquisition, which is fine as long as you know that is the machine you are running and have priced acquisition accordingly.
What this sets
Your maximum acquisition cost follows from the curve rather than from the first order. If a customer is worth a certain amount by month six and you can fund the gap in between, you can pay more than a single order’s margin to acquire them.
That is the calculation most brands do informally and get wrong in one of two directions. Paying only what the first order supports leaves growth on the table. Paying what the twelve month value supports without the working capital to bridge it is how profitable businesses run out of cash.
What to check first
Look at whether recent cohorts are tracking with older ones at the same age. If they are, your acquisition quality is holding and you can scale. If they are falling, more spend will make the problem larger rather than the revenue larger, and the answer is in what changed about the channel mix or the offer rather than in the budget.