Ecommerce Unit Economics: Can Your Store Afford to Grow?

Ecommerce unit economics answer one question: does each new customer make you money, and how fast? You compare what a customer contributes in margin, across their first order and every order after it, against what you paid to acquire them. If the margin covers the cost inside your cash cycle, the store can afford to grow. If it doesn't, more spend makes the problem bigger.

Most stores look at revenue and return on ad spend instead. Both can look healthy while every new customer loses money. Unit economics strip that away.

What are unit economics in ecommerce?

Unit economics measure the profit or loss of one unit of the business. In ecommerce, the unit is usually an order or a customer. Each view answers a different question. To run your own numbers, use our break-even ROAS calculator.

Per order: does selling this order make money after its variable costs? That's contribution margin per order. Our guide to contribution margin in ecommerce covers the calculation in full.

Per customer: does acquiring this customer make money over the time they stay with you? That's contribution over the customer's life, compared with acquisition cost.

The per-customer view is the one that decides growth. A store can lose money on every first order and still be very healthy, if customers come back. A store can make money on every first order and still be stuck, if nobody returns and acquisition costs are rising.

Which numbers make up ecommerce unit economics?

Four inputs. Everything else is a combination of them.

From these, you get the two numbers that matter: contribution per customer over a set period and payback period, the time until that contribution covers acquisition cost.

How do you calculate ecommerce unit economics? A worked example

Here's an example with round, hypothetical numbers, not data from any store. Picture a brand selling a consumable product.

• First order: $60 revenue, $26 contribution before marketing
• Customer acquisition cost: $40
• Repeat orders: $60 revenue, $28 contribution (slightly higher, because returning buyers use fewer discounts)
• Expected repeat orders in the first 12 months: 0.8 per customer, on average

First order: $26 contribution − $40 acquisition cost = −$14. Every new customer starts $14 in the hole.

First 12 months: $26 + (0.8 × $28) = $48.40 contribution per customer. Minus $40 acquisition cost = $8.40 per customer after a year.

So the store makes money on customers, but slowly. If most repeat orders arrive in months four to nine, payback lands somewhere in that window. Every new customer is a loan the store makes to itself for most of a year.

Can your store afford to grow?

That's the real question, and the example shows why it's not the same as "is the store profitable?"

The brand above is profitable per customer. But to grow, it has to fund $14 per new customer upfront and wait months to earn it back. Double the new customers, and you double the cash tied up. A store in that position can be profitable on paper and run out of cash while growing.

Three tests decide whether growth is affordable:

1. Does contribution per customer exceed acquisition cost? If not, growth loses money. Stop and fix the economics.
2. Does payback fit inside your cash cycle? If you pay suppliers and ad platforms well before customers pay you back, growth needs financing. Know how much.
3. Does acquisition cost hold as you spend more? Average acquisition cost usually rises as you scale, because the easiest buyers are reached first. The last dollar of spend buys the most expensive customer.

The third test catches a lot of stores out. Your unit economics at today's spend aren't your unit economics at double the spend. Model the marginal customer, not the average one.

Which levers improve unit economics?

Each lever moves one of the four inputs. Here's what each does to the example above, again with hypothetical numbers.

Two things stand out.

First-order contribution matters as much as acquisition cost. Most stores pour effort into lowering acquisition cost through ad optimisation, a lever they share with every competitor bidding on the same audience. Raising first-order contribution through price and order value is often more within your control.

Mountain Ice is the real-world version: an average order value below $20 left almost no margin to bid against on paid traffic and capped what it could spend per customer. Moving it to $39 raised first-order contribution and the room to scale.

The levers compound. Each improvement is modest on its own. Together, the per-customer result more than triples and the first order nearly breaks even. That compounding is why the order of work matters.

Raising first-order contribution

The first order has to carry the acquisition cost, so it's where unit economics are won or lost. Price, order value, discount discipline and shipping rules all sit here. We cover pricing in ecommerce pricing strategy.

Raising repeat orders

Repeat orders are cheap contribution, because you've already paid to acquire the buyer. Even a small rise in repeat behaviour changes the per-customer math. Our post on repeat purchase rate covers what moves it, and customer lifetime value in ecommerce covers how to raise the total a customer is worth.

We once argued a client should show the one-time purchase option next to the subscription. The client stayed subscription-first because its own retention data supported it. Measured repeat behaviour beats assumptions, including ours.

What about the lifetime value to acquisition cost ratio?

You'll often see unit economics summarised as a ratio of lifetime value to acquisition cost. It's a convenient shorthand, but it hides the thing that most often breaks growing stores: time.

Two stores can share the same ratio. One earns back its acquisition cost on the first order. The other takes two years. The first can grow as fast as it finds buyers. The second needs a lot of cash to grow at all. The ratio treats them as identical.

There's also the question of how lifetime value is measured. A ratio built on revenue rather than contribution margin looks far healthier than the business is. If you use a ratio, build it on contribution and pair it with payback period.

What mistakes distort unit economics?

These are the ones we look for first.

• Measuring lifetime value on revenue. It inflates what customers are worth and justifies overspending to acquire them.
• Blending new and returning customers in acquisition cost. Returning buyers make acquisition look cheaper than it is. Count new customers only.
• Assuming repeat behaviour instead of measuring it. Use cohorts of real customers, not a hopeful average. If you don't yet have a year of data, use the shortest window you can measure and say so.
• Using average acquisition cost to plan growth. Plan on the marginal customer, not today's average.
• Ignoring discounts on repeat orders. Win-back offers and loyalty discounts come out of repeat-order contribution.

How unit economics fit with your other KPIs

Unit economics sit at the centre of the KPI tree. Contribution margin feeds them. Payback and lifetime value come out of them. Revenue per visitor and repeat purchase rate are the levers that move them. Our guide to ecommerce KPIs maps how all of these connect and how often to check each one.

No universal benchmark tells you whether your unit economics are good. A store selling a once-a-year product and a store selling a monthly consumable can both be healthy on very different numbers. What matters is the three tests: does each customer pay back, does it happen inside your cash cycle, and does it still hold when you spend more.

If you've run the example with your own numbers and aren't sure which lever to pull first, book a call and we'll work through it with you.