E-Commerce Unit Economics: A Guide to CAC, LTV and Contribution Margin

Web and E-Commerce, 10 min read. By Sefa Aydın. Last updated: September 16, 2026

E-commerce brands that pass 1 million TL in monthly revenue while their bank balance stays flat share the same problem: they do not know what they earn per order. Ad spend goes up, orders go up, revenue goes up, and at the end of the month there is still not enough cash. That is not a sales problem. It is a unit economics problem.

Unit economics breaks the business down to one order and one customer and asks whether there is profit at that level. Below, we build the contribution margin, CAC and LTV math on a TL example, show you how to read the LTV/CAC ratio and the payback period, and then list six moves that grow your margin.

What Are Unit Economics and Why Should You Track Them Instead of Revenue?

Unit economics is the calculation of what each order and each customer earns or costs your business. Total revenue tells you scale but not direction. If you ship 1,000 orders and lose 30 TL on every one, you sink faster the more you grow, and your revenue chart will never show it.

Three numbers carry the entire picture: contribution margin per order, customer acquisition cost (CAC) and customer lifetime value (LTV). A brand that knows all three can calculate how far it can scale its ad budget, which product should be pulled from ads and how deep a discount it can survive. A brand that does not know them is guessing.

How Do You Calculate Contribution Margin per Order?

Contribution margin is what remains from an order's revenue after you subtract every variable cost tied to that order. Fixed costs such as rent, salaries and software are excluded, because they do not change with order volume. The table below shows the math for a cosmetics brand with an average order value of 900 TL excluding VAT:

Advertising cost is not in this table, because it is calculated separately at the customer level as CAC.

A 48% contribution margin sounds good, but on its own it tells you nothing. You cannot talk about profit until you see how much of that 430 TL goes to acquiring the customer. Test your own numbers with the e-commerce profitability calculator, and do not skip the returns allowance: an 8% return rate doubles shipping cost for most brands.

What Is CAC and How Do You Calculate It?

CAC, or customer acquisition cost, is the total amount you spend to win one new customer. You find it by dividing total acquisition spend by the number of new customers. Two words are critical here: "total" and "new".

Total spend

Media spend alone is not CAC. Agency fees, creative production, influencer payments and ad tools are acquisition costs too. The brand in our example spends 150,000 TL a month: 120,000 TL on media, 20,000 TL on the agency and 10,000 TL on creative.

New customers

The denominator should be first-time buyers, not all orders. Counting repeat orders from existing customers makes CAC look lower than it is. This brand has 450 orders a month, but only 300 of them come from new customers. CAC = 150,000 / 300 = 500 TL.

This is where the first warning sign appears: contribution per order is 430 TL, while the cost per new customer is 500 TL. So every new customer loses you 70 TL on the first order. That is not a disaster by itself, but it becomes one if the customer never comes back. We cover ways to bring CAC down in detail in our article on reducing customer acquisition cost.

How Do You Calculate LTV?

LTV is the total contribution margin a customer generates over their entire relationship with you. It uses contribution margin rather than revenue, because the number you compare against CAC has to be in the same unit. The formula is:

LTV = Average order value x Annual order frequency x Customer lifespan (years) x Contribution margin rate

In the example brand, a customer places 1.8 orders a year on average and stays active for 1.5 years on average. LTV = 900 x 1.8 x 1.5 x 0.48 = 1,166 TL. Pull frequency and lifespan from your order history: the average number of orders from customers who bought in the last 12 months gives you frequency, and the average time between first and last order gives you lifespan. If you do not have this data yet, you can get a starting figure with the customer lifetime value calculator.

A warning: optimism is the most expensive mistake in an LTV calculation. If the assumption "customers stay for 5 years" has not been measured, use 1 year. A budget decision based on a conservative LTV will at worst grow you too slowly. A decision based on an optimistic LTV will sink you.

Validating with cohorts

The LTV formula is an average, cohort analysis is reality. Take the customers who placed their first order in January as one group and measure the total contribution of that group after 3, 6 and 12 months. If the group cannot get close to the formula's 1,166 TL within 12 months, the frequency or lifespan assumption in the formula is too optimistic. A cohort table also shows you which month's customers are worth more, and customers acquired during discount periods often have a noticeably lower LTV.

LTV/CAC Ratio and Payback Period

An LTV/CAC ratio of 3:1 or higher is the widely accepted threshold for healthy unit economics. In the example brand, 1,166 / 500 = 2.3. In other words, every 1 TL of acquisition cost produces 2.3 TL of contribution over the customer's lifetime. There is no loss, but the room left to cover fixed costs and growth investment is thin.

Here is how to read the ratio:

• Below 1:1: Every customer loses you money. Scaling ads scales the loss, so fix margin and CAC first.
• Between 1:1 and 3:1: You survive, but you do not generate growth capital. The example brand is here.
• 3:1 and above: Healthy, and you can increase your ad budget with confidence.
• Above 5:1: You are probably underinvesting in ads and losing market share.

The second indicator is the payback period, meaning how many months it takes for the contribution from a customer to earn back the CAC. Monthly contribution = 430 TL x 1.8 / 12 = 64.5 TL. Payback = 500 / 64.5 = roughly 7.8 months. In e-commerce, under 6 months is comfortable and over 12 months is considered dangerous for cash flow. At 7.8 months the example brand is on the edge: every new customer ties up cash for eight months.

How High Can Your CAC Go While You Scale?

The real job of unit economics is to put a ceiling on your ad budget: the maximum acceptable CAC is one third of LTV. In the example brand that is 1,166 / 3 = 389 TL. Since today's CAC is 500 TL, the brand should not increase its budget. It should first bring CAC below 389 TL or lift LTV above 1,500 TL.

The second limit is first-order break-even: once CAC exceeds the contribution margin per order of 430 TL, every new customer burns cash. Brands with tight cash flow work to this limit, while well-capitalized brands work to the LTV/3 limit. A brand that knows both sets its ad scale not by asking "do we have the budget?" but by asking "up to what CAC are we profitable?". Calculating these two limits takes five minutes and ends most ad budget debates.

If revenue is growing while your cash shrinks, the problem is not sales. It is the economics of each order.

6 Moves That Grow Your Margin

To move the example brand from 2.3 to above 3:1, you have to lower CAC or raise LTV. Here are six moves and the effect of each one on the example:

1. Raise your average order value. Using a free shipping threshold, two-packs and complementary product suggestions to lift 900 TL to 1,050 TL pushes contribution margin from 430 to roughly 515 TL, and the 70 TL loss on the first order turns into profit.
2. Increase repeat purchase frequency. Lifting annual frequency from 1.8 to 2.4 with post-purchase email and WhatsApp flows, replenishment reminders and a loyalty program raises LTV from 1,166 to 1,555 TL. We explain the setup in our article on email marketing automation.
3. Lower your return rate. If a size chart, real product photos and a clear description bring returns down from 8% to 5%, roughly 8 TL of contribution per order comes back. It looks small, but across 5,400 orders a year it is 43,000 TL.
4. Renegotiate shipping and payment contracts. As monthly volume grows, the unit price of shipping and your POS commission drop. Collecting quotes once a year saves 15 to 25 TL per order.
5. Manage your product mix by margin. Shifting ad budget from a product with a 30% margin to one with a 55% margin nearly doubles contribution at the same CAC. You cannot make this decision without a product-level margin table.
6. Lower your CAC. Bringing CAC from 500 down to 400 TL through creative testing, audience tightening and conversion rate improvements on its own moves the LTV/CAC ratio from 2.3 to 2.9.

When two of these moves are applied together, the example brand comfortably clears 3:1. You will find the system behind loyalty and repeat purchases in our article on customer loyalty and CRM strategies.

Implementation Checklist

To build your unit economics table this month, work through these steps in order:

• Pull the average order value excluding VAT from the last 3 months of orders.
• Subtract product, shipping, fees, packaging and the returns allowance to get contribution margin per order.
• Divide total acquisition spend, including media, agency and creative, by the number of new customers to get CAC.
• Measure annual frequency and customer lifespan from your order history instead of estimating them.
• Calculate LTV on contribution margin, then work out the LTV/CAC ratio and the payback period.
• If the ratio is below 3:1, apply two of the six moves before increasing your ad budget.
• Update this table every month and make your ad decisions from it.

Once your unit economics are in place, the ad budget debate is over, because the numbers tell you up to what CAC you can grow profitably. If you want to work out the per-order economics of your own brand together, take a look at our e-commerce marketing approach or contact us for a free consultation.

Related articles

• How to reduce customer acquisition cost (CAC)
• How to increase average order value
• What is break-even ROAS
• How to reduce your e-commerce return rate

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