ონლაინ მაღაზია / Online Store: Measure What a Customer Costs You (CAC)

You spent money on ads, the orders came in — and you still cannot say whether you are making a profit or a loss. This is the most common situation in the first months after opening an online store: you can see the revenue, you can see the costs, but those two numbers never actually touch each other. At the end of the month there is less money in the bank than you expected, and you cannot identify the reason why.

One single measurement builds the bridge between those two numbers — the cost of acquiring a customer, known in the international literature as CAC (customer acquisition cost). It answers exactly one question: how much did you pay in order to get one person to buy from you. In the guide this step sits after building the shop and launching your first ads — at the point where the money has already gone out and you need an answer.

What CAC is and what it is not#

CAC is your total acquisition cost, divided by the number of new customers that this cost brought in. Two words in that sentence are decisive.

Total — meaning not just the advertising budget. If you paid a photographer, if you took out a subscription to a paid tool, if you gave a product away to a blogger — all of that is acquisition cost, even if it does not appear on a single invoice.

New — meaning not every order. If an existing customer came back during the same month and bought a second time, that person is not new and does not belong in the denominator of your CAC. Otherwise the number flatters itself, and you will conclude that acquisition is cheap when in reality you are counting a loyal buyer as an acquisition.

CAC is not the total cost of your shop per order. The cost of the product, the delivery, the packaging and the platform subscription form a separate group — those are worked through in the lesson on margin and unit economics. CAC measures only what you paid for attention, not what you paid to fulfil the order.

The formula#

CAC = acquisition cost (in a period) ÷ number of new customers (in the same period)

The formula is so simple that all of the difficulty moves to two other places: what you decide to count as a cost, and which period you take.

Let the period be one month, or — if you are still working with a small budget — one week. What matters is that you take the numerator and the denominator from the same window. If you divide October's spending by September's orders, the number you get means nothing at all.

What belongs in "acquisition cost"#

Write these costs down before you divide anything — this is exactly where the difference hides between a CAC that makes you feel good and a CAC that tells you the truth:

The advertising budget — across every channel, added up.
Content production — photos, video, copy, if you are paying money for them.
Paid tools that exist purely to serve acquisition.
The cost of collaborations — a product given away, or a fixed fee.
Any discount you offered, if its purpose was to bring in a new buyer. A 10% coupon is money, simply deducted from the revenue side instead of added to the cost side.
Your own hours. This is the most frequently forgotten cost and the hardest one to put a price on. If you are not yet attaching a rate to your time, at least write down how many hours you spent — you will need that number later, when you decide which channel to double down on.

The platform subscription and the delivery cost do not belong here. They are costs of fulfilling an order, and they are counted separately in the lesson on forgotten costs.

The only comparison that matters#

On its own, CAC tells you nothing. Is 30 GEL expensive or cheap? Only one other number decides that: how much stays in your pocket from a single order after you have paid for the product, the delivery and the packaging.

In other words: CAC < margin per order. If that inequality does not hold, you are losing money on every new order, and spending more on advertising accelerates the loss rather than correcting it.

For example, suppose that over one month you have spent 300 GEL on advertising and another 100 GEL on photographs — 400 GEL in total. During that month, 16 new people bought from you. CAC = 400 ÷ 16 = 25 GEL. Now take the other side: you buy the product for 40 GEL, you sell it for 95 GEL, and delivery plus packaging comes to 15 GEL — so your margin on one order is 40 GEL. 40 − 25 = 15 GEL left per customer. This works.

Now change one number: the same 400 GEL brought in 8 people instead. CAC = 50 GEL, the margin is still 40 — so every new order eats 10 GEL. Revenue grows while the bank account empties. This is precisely the situation that goes unnoticed for months without measurement.

You do not need to do this arithmetic by hand. Enter the purchase price, the selling price and the delivery cost into the margin calculator and you will get the amount left on a single order — then you compare it against your CAC.

Measure it per channel, not in aggregate#

An overall CAC tells you whether the whole thing works, but it does not tell you what works. Two channels can easily be balancing each other out: one excellent, one catastrophic, with an average that looks perfectly acceptable.

So record the spending separately for each channel, and when an order comes in, ask the simplest possible question — "how did you find us?". You do not even need an analytics system for this: one optional field in your shop's checkout form, or one question in a DM, is enough at the early stage. This habit works together with the article on advertising formats: there you choose what to try, here you measure what came of it.

What repeat purchases change#

Everything above was about the first order. If your product is the kind a customer buys again, then you should compare your CAC not against the margin of a single order, but against the total margin of that customer over time.

That does change the picture — but only once repeat purchasing is something you have actually measured. Until you have collected that data, work to the strict rule: CAC must be covered by the very first order. Relying on repeat purchases before you hold them as a figure is optimism, not calculation.

Common mistakes#

Counting only the advertising budget. Your CAC then comes out two or three times lower than it really is.
Putting every order in the denominator, repeat purchases included.
Comparing CAC against the selling price instead of the margin. A 95 GEL product does not "absorb" a 50 GEL CAC if there are only 40 GEL of margin inside it.
Deciding on the basis of one bad day. On a small budget the number jumps around; wait for at least a week of data.
Not counting your time. If you spend 20 hours a week on social media, that free channel is not free.

Your step this week#

Open a spreadsheet and write three columns: period, acquisition cost, new customers. Fill it in with last week's data — approximately is fine, from memory is fine. Divide, and you have your first CAC. Then write the margin left on one order next to it, and see which of the two numbers is larger.

That one spreadsheet will then make two real decisions for you next week: whether to raise or cut the budget, and whether to change your price or your channel.

This measurement needs a page where the order actually happens. On Sellit a shop is assembled on a ready-made template — the commission on sales is 0% on every plan, and you can try it free for 30 days without entering a card (source: sellit.ge/llms.txt). That simplifies your CAC arithmetic: it is one cost fewer that you have to account for.

Taxes and customs clearance are not the subject of this article — they are covered on a separate, hand-written page.