Customer acquisition cost calculator
One row per channel, spend and new customers in each, and you get the cost per customer on every channel plus the blended figure across all of them. Add your average order value to see what the first order pays back.
Verified August 22, 2026
Blended cost per customer
$40.00
$10,000 of spend across 250 new customers
A first order contributes $36.00 and costs $40.00 to win, so the first order loses money. It takes 2 orders from a customer to pay the acquisition back.
Cheapest channel first
- Email and other $20.00
- Google $37.50
- Meta $50.00
- Total spend
- $10,000
- New customers
- 250
- First order contributes
- $36.00
- Orders to pay back CAC
- 2
Acquisition only. Retention spend on customers you already have belongs in a different number.
How customer acquisition cost is calculated
Spend divided by new customers. That is the whole formula, and the difficulty is never the division. It is agreeing what goes on top and what goes underneath. Acquisition spend means everything you paid to bring in people who had never bought from you: media spend, the agency retainer, the creative, the affiliate commission on a first order. New customers means first-time buyers, not orders, so a customer who bought three times in the period counts once.
CAC = spend ÷ new customers
6,000 ÷ 120 = 50.00 on Meta
10,000 ÷ 250 = 40.00 blended
Run it per channel and the average stops hiding things. The three default rows above spend $10,000 between them and average $40.00 a customer, and not one channel is anywhere near $40.00. One costs $50.00, one costs $37.50, and one costs $20.00. The blended figure is the only one you can trust as a total, and it is the least useful one for deciding where the next dollar goes.
Cheapest customer at the top. Same three channels, same month, and the top one costs a fraction of the bottom one.
Keep both numbers. Per-channel CAC only sees the customers its own attribution claimed, so the rows will usually sum to fewer customers than your store actually gained. Blended CAC divides everything you spent by everyone you gained, including the people no platform took credit for, which is why it is the blended total that holds even when it is the less flattering one.
CAC is not the number in your ad account
Google Ads reports average cost per action, which it calculates by dividing the total cost of conversions by the total number of conversions. A conversion is whatever you told it to count, so that column may be measuring purchases, or it may be measuring newsletter signups and add-to-carts alongside them. It also counts a repeat buyer as a conversion, and a customer acquisition cost should not.
So the platform figure runs low twice over: it counts orders your existing customers placed, and it ignores every dollar you spent that has no conversion tag attached. Take the spend from the platform, take the new-customer count from your store, and do the division yourself. The rows above are built for exactly that mix.
The same discipline applies to what an order is worth. Get the average order value from your store rather than from the ad platform, on the definition your reports actually use, which the AOV calculator spells out. Then work out what is left of that order after costs, starting from the goods themselves in the COGS calculator.
What a first order actually pays back
A CAC is a number without a verdict until you put it next to what an order contributes. Contribution per unit is the selling price minus the variable cost of that unit, so at a 45% contribution margin, meaning 45% left after the goods, the shipping you absorb and the payment fee, an $80.00 order contributes $36.00. Against a $40.00 blended CAC, the first order is $4.00 short. The customer is not unprofitable. The first order is.
first-order contribution = AOV × contribution margin
80.00 × 0.45 = 36.00
orders to pay back = CAC ÷ contribution, rounded up
40.00 ÷ 36.00 = 1.11, so 2 orders
Contribution adds up order by order. It clears the acquisition cost on the second one.
Rounding up is the point. You cannot collect 11% of an order, so payback lands on the second one or it does not land at all. That turns an abstract ratio into a question with a real answer: does this customer come back? If your repeat rate says most of them do not, a CAC above first-order contribution is not an investment, it is a loss with a longer settlement date.
Ratios of lifetime value to CAC come from software. David Skok's SaaS Metrics 2.0 put the best SaaS businesses above 3 times, and called profitability anemic when payback runs beyond twelve months. That is a subscription business with near-zero marginal cost, and a store shipping physical goods is not one, so treat those figures as where the convention came from rather than as your target.
The local test needs no benchmark. Contribution per order against CAC gives you the number of orders. Your own repeat rate says whether customers place that many. Everything else is somebody else's business quoted at you. The ROAS calculator runs the same logic from the ad side, returning the return on ad spend your margin forces you to clear.
When somebody else converts the customer you paid for
Your ads teach people what your product looks like and what it is called. Some of them go and search that name, or that image, and land on a listing that uses your photographs at a lower price. Your spend does not change and your new-customer count does, so CAC scales by one divided by one minus the diverted share. Call that share d.
diverted CAC = CAC ÷ (1 − d)
40.00 ÷ (1 − 0.10) = 44.44
40.00 ÷ (1 − 0.20) = 50.00
d is your number, not ours, and nobody has measured it credibly for any single store. The arithmetic is still worth knowing, because it moves fast: a fifth of the demand landing somewhere else takes a $40.00 CAC to $50.00 while every dashboard you own reports the campaign as unchanged. Contribution per order stays at $36.00 the whole time, so the payback quietly moves out.
The cheap version of the check is finding out whether anybody is running listings with your product photographs on them. Knockoff watches your catalog's photos across Amazon, Temu, eBay, Etsy, AliExpress, Walmart and the open web, confirms each match against the seller's own listing gallery, and hands you a finished case to approve. See what goes into a case, or run a scan and see which of your products are being copied today.
Common questions about CAC
How do you calculate customer acquisition cost?
+
Divide what you spent to win customers in a period by the number of new customers you won in it. $10,000 of spend and 250 new customers is a $40.00 CAC. Do it once per channel to see which channel is carrying the average, and once across everything for the blended figure.
What is a good CAC?
+
Compare it to what a first order contributes, not to somebody else's number. At an $80.00 average order and a 45% contribution margin, a first order contributes $36.00, so a $40.00 CAC loses money on order one and needs a second order to pay back. Anyone quoting a good CAC in dollars is quoting a different business.
Is CAC the same as CPA?
+
No. Google Ads calculates average cost per action as the total cost of conversions divided by the number of conversions, and a conversion can be any action you told it to count. CAC counts new customers only, across every channel, including the spend that has no conversion tag on it at all.
How do you calculate blended CAC?
+
Add up all acquisition spend for the period, then divide by every new customer you got in it, including the ones no channel claimed. Blended CAC is always the blended number, because per-channel figures only see the customers their own attribution saw.
Sources
- Google Ads Help, average cost per action, for cost per action being the total cost of conversions divided by the total number of conversions
- Shopify, break-even analysis, for contribution margin per unit as the average selling price minus the variable cost per unit
- Shopify Help Center, sales reports, for the average order value definition the payback figures assume
- David Skok, SaaS Metrics 2.0, for the ratio above 3 times and the twelve-month payback convention, both stated there about SaaS businesses
Every figure on this page was read from the source beside it and verified August 22, 2026. The CAC, blended CAC, contribution and payback arithmetic is arithmetic and belongs to nobody. No benchmark CAC is quoted here, because no dated primary source publishes one for ecommerce.
