CAC calculator, with CPA and payback
CAC (customer acquisition cost) is what you spend to win one new customer: marketing spend divided by first-time customers in the same period. Spend $40,000 in a month, win 1,000 new customers, and CAC is $40.
Same ad spend, different denominator.
All marketing ÷ new customers
The full cost of a new customer, from every channel. Read it in Shopify.
Ad spend ÷ new customers from ads
What ads alone pay per first-time buyer. Decides how far ads can scale.
Ad spend ÷ purchases
Counts repeat buyers too, so it reads lower than CAC. Use it to compare ads.
Months until profit covers CAC
The first order's profit, then repeat orders, until CAC is paid back.
Profit per order = order value × margin − shipping and fees. Payback months = (CAC − profit per order) ÷ (monthly repeat rate × profit per order). LTV:CAC = lifetime profit ÷ CAC.
One month, four numbers.
$40 blended CAC
$40,000 on all marketing brought 1,000 first-time customers.
$50 paid CAC
$30,000 of that was ads, and 600 new customers came from ads.
$30 CPA
The platforms credited 1,000 purchases. 400 were repeat buyers.
3.3 months payback
An $80 order keeps $30, so $10 of CAC is left. 10% reorder monthly: $3 a month.
Why Meta's CPA looks cheaper than CAC.
- Repeat customers count as purchases.
- Two platforms can claim one order.
- View-through credit counts orders nobody clicked.
Judge the store on Shopify numbers: MER for all revenue, CAC for new buyers. Use platform ROAS and CPA to pick ads.
Three levers that move CAC.
More ads that win
Fresh hooks and formats beat ad fatigue, which pushes cost per customer up.
Creative →A page that converts
A 20% conversion lift cuts CAC 17% at the same spend.
Conversion →A bigger first order
More profit per first order shortens payback without touching CAC.
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