Profit & margins
Customer acquisition cost and CAC payback
Customer acquisition cost (CAC) is the average amount you spend to win one new customer. You calculate it by dividing your acquisition spend by the number of new customers in the same period. CAC payback then tells you how long a customer takes to earn that cost back in gross profit.
The customer acquisition cost (CAC) formula
CAC = Acquisition spend ÷ New customers acquired
- Acquisition spend
- what you spent to win new customers in the period
- New customers acquired
- first-time buyers in the same period
Count only new customers. Including repeat buyers makes CAC look lower than it really is.
Blended vs paid CAC
The answer depends on what you count:
Worked example: one monthExample numbers
| Input | Value |
|---|---|
| Paid ad spend | $12,000 |
| New customers attributed to ads | 300 |
| Total marketing spend (ads, influencers, affiliates) | $18,000 |
| All new customers, from every channel | 500 |
- Paid CAC = $12,000 ÷ 300 = $40
- Blended CAC = $18,000 ÷ 500 = $36
- Paid CAC shows whether your ad campaigns are efficient. Use it to manage ad budgets.
- Blended CAC includes customers from organic search, word of mouth and email. It shows what growth really costs the business.
When paid CAC rises but blended CAC holds steady, your organic channels are carrying more of the load. When both rise, acquisition is getting more expensive overall.
CAC payback period
CAC on its own doesn't tell you whether a customer is worth it. Payback does.
CAC payback (months) = CAC ÷ Monthly gross profit per customer Orders to pay back = CAC ÷ (AOV × Gross margin)
Continuing the example, with a paid CAC of $40, an AOV of $75 and a 45% gross margin:
- Gross profit per order = $75 × 45% = $33.75
- Orders to pay back = $40 ÷ $33.75 = 1.2 orders
- If a typical customer orders 0.4 times a month (about once every 2.5 months), monthly gross profit per customer = $33.75 × 0.4 = $13.50
- Payback = $40 ÷ $13.50 = about 3 months
The calculator measures payback in orders. Divide by how often customers order to convert it to months.
LTV:CAC
Lifetime value (LTV) is the gross profit a customer brings in over their whole relationship with you. Comparing it with CAC shows the return on acquisition spend:
LTV = Gross profit per order × Orders per customer over their lifetime LTV:CAC = LTV ÷ CAC
If customers in the example place 4 orders on average, LTV = 4 × $33.75 = $135, and LTV:CAC = $135 ÷ $40 = 3.4. Each dollar spent acquiring a customer comes back as $3.40 of gross profit over time.
Use LTV carefully: it's a forecast, and it's easy to overestimate for a young store with little repeat-purchase history.
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Blended CAC hides big differences between channels. Break it down using the same month as the example above:
| Channel | Spend | New customers | CAC |
|---|---|---|---|
| Google Ads | $7,000 | 200 | $35 |
| Meta ads | $5,000 | 100 | $50 |
| Influencers and affiliates | $6,000 | 60 | $100 |
| Organic, email and referrals | $0 direct spend | 140 | — |
| Total | $18,000 | 500 | $36 blended |
The paid ad channels together give the $40 paid CAC ($12,000 ÷ 300). Influencers look expensive here, but check whether those customers buy more often or spend more before cutting the channel. CAC is only half the picture; payback is the other half.
Common CAC mistakes
- Counting returning customers as new. It makes CAC look far cheaper than it is.
- Mismatched periods. Spend from one month and customers from another give a meaningless number, especially around big promotions.
- Leaving out first-order discounts. A 20% welcome discount is part of what it costs to win that customer.
- Trusting only platform-reported conversions. Ad platforms can over-credit themselves. Cross-check against new customers in your store's own data.
- Judging CAC without margin. A $50 CAC is cheap for a $200 order with a 60% margin, and ruinous for a $30 order with a 30% margin.
How to lower CAC
- Cut campaigns that don't break even. The Ad Profit Leak Score shows whether ads cover their cost after margin.
- Improve conversion rate. Better product pages and faster checkout lower the cost of each customer, not just each click.
- Raise first-order value with bundles and thresholds, so payback comes sooner. See the guide to average order value.
- Grow organic channels: email capture, search content and referrals bring in customers without a per-click cost.
- Retain customers. Repeat purchases make a higher CAC affordable. The guide to customer churn rate covers how to measure it.
FAQ
What costs should I include in CAC?
For paid CAC, the ad spend for the period. For blended CAC, all acquisition spend: ads, influencer and affiliate fees, promotional discounts for first orders, and, if you want the full picture, the cost of the people and tools that run marketing.
What is a good CAC?
One that the customer pays back quickly from gross profit. There's no universal number; a $60 CAC is fine for a store with high AOV and frequent repeat purchases and ruinous for one with a $25 one-off product.
How is CAC different from CPA?
CPA (cost per acquisition) usually counts the ad cost per conversion, including repeat customers. CAC counts only new customers. If many of your ad conversions are existing customers, CAC will be higher than CPA.
What is LTV:CAC?
It compares the gross profit a customer brings in over their lifetime with what it cost to acquire them. A ratio above 1 means customers pay back their acquisition cost; the higher it is, the more room you have to spend on growth.