Customer acquisition cost (CAC) is the average amount you spend to gain one new customer. It helps online sellers judge whether advertising, creator partnerships, discounts and other marketing activities are producing profitable customers.
How to calculate CAC
CAC = total acquisition cost ÷ new customers acquired
If you spend $600 on ads and related promotion and gain 40 first-time customers, your CAC is $15. Include the costs that belong to the same period and campaign. Do not compare one month of advertising with six months of customers.
What belongs in acquisition cost?
Depending on your business, include:
- Paid search and social advertising
- Influencer or affiliate commissions
- Creative production made specifically for the campaign
- Marketing software and campaign fees
- Promotional discounts used to win the first order
- Agency or contractor costs
Separate general brand expenses from costs that clearly generated new customers. If a cost cannot reasonably be assigned to a campaign, record it separately rather than pretending the calculation is precise.
New customers matter
Do not divide all orders by marketing spend when the goal is customer acquisition. Repeat orders from existing customers can make CAC look artificially low. Track first-time buyers separately from returning buyers, and state whether your calculation includes refunds or cancelled orders.
For a simple first calculation, use completed first orders. As your data improves, compare CAC by channel, campaign, product and customer location.
Compare CAC with contribution profit
A $10 CAC is not automatically good or bad. Compare it with the profit available from the customer’s first order and expected future orders.
Calculate the first-order contribution after product cost, marketplace fees, payment processing, shipping, packaging, discounts and CAC. The Profit Margin Calculator helps check the margin before and after selling costs.
If your first order produces $12 before CAC and CAC is $15, you lose $3 on the first purchase. That may still be acceptable if repeat customers are common and profitable, but it is risky if most buyers never return.
CAC versus customer lifetime value
Customer lifetime value (LTV) estimates the contribution a customer generates over multiple purchases. A basic comparison is:
Maximum sustainable CAC = expected lifetime contribution − desired profit buffer
For example, if a customer is expected to generate $80 in contribution over several orders, you should not automatically spend the full $80 to acquire them. Keep a buffer for refunds, support, fulfilment changes and inaccurate assumptions.
Use your own order history where possible. Industry averages are not a substitute for knowing your repeat-purchase rate, average order value and gross contribution.
Measure each channel separately
Paid search, social advertising, email, marketplace promotions and organic search have different costs and customer intent. Report each channel separately instead of combining everything into one attractive average.
For Amazon advertising, compare CAC with advertising cost of sale and the organic sales that follow. Sellers can use the Amazon ACoS & ROAS Calculator to examine campaign efficiency, but remember that ROAS measures revenue, not profit.
For marketplace fees and commissions, check the appropriate eBay Fee Calculator or Etsy Fee Calculator before deciding what CAC you can afford.
Do not ignore discounts
A first-order discount is an acquisition cost when it is used to persuade a new customer to buy. A $5 discount on 40 new orders adds $200 to the campaign cost.
Discounts can work when they attract customers who later reorder, but they can also attract one-time bargain hunters. Compare cohorts: customers acquired with a discount versus customers acquired without one.
Common CAC mistakes
Counting clicks as customers
Clicks, views and followers are useful indicators, but they are not customers. Use completed first purchases for the main CAC calculation.
Using revenue instead of contribution
A $50 sale does not mean $50 is available to pay for acquisition. Subtract product, fulfilment, platform and payment costs first.
Ignoring refunds
Refunds and failed payments reduce the customers and revenue you actually keep. Recalculate once returns are known.
Changing the measurement period
Advertising spend today may produce orders later. Record campaign dates and use a consistent attribution window rather than comparing spend and sales from unrelated dates.
How to lower CAC
- Improve the landing or product page so qualified visitors understand the offer.
- Test stronger product images and clearer specifications.
- Retarget visitors carefully instead of paying repeatedly for the same audience.
- Use customer reviews and useful content to build trust.
- Increase average order value with relevant bundles rather than blanket discounts.
- Focus budget on products with healthy contribution margins.
The Break-Even Units Calculator can show how many additional units are needed to recover a campaign cost. That is useful when deciding whether a promotion is large enough to justify its spend.
A simple weekly CAC report
- Channel and campaign
- Total acquisition cost
- New customers
- CAC
- First-order revenue and contribution
- Refunds and cancellations
- Repeat-purchase rate
- Customer lifetime contribution
Final takeaway
CAC is useful only when it is connected to profit. Measure the real cost of acquiring new customers, separate channels, account for discounts and refunds, then compare the result with first-order and lifetime contribution. Scale campaigns that create profitable customers, not just cheap clicks.