What's the difference between CPA and CAC?

CPA measures the cost per acquisition from a specific campaign or channel. CAC measures your total acquisition cost across all marketing. CPA is tactical (optimize individual campaigns), CAC is strategic (assess overall business health).

What's a good CPA for ecommerce?

Your target CPA should be less than your gross profit per order for first-order profitability. If your AOV is $100 with 50% margins, your max CPA for break-even is $50. Aim for 30-50% below that for healthy profitability.

Should I pause campaigns with high CPA?

Not necessarily. Consider the customer's downstream value. A $100 CPA on customers with $400 LTV is excellent. Also, prospecting campaigns naturally have higher CPAs—they're filling your retargeting pool.

Core Metrics & KPIsCPA

Cost Per Acquisition

Q: How do you calculate CPA?

CPA = Total Campaign Spend / Number of Acquisitions

The cost of acquiring a specific action through a particular campaign or channel—such as a purchase, sign-up, or lead.

1 min readLast updated Apr 2026

Formula

CPA=Total Campaign Spend/Number of Acquisitions

Example: Brand CPA = $2,000/10 = $200 | Retargeting CPA = $1,500/45 = $33 | Lookalike CPA = $3,000/30 = $100

The cost of acquiring a specific action through a particular campaign or channel—such as a purchase, sign-up, or lead.

Why It Matters

CPA gives you campaign-level clarity that CAC can't provide. While CAC tells you your overall acquisition efficiency, CPA reveals which specific campaigns, ad sets, and creatives are actually working. This granularity is essential for scaling winners, cutting losers, and optimizing your marketing mix in real-time.

Formula

CPA=Total Campaign Spend/Number of Acquisitions

Example: Brand CPA = $2,000/10 = $200 | Retargeting CPA = $1,500/45 = $33 | Lookalike CPA = $3,000/30 = $100

Practical Example

Scenario

A footwear brand runs three Meta campaigns: Brand Awareness ($2,000, 10 purchases), Retargeting ($1,500, 45 purchases), and Lookalike ($3,000, 30 purchases).

Calculation

Brand CPA = $2,000/10 = $200 | Retargeting CPA = $1,500/45 = $33 | Lookalike CPA = $3,000/30 = $100

Result

Retargeting has the lowest CPA at $33, but Lookalike at $100 is bringing in new customers. Brand at $200 CPA needs creative optimization or reduced spend.

In-Depth Explanation

Unlike CAC, CPA is channel-specific and campaign-specific, allowing granular analysis of individual marketing efforts.

Pro Tips

1Set different CPA targets for prospecting vs. retargeting. Prospecting should allow 2-3x higher CPA because those customers have higher lifetime value potential.
2Track CPA by creative, not just campaign. Often one ad in a campaign drives 80% of results at half the CPA.
3Compare CPA to first-order AOV. If CPA exceeds your gross profit on first order, you're relying on repeat purchases to break even.
4Monitor CPA trends daily during campaign launches—catch runaway costs before they drain your budget.

Common Mistakes to Avoid

Conflating CPA with CAC. CPA is campaign-specific; CAC includes ALL marketing costs. A low CPA doesn't mean low CAC if you have agency fees, creative costs, etc.

Optimizing for lowest CPA across all campaigns without considering customer quality. Cheap acquisitions that never repurchase aren't valuable.

Using the same CPA target across channels. Search (high intent) should have lower CPA than TikTok (discovery).

Frequently Asked Questions

Related Tools

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Related Terms

Customer Acquisition Cost

CAC

The total cost of acquiring a new paying customer, including all marketing and sales expenses divided by the number of new customers acquired over a specific period.

Return On Ad Spend

ROAS

The revenue generated for every dollar spent on advertising.

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