Cost per acquisition — what you pay to acquire one paying customer. Compare to contribution margin to know if ads pay back.
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CPA (Cost Per Acquisition) is what you pay in ad spend to acquire one paying customer. If you spent $600 on ads and got 40 orders, your CPA is $15. Compare CPA to your contribution margin per unit: if CPA is lower than contribution, you're profitable. If higher, you're losing money on every order.
CPA = ad spend ÷ number of conversions
Then compare: Net per order = contribution per unit − CPA
CPA and ROAS answer different questions. ROAS asks "how much revenue did I get per ad dollar?" CPA asks "how much did I spend to acquire one customer?" They're inverses of each other if AOV is constant. Use ROAS when comparing products with different price points; use CPA when comparing campaigns with the same product. Read our ROAS vs CPA vs CPC article for the full breakdown.
| Input | Value |
|---|---|
| Ad spend | $600.00 |
| Conversions | 40 orders |
| Contribution per unit | $10.54 |
| CPA | $15.00 |
| Net per order after CPA | −$4.46 |
| Campaign profit | −$178.40 |
| Status | Below break-even |
This campaign is losing $4.46 per order. CPA ($15) exceeds contribution per unit ($10.54). You need to either lower CPA (better creative, better targeting) or raise contribution (higher price, lower costs).
Calculate actual ROAS from ad spend and revenue, and compare it to your break-even ROAS to see if a campaign is profitable.
Net profit on a campaign after ad spend, product costs, and fees. Shows whether your ads actually make money.
Contribution margin per unit and as a ratio — what each sale contributes toward covering fixed costs and profit.
These three ad metrics answer different questions. Mixing them up is the most common beginner mistake in the r/dropshipping threads.
Break-even ROAS is the floor, not the target. Reddit consensus and real campaign math show what "profitable" really means.