The total affiliate program cost divided by the number of new customers acquired through the affiliate channel. CPA is the primary efficiency metric for evaluating affiliate program economics in the context of customer acquisition goals. Formula: Total Affiliate Program Cost ÷ New Customers Acquired = CPA. Total affiliate program cost includes: affiliate commissions paid; affiliate network override fees (typically 25-30% of commission); program management costs (staff time, agency fees); technology and tool costs. New customers acquired: only first-time buyers are counted in affiliate CPA for new customer acquisition goals; returning customers who convert through affiliate links are excluded from this calculation because they represent retention, not acquisition. Benchmark by category: financial services: $50-$250 CPA is common given high customer LTV; subscription software: $20-$100 CPA; consumer goods: $15-$60 CPA; luxury goods: $80-$300 CPA. How to use affiliate CPA: compare affiliate CPA against other acquisition channels (paid search CPA, paid social CPA, influencer CPA) to evaluate relative efficiency; if affiliate CPA is $45 and paid search CPA is $90, affiliate has a meaningful cost advantage for acquiring equivalent new customers; if affiliate CPA is $45 and SEO-driven organic CPA is $12, assess whether affiliate is reaching distinct audiences or competing for the same buyers as organic. CPA vs. ROAS: ROAS (Return on Ad Spend) measures revenue return on commission investment; CPA measures the cost to acquire a new customer; both are necessary; ROAS alone can be misleading if coupon and cashback publishers are inflating attributed revenue without incrementally acquiring new customers.
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