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Marketing GuideThe cost per acquisition formula every marketer should know. How to calculate CPA, benchmark yours, and systematically lower it.
Cost Per Acquisition (CPA) = Total Marketing Spend ÷ Number of Acquisitions. Simple. If you spent £5,000 on ads and acquired 100 customers, your CPA is £50.
But the simple formula hides important nuances. What counts as an "acquisition"? A purchase? A qualified lead? A signup? Your CPA is only meaningful if you define acquisition consistently and tie it to revenue.
The real question is not "what is my CPA?" but "is my CPA sustainable?" Compare CPA to Customer Lifetime Value (LTV). A healthy ratio is typically 1:3 or better — your customer should be worth at least 3× what you paid to acquire them.
This guide covers the formula, variations by channel, benchmarks by industry, and practical tactics to lower your CPA.
CPA = Total Campaign Cost ÷ Conversions. Include all costs: ad spend, agency fees, creative production.
Calculate separately for Google Ads, Meta, SEO, email. Blended CPA hides underperforming channels.
Set targets based on margins: Target CPA = Customer Value × Target Margin %.
CPA typically measures campaign-level cost. CAC (Customer Acquisition Cost) includes all sales and marketing costs.
The golden metric. Aim for 3:1 minimum. Below 2:1 means you are likely losing money on growth.
The cost of your next customer is higher than your average. Scale decisions need marginal analysis.
Improve conversion rate, tighten targeting, test creative, optimise landing pages, cut wasted spend.
Diagnose: increased competition? Audience fatigue? Tracking issues? Seasonality? Each needs a different fix.
Calculate CPA by channel, campaign and audience. Find the outliers.
Ensure conversions are tracked accurately — bad data means bad decisions.
Pause or fix campaigns with CPA above your target. Be ruthless.
Landing page CRO often lowers CPA more than any media change.
A/B test audiences, creative and offers to find efficiency gains.
Increase budgets on proven campaigns gradually (20% increments).
It depends entirely on your margins. Ecommerce: £10–£50 typical. B2B services: £100–£500+. What matters is CPA relative to customer lifetime value.
Total SEO investment (agency + content + tools) ÷ organic conversions over the same period. SEO CPA typically decreases over time as investment compounds.
Common causes: increased competition raising CPCs, audience saturation, creative fatigue, tracking breakage, or scaling into less efficient audiences.
ROAS for ecommerce (revenue-focused). CPA for lead gen (cost-focused). Both need LTV context to set proper targets.
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