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Cost Per Acquisition — solve for CPA, budget, or expected conversions. Free, no signup.
Sales, signups, leads — your primary goal
CPA
$40.00
$2,000.00 ÷ 50
Cost Per Acquisition is the simplest and most important performance metric: how much you paid for each conversion. Keep it well below the gross margin a customer generates and your marketing is profitable. Let it drift above that line and you're buying revenue at a loss.
| Channel | Ecommerce | Lead gen (B2B) |
|---|---|---|
| Google Search | $25–60 | $80–250 |
| Google Shopping / PMax | $15–45 | n/a |
| Meta (Facebook / Instagram) | $20–55 | $50–200 |
| TikTok Ads | $25–65 | $60–220 |
| n/a | $100–400 | |
| YouTube | $20–70 | $70–280 |
B2B CPAs scale with deal size. A $50k ACV SaaS can afford a $1,000 CPA; a $500 ACV tool cannot. Cross-reference CPA with the LTV calculator.
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CPA stands for Cost Per Acquisition — the average amount of ad spend required to acquire one conversion (a sale, signup, or lead, depending on how you define success). It's the north-star metric for performance marketers because it ties ad spend directly to business outcomes.
Divide total ad spend by the number of conversions. If you spent $2,000 on ads and got 50 conversions, CPA = $2,000 ÷ 50 = $40. This calculator lets you reverse the formula too: enter any two of the three values (cost, conversions, target CPA) and it solves for the third.
There's no universal answer — your target CPA depends on the LTV of a customer and your target LTV:CAC ratio. Generally, keep CPA below 25–33% of gross margin per customer for healthy unit economics. Ecommerce typical CPA runs $20–60; B2B SaaS can be $50–400+ because customer lifetime value is higher.
CPA usually measures any conversion (lead, signup, trial). CAC (customer acquisition cost) measures only paying customers and typically includes all sales and marketing costs, not just ad spend. A lead-gen CPA might be $30 while the CAC for a converted paying customer could be $300.
Search intent (Google Search Ads) usually delivers lower CPAs than interruption channels because users already have buying intent. Retargeting is usually the lowest CPA channel because audiences already engaged with your brand. Cold prospecting on Meta or TikTok runs higher CPAs but is necessary for top-of-funnel growth.
Four main levers: improve creative (better hooks, clearer offers), tighten audience targeting (lookalike + high-intent interests), improve landing page conversion rate (1% lift in CR cuts CPA by ~1%), and optimize for cheaper conversions (some channels undervalue micro-conversions). Bid lowering alone rarely works — it usually cuts volume without cutting CPA.
