CPA Calculator — Cost Per Acquisition
How much does each new customer, lead, or sale really cost you? Compute CPA five ways, convert it to ROAS, and find the break-even CPA your margins can actually afford.
CPA from ad spend & conversions
The classic definition: total campaign cost divided by the number of acquisitions it produced.
CPA = Total Ad Spend ÷ Acquisitions · ROAS = Revenue ÷ SpendCPA from CPC & conversion rate
Handy when you know your click costs and your site’s conversion rate, but not total spend yet.
CPA = CPC ÷ Conversion Rate (as a decimal) · Max CPC = Target CPA × CVRTarget CPA ↔ ROAS converter
Translate between the CPA your budget people speak and the ROAS your ad platforms speak.
Target CPA = AOV ÷ ROAS · Required spend = Target CPA × Desired conversionsBreak-even CPA & unit economics
A CPA is only “good” relative to your margins. Find the most you can pay per acquisition before profit turns negative.
Break-even CPA = AOV × Gross Margin · Profit per acquisition = Break-even CPA − Actual CPACompare campaigns
Same conversion definition, same period — see which campaign buys customers cheapest.
Worked example
A store spends $4,000 on ads and gets 160 purchases:
| Step | Math | Result |
|---|---|---|
| CPA | $4,000 ÷ 160 | $25.00 per purchase |
| AOV | $12,800 revenue ÷ 160 | $80.00 |
| ROAS | $12,800 ÷ $4,000 | 3.2× (320%) |
| Break-even CPA (55% margin) | $80 × 0.55 | $44.00 |
| Profit per acquisition | $44.00 − $25.00 | $19.00 — profitable |
What is a good CPA?
Illustrative guidance — not a benchmark database. A CPA is only good relative to what each acquisition is worth to you.
| Business type | Rule of thumb |
|---|---|
| E-commerce (one-time purchase) | CPA should sit well below your break-even CPA (AOV × margin). Many stores aim for actual CPA at 50–70% of break-even so profit survives returns and fees. |
| Lead generation (B2B / services) | Judge cost per lead by your close rate: effective cost per customer = CPA ÷ close rate. A $30 lead at a 20% close rate is really a $150 customer. |
| Subscription / SaaS | Compare CPA against customer lifetime value, not first-month revenue. A common bar is LTV:CAC of 3:1 or better. |
| Mobile apps | Install CPA means little alone — weigh it against retention and in-app revenue per acquired user over 30–90 days. |
Universal rule: compare CPA against break-even CPA and watch the trend. A rising CPA at flat conversion value is the metric deteriorating, whatever the absolute number.
Methodology
- CPA (basic): total ad spend ÷ number of acquisitions. Requires at least 1 acquisition — zero conversions means CPA is undefined, not zero.
- CPA from CPC & CVR: CPC ÷ (conversion rate as decimal). Follows from CPA = cost ÷ actions, CPC = cost ÷ clicks, CVR = actions ÷ clicks.
- Target CPA ↔ ROAS: target CPA = AOV ÷ ROAS. Both describe the same efficiency; platforms optimize to one, finance plans in the other.
- Break-even CPA: AOV × gross margin. At exactly this CPA, gross profit from the acquisition is zero — above it you lose money on every sale before overhead.
- All calculations run locally in your browser. No data leaves your device.
Frequently asked questions
Working the other direction? Our Conversion Rate Calculator computes CVR from visitors and conversions, with a funnel planner and revenue-lift estimator.
Free tool by NRTechStudio