CPA Calculator
The Metric That Actually Reflects Business Outcomes
Clicks and impressions measure exposure, but CPA — cost per acquisition — measures what you actually paid for a completed outcome: a sale, a signup, an app install, whatever counts as a conversion for the campaign. Two campaigns with identical CPC can have very different CPA if one converts visitors at a meaningfully higher rate, which is why CPA is usually the number that determines whether a campaign is profitable.
The Formula
CPA = Total Cost / Total Conversions
Total Cost = CPA × Total Conversions
Total Conversions = Total Cost / CPA
Total Cost = CPA × Total Conversions
Total Conversions = Total Cost / CPA
Where This Calculation Matters
- Setting a profitable bid ceiling — if a customer is worth $80 in profit, a CPA target below that figure keeps the campaign profitable.
- Comparing acquisition channels — CPA lets you compare paid search, paid social, and display on the same basis regardless of how each platform prices clicks or impressions.
- Forecasting conversions from budget — given a budget and a historical CPA, the find-conversions mode estimates expected volume before a campaign launches.
- Justifying spend to stakeholders — CPA translates ad spend directly into the currency a business cares about: acquired customers or leads.
Worked Examples
| Total cost | Conversions | CPA |
|---|---|---|
| $2,000 | 80 | $25.00 |
| $5,000 | 125 | $40.00 |
| $10,000 | 400 | $25.00 |
How to Use This Calculator
- Choose which value to solve for: Find CPA, Find Total Cost, or Find Total Conversions.
- For Find CPA, enter total cost and total conversions.
- For Find Total Cost, enter CPA and total conversions.
- For Find Total Conversions, enter total cost and CPA.
- Select Calculate to get the result.
Related Calculations
Check overall return with the ROAS Calculator, or trace acquisition cost back to lead generation with the Cost Per Lead Calculator.