CPA calculator
Calculate cost per acquisition for a chosen conversion event and compare it with available margin.
Last updated
Written by Madly editorial
01 / Your inputs
Run the numbers
Example figures are filled in so you can see a result straight away. Replace them with your own. Results update as you type; no data is sent or saved.
Total media spend in the same currency as your revenue.
Choose one event (purchase, qualified lead or signup) before entering its attributed count. This is not automatically new-customer CAC.
02 / Calculation
Cost per conversion
Calculated result
£25.00
Unit: £/conversion
Formula
CPA (£/acquisition) = ad spend (£) ÷ acquisitions.
How to read this
Compare cost with contribution margin or lifetime contribution, not revenue alone. Confirm whether repeat customers are included.
Assumptions
Only include acquisitions credited to the same spend and timeframe. Attribution settings can change the count.
How to use this tool
- Total the ad spend for the period you are judging.
- Count the purchases attributed to that spend in the same window.
- Enter both and read the cost per acquisition.
- Compare it with your max CPA from the max CPA calculator to see whether you are above or below the line.
Worked example
Illustrative example: £450 spent for 15 first orders gives £30 per first order.
What this measures
Define the acquisition before entering its count: an order, a new customer and an email signup are different outcomes.
Formula and units
CPA (£/acquisition) = ad spend (£) ÷ acquisitions.
Assumptions and review notes
Only include acquisitions credited to the same spend and timeframe. Attribution settings can change the count.
Compare cost with contribution margin or lifetime contribution, not revenue alone. Confirm whether repeat customers are included.
A good CPA is below your max CPA, the amount you can pay for a customer and still reach your profit goal. That figure depends on price, cost of goods, shipping, returns and whether repeat orders matter to you. Without those, any CPA is only a number. Calculate your limit first, then judge the CPA against it.
- Average order value and margin.
- Return rate.
- Attribution window and how much it counts.
- Repeat purchase behaviour for your product.
- Setting a target CPA from a competitor or a blog post rather than your margin.
- Ignoring returns and shipping when working out what a sale is worth.
- Judging CPA on three or four purchases.
- Mixing attribution windows between reports.
A closer look
Common questions.
- What is CPA?
- Cost per acquisition is the ad spend divided by the number of purchases or other target actions it produced.
- CPA or ROAS: which is better?
- They describe the same data differently. CPA suits stores with similar order values, while ROAS suits varied baskets.
- What is a good CPA?
- One lower than your max CPA. Use the max CPA calculator to find your own limit.
- Does CPA include organic sales?
- Platform CPA counts only attributed sales. Blended measures such as MER look at all revenue against all spend.
- How many purchases do I need to trust CPA?
- Enough that one extra sale does not change the picture. Treat a handful as an early signal only.