What is the difference between CPA and CAC?
CPA counts media spend only. CAC adds the salaries, retainers and tools that produced the campaigns, so it is always larger. If yours are equal, the CAC is missing something.
CPA Calculator
What one acquisition costs from media spend, and the ceiling your margin allows. Fill in two of the three.
Fill in any two of spend, conversions and cost per acquisition. Add your margin and the tool says whether each acquisition pays for itself.
Everything here is worked out in your browser. Nothing you type is sent anywhere, and there is no account to make.
Leave this blank to work it out from the other two.
Optional. Adds revenue and ROAS.
%
Optional. Gives the CPA ceiling one order can pay for.
Result
The numbers below are an example so the tool opens working. Replace them with yours.
How the number is worked out
- CPA here is media spend divided by conversions, which is what an ad platform reports. It leaves out salaries, agency fees and tools; the figure that includes those is CAC, and it has its own page.
- The ceiling shown against your margin is a simple one: contribution per order. The floor a campaign has to clear, with returns and variable costs in it, is worked out on the break-even ROAS page rather than approximated here.
What comes out
You will see
- Cost per acquisition from media spend
- Whichever of the three you left blank, worked out from the other two
- Revenue and ROAS, when you add an order value
- Contribution per order at your margin
- The break-even CPA one order can pay for
- A warning when your CPA sits above what an order contributes
How to use it
Three steps, and the third one is the point
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Enter spend and conversions
Media spend only, and the conversions that spend produced. Keep both from the same window.
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Leave the CPA blank, or work backwards
Enter a target CPA and a conversion count to see the budget that implies.
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Add order value and margin
That gives you the ceiling: what one order contributes is the most an acquisition can cost before it stops paying for itself.
CPA, CPL and CAC are three different numbers
They get used as if they were the same one, and the confusion is expensive. Cost per lead prices an enquiry. Cost per acquisition prices a conversion from media spend. Customer acquisition cost prices a customer including the salaries, retainers and tools that produced the campaigns.
CAC is structurally the largest of the three, and that is a definition rather than a fault. If your CPA and your CAC come out the same, something is being left out of the CAC.
This page does the middle one. The other two have their own pages, and the numbers are meant to differ.
The ceiling, and where this tool stops
The simple ceiling is contribution per order: order value times margin. Pay more than that for an acquisition and the order loses money before anything else in the business is paid for.
It is a simple ceiling on purpose. The real floor needs your return rate and your variable costs, and that calculation lives on the break-even ROAS page. Putting a second version of it here would give the site two break-even definitions and leave the reader to choose.
What this tool will do is say when you are over the line, and point at the page that works the floor out properly.
The tool
What this one does
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Solves in three directions
Leave spend, conversions or the CPA blank and the tool works out that one.
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Gives the margin ceiling
Contribution per order, which is the most an acquisition can cost before it stops paying for itself.
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Names the overspend
When your CPA is above that ceiling the tool says so, rather than showing a number that looks fine on its own.
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Stays inside media spend
Salaries and tools are not in this figure. Adding them quietly would make the CPA look like a CAC without saying so.
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Carries through to ROAS
With an order value, the same inputs give you the return as well as the cost.
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Checks three entered values
Disagreement of more than one percent gets named instead of resolved for you.
Reading the result
What each line is telling you
- Cost per acquisition
- Media spend per conversion. The number the ad platform is reporting on.
- Contribution per order
- Order value times margin. What one order leaves behind before any advertising.
- Break-even CPA
- The same figure used as a ceiling. Above it, each conversion costs more than it brings.
- ROAS
- Gross return on the spend. Useful for comparison, and not a profit figure.
A free tool answers one question.
A search audit answers the rest.
We look at your search visibility across Google and the answer engines, and tell you what is costing you orders. No charge for the first look.
In practice
What you can do with it
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Set a target before a campaign launches
Work out the ceiling from your margin first. A target CPA set without it is a number somebody hoped for.
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Compare two campaigns fairly
Two campaigns selling different products have different ceilings. The same CPA can be good on one and fatal on the other.
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Turn a target into a budget
Enter the CPA you can afford and the conversions you want, and the spend follows.
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Check a discount before you run it
A discount lowers the margin, which lowers the ceiling. Run the numbers on the discounted margin.
Questions
CPA Calculator questions
What is a good cost per acquisition?
Anything below what one order contributes, which is your order value times your margin. That number is different for every business, which is why an industry average cannot answer this.
Should I count every conversion or only purchases?
Whichever you count, count it consistently. A CPA built on add to carts and compared against a CPA built on purchases describes two different things and looks like a win.
Does CPA include returns?
Not as it is calculated here, because platforms count a conversion at the point of sale. If your return rate is high, the break-even ROAS page handles it properly.
How does target CPA bidding relate to this?
A target CPA you set on a platform is an instruction to the bidder. The number here is what the account did, and the ceiling is what you can afford. Setting the first without knowing the third is common and expensive.
Is my data sent anywhere?
No. Everything is worked out in your browser, with no account and nothing uploaded.
The rest of the set
Fifteen more, all free, all in the browser
- CPM Calculator Work out what a thousand impressions costs, or what a budget buys at a given CPM.
- CTR Calculator Clickthrough rate from clicks and impressions, or the impressions a target needs.
- Conversion Rate Calculator Conversion rate from visitors and conversions, with revenue per visitor beside it.
- ROAS Calculator Return on ad spend, the ACoS behind it, and whether your margin leaves any profit.
- CPC Calculator What one click costs, and what it costs by the time it becomes an order.
- CAC Calculator What winning a customer really costs, including the parts a platform cannot see.
- ARR Calculator Annual recurring revenue, with the net new figure that shows the direction.
- AOV Calculator Average order value, and what a target is worth against the same order count.
- Cost Per Lead Calculator What an enquiry costs, and what it costs once the unqualified half is priced in.
- llms.txt Generator Build an llms.txt file that tells AI crawlers which pages on your store matter.
- LTV Calculator Work out what a customer is worth over time, so you know what you can pay to win one.
- Schema Markup Generator Generate the JSON-LD a product, article or FAQ page needs, ready to paste.
- Break-even ROAS Find the return on ad spend where a campaign stops costing you money.
- CRO ROI Calculator See what a conversion rate change is worth against the traffic you already have.
- Hreflang Generator Produce the hreflang tags a multi-country store needs, without the usual mistakes.
Cost per acquisition only means something next to what an acquisition is worth. On its own it is a number you can always make smaller by buying less of everything.
Where this comes up