CPA calculator
Cost per acquisition from your ad spend, with CPC, CPM, click through rate and conversion rate alongside it and the arithmetic shown. Free, nothing stored.
This is the advertising metric, cost per acquisition. If you meant the CPA accountancy qualification or a grade point average, search for those instead.
The total the campaign cost you over the period you are measuring.
Completed actions: sales, leads, signups, downloads. Whichever one you are paying for.
Unlocks cost per click and conversion rate.
Unlocks CPM and click through rate.
Changes the symbol on screen. No conversion happens.
What an average order or customer is worth in revenue.
The share of an order left after the cost of what you sold. With order value, this gives your break even CPA.
A ratio, so 4 means 4 back for every 1 spent. Gives the CPA you would need to hit it.
Revenue attributed to this spend. Gives your ROAS.
Enter your ad spend and any two of impressions, clicks and conversions. Whatever can be worked out from those numbers appears as you type, with the arithmetic underneath, and anything that cannot says which field it still needs. Or .
How to calculate cost per acquisition
- Add up what the campaign cost. Take the total you paid for a single campaign over a single date range, including anything the platform charged on top of the media itself. One range, one campaign, one number. Mixing a month of spend with a quarter of conversions is the most common way a CPA comes out wrong, and nothing in the arithmetic will warn you.
- Count the conversions that spend produced, and decide first what a conversion is. A sale, a qualified lead, a trial signup, an app install and a whitepaper download are all valid actions, and they give wildly different numbers for the same campaign. Write the definition down, use the same date range you used for the cost, and keep both fixed every time you report the figure.
- Divide the cost by the conversions. 12,000 of spend and 240 conversions gives 12,000 / 240 = 50.00, so each conversion cost you 50.00. Then compare that against your own break even CPA rather than against a published average: break even CPA is your average order value times your gross margin, and it is the only number that tells you whether 50.00 is affordable in your business.
How CPA, CPC, CPM and conversion rate fit together
These four get treated as four separate things to look up. They are not. Three of them are the same spend divided by a different denominator, and once you see how they connect you can move between them in your head. Every example below uses one campaign: 12,000 of spend, 400,000 impressions, 6,000 clicks and 240 conversions.
CPA, cost per acquisition
CPA = total campaign cost / conversions
12,000 of spend and 240 conversions gives 12,000 / 240 = 50.00 per conversion.
CPC, cost per click
CPC = cost / clicks
That same 12,000 across 6,000 clicks gives 12,000 / 6,000 = 2.00 per click.
CPM, cost per 1,000 impressions
CPM = (cost / impressions) × 1000
400,000 impressions for 12,000 gives (12,000 / 400,000) × 1000 = 30.00 per thousand impressions. The M is the Roman thousand, not million.
CTR, click through rate
CTR = (clicks / impressions) × 100
6,000 clicks from 400,000 impressions gives (6,000 / 400,000) × 100 = 1.50%.
CVR, conversion rate
CVR = (conversions / clicks) × 100
240 conversions from 6,000 clicks gives (240 / 6,000) × 100 = 4.00%.
The link worth knowing: CPA = CPC / CVR
Start from the definition and substitute twice. Your cost is what you paid per click multiplied by the clicks you bought. Your conversions are those same clicks multiplied by the rate at which they convert. Put both into the CPA formula and the clicks cancel.
- CPA = cost / conversions
- cost = CPC × clicks
- conversions = clicks × CVR (CVR as a decimal)
- CPA = (CPC × clicks) / (clicks × CVR)
- CPA = CPC / CVR
Check it on the campaign above. CPC is 2.00 and the conversion rate is 4.00%, which is 0.04 as a decimal, so 2.00 / 0.04 = 50.00. That is the same 50.00 you get from 12,000 / 240. Two routes, one answer, because they were never two different sums.
The practical use of that identity is diagnosis. If your CPA rises, only two things can have caused it: clicks got more expensive, or fewer of them converted. Splitting the number tells you which, and the two problems have nothing in common. Rising CPC is an auction and targeting problem. A falling conversion rate is a landing page, offer or traffic quality problem. It also shows why buying cheaper clicks can make things worse: halve your CPC by chasing loose traffic, and if the conversion rate falls further than half, your CPA goes up. CTR sits outside that chain entirely, since it says nothing about cost, and CPM is only useful for comparing what it costs to be seen. Neither one tells you what a customer cost.
Three related numbers finish the picture. Break even CPA is the gross profit one customer brings in, which is average order value times gross margin: an 80 order at a 55% margin leaves 44.00, so above a CPA of 44.00 you lose money on every acquisition. Target CPA from a target ROAS is average order value divided by that target, so an 80 order at a 4x target means paying no more than 20.00. And ROAS itself is revenue divided by ad spend, reported as a ratio like 1.60x, never as a percentage, because it never subtracts the spend it divides by.
CPA is not CAC
These two get swapped for each other constantly, including in reporting that budgets are set from. CPA is the cost of one defined action, and you choose the action: a lead, a trial signup, a download, a sale. CAC, customer acquisition cost, normally counts your total sales and marketing cost, media plus salaries plus tools plus agency fees, divided by the number of new customers acquired in the same period. Different numerator, different denominator, different question.
Here is the same business in the same month. It spends 12,000 on ads and gets 240 free trial signups, so its CPA on that action is 12,000 / 240 = 50.00. Of those 240 trials, 60 become paying customers. Its full sales and marketing cost for the month, once the two salaries and the tooling are counted, is 30,000. So its CAC is 30,000 / 60 = 500.00. Both numbers are correct. They are ten times apart, and each one is only correct for its own question.
The damage is in quoting one where the other was meant. Tell an investor your acquisition cost is 50 when it is 500 and every payback and lifetime value figure downstream is wrong by an order of magnitude. Judge a campaign on a 500 CAC when the action it was buying cost 50 and you will switch off something that was working. This calculator gives you CPA. When someone asks for CAC, take your total sales and marketing cost and divide it by new customers, and say which one you are quoting.
Frequently asked questions
What is a good CPA?
There is no universal number, and any figure quoted without your margin in it is guessing on your behalf. The only benchmark that means anything is your own break even CPA, which is your average order value times your gross margin, because that is the gross profit one customer actually brings in. Sell an average order of 80 at a 55% gross margin and each customer leaves you 44.00 before any advertising. That is your ceiling. A CPA of 30.00 makes you money on every acquisition, a CPA of 50.00 loses you 6.00 on every one, and both of those are true regardless of what any industry average says. I do not publish an average CPA by industry table here, because the ones in circulation do not disclose how they were measured, and a benchmark you cannot check is not a benchmark. The break even calculation is arithmetic you can verify in a minute.
What is the difference between CPA and CPC?
CPC is what you pay for a click, and CPA is what you pay for a completed action, so CPA is always the larger of the two unless every single click converts. The bridge between them is your conversion rate: CPA = CPC / CVR. At 2.00 a click and a 4% conversion rate, you are paying 50.00 per conversion, because it takes 25 clicks on average to get one. Cheaper clicks only help if the conversion rate holds, which is why chasing CPC on its own so often moves CPA the wrong way.
Why is my CPA undefined?
Because you have no conversions yet, and cost per acquisition is spend divided by conversions. Dividing by zero has no answer. It is not zero, since you have clearly spent money, and it is not infinite either, since infinity is not a cost you could pay. I show the sentence instead of a number, because a calculator that prints Infinity or 0.00 there is telling you something false. The moment one conversion lands, your CPA is your whole spend divided by that one conversion, and it falls from there.
Is CPA the same as CAC?
No, and treating them as synonyms is the most expensive mistake on this page. CPA is the cost of one defined action, whatever you chose that action to be: a lead, a signup, a download or a sale. CAC, customer acquisition cost, normally counts your total sales and marketing cost, including salaries, tools and agency fees, divided by the number of new customers acquired in the same period. The two answer different questions, and in the worked example on this page the same business in the same month has a CPA of 50.00 and a CAC of 500.00. If you quote your CPA where a CAC was meant, your payback period and your budget will both be wrong.
Do you store my numbers?
No. The maths runs in your browser, nothing is sent to a server, and nothing is saved. Refresh the page and it is gone. Use the copy button if you want to keep a result.