CPA Calculator

What is cost per acquisition (CPA)?

Cost per acquisition — CPA, sometimes called cost per action — is the average amount you pay in ad spend for each conversion. A conversion is simply any action you count as a win: a sale, a signup, a lead, a download. So CPA answers a very practical question: how much does it cost me, on average, to get one?

It's one of the clearest ways to judge whether ads are working, because it ties your spend directly to results rather than to clicks or views. Two campaigns can have the same cost per click and wildly different CPAs — and the one with the lower CPA is the one actually turning clicks into outcomes.

How to calculate CPA: the cost-per-acquisition formula

To calculate cost per acquisition, divide your total ad spend by the number of conversions it produced:

CPA = Ad spend ÷ Conversions

For example, $5,000 of ad spend that brings 250 conversions gives a CPA of $20. Because the formula links three values, you can rearrange it to solve for whichever one you're missing — which is what the calculator above does:

• Find CPA — Spend ÷ Conversions ($5,000 ÷ 250 = $20)
• Find Spend — CPA × Conversions ($20 × 250 = $5,000)
• Find Conversions — Spend ÷ CPA ($8,000 ÷ $25 = 320)

A worked example

If you spend $5,000 on a campaign and it drives 250 signups, your cost per acquisition is:

$20 = $5,000 ÷ 250

Each signup cost $20. If you improved the landing page and the same $5,000 now brought 320 signups, the calculator would show your CPA falling to about $15.60 — a quick way to see how much a better conversion rate is worth.

How to use this calculator

1. Choose which value to solve for — CPA, ad spend, or conversions.
2. Enter the two values you already know. Results update instantly as you type.
3. Switch currency if you're planning in something other than dollars.
4. Use Copy shareable link to send the exact scenario to a colleague — the numbers are saved in the URL.

CPA vs CAC — they're not the same

CPA and CAC (customer acquisition cost) sound alike but measure different things:

• CPA is campaign-level — ad spend ÷ conversions, where a conversion is any tracked action. It's what one action costs inside your ad account.
• CAC is business-level — it counts every sales and marketing cost (salaries, tools, agencies), not just ad spend, and divides by new paying customers.

Because CAC includes far more than media cost, it's almost always higher than CPA. Use CPA to optimise individual campaigns, and CAC to check whether the business acquires customers profitably overall.

CPA vs CPL and other cost metrics

CPA is the umbrella term; the others are just CPA measured on a specific action:

• CPL (cost per lead) — a CPA where the action counted is a lead.
• CPI (cost per install) — a CPA where the action is an app install.
• CPC (cost per click) — earlier in the funnel; you pay per click, not per conversion. CPA = CPC ÷ conversion rate.

That last link matters: if clicks cost $1 and 5% of them convert, your CPA is $1 ÷ 0.05 = $20. So a better click-through rate or conversion rate pulls CPA down without touching your bids.

How to judge — and reduce — your CPA

A good CPA is one comfortably below what a conversion is worth to you. A $20 CPA is a bargain if each customer earns you $80, and a disaster if they earn $25 — so always read CPA against the value of a conversion, not a benchmark. For how to weigh acquisition cost against what a customer is worth over time, see what is a good CAC? — the same logic applies to CPA. To bring it down:

• Raise your conversion rate — a faster, clearer landing page turns more of the clicks you already pay for into conversions.
• Tighten targeting so you're paying to reach people the offer actually fits.
• Improve ad relevance to lower your cost per click, which flows straight through to CPA.
• Cut what doesn't convert — pause the keywords, audiences and placements that spend without producing conversions.

Model it all before you spend with the Campaign Forecast, which projects CPA alongside profit and ROAS.