To calculate CPA, divide your ad spend by the conversions it bought over the same dates. $4,800 of spend and 96 purchases is a $50 cost per acquisition. Add your clicks and the calculator also shows your conversion rate; add a target CPA and it shows the conversion rate that target needs.
The first card shows what each conversion cost. Add clicks for your conversion rate, and a target CPA for the rate that target needs.
[ What you get ]
Your cost per acquisition, and the conversion rate behind it
Cost per acquisition decides whether a campaign can take more budget. This page does that one division next to the figures you are weighing, and updates as you type.
What comes out:
- Cost per acquisition. Ad spend divided by conversions, recalculated as you type.
- The conversion rate behind it. Add your clicks and a card shows the rate you convert at. CPA is your cost per click divided by that rate.
- The rate a target needs. Type the CPA you are aiming for, and a card shows the conversion rate it takes at this spend and these clicks, next to the rate you have now.
This is the ad-platform CPA: the spend your account recorded, divided by the conversions it counted. It is not your customer acquisition cost. The page divides the two figures you type, so the answer is only as good as the conversions your ad platform reports.
[ How to use it ]
CPA calculator: three steps
Enter your ad spend
Type what the campaign spent over the dates you care about. You can paste it from Ads Manager: 4,800 and $4,800.00 read the same.
Enter the conversions
Type the purchases, leads or sign-ups that spend bought over the same dates. Whatever your account counts as a conversion is what the CPA means.
Add clicks or a target
Clicks add your conversion rate. A target CPA adds the rate you would need. Leave both empty for the cost per acquisition alone.
Use the same dates for both numbers. Spend from 30 days divided by conversions from 7 gives a CPA about four times too high.
[ Limits ]
Free version limits
The calculator runs in your browser; there is no limit and no account. We don’t store your numbers.
[ The formula ]
CPA formula: ad spend divided by conversions
CPA = ad spend ÷ conversions. A campaign that spent $4,800 and got 96 purchases paid $50 in ad spend for each one. Spend is what the account was charged; a conversion is whatever event the account optimizes for.
Through clicks, CPA is cost per click divided by conversion rate. You don’t control auction prices, but you do control the conversion rate, through the copy, the offer and the page. Lift it from 3% to 4% on the same spend and clicks, and every customer costs a quarter less.
A worked example: $4,800 on Meta over 30 days
| Figure | Working | Result |
|---|---|---|
| Ad spend | What the account was charged over the window | $4,800 |
| Conversions | Purchases the account attributed to those ads | 96 orders |
| Cost per acquisition | 4,800 ÷ 96 | $50.00 |
| Link clicks | Clicks over the same 30 days | 3,200 |
| Conversion rate | 96 ÷ 3,200 | 3.0% |
| Cost per click | 4,800 ÷ 3,200 | $1.50 |
Same $4,800, same 3,200 clicks
| Conversion rate | Conversions | Cost per acquisition |
|---|---|---|
| 2.0% | 64 | $75.00 |
| 3.0% | 96 | $50.00 |
| 4.0% | 128 | $37.50 |
| 5.0% | 160 | $30.00 |
[ Definitions ]
CPA, CPL and CAC are three different numbers
CPA is an ad-platform metric: one campaign, one date range, one conversion event. CAC is a business metric: everything sales and marketing cost, divided by the customers you won. CPL is CPA with a lead as the conversion, so a $50 CPL at a 30% close rate is a $167 cost per customer.
What each one counts
| Metric | What it counts | Where the number comes from |
|---|---|---|
| CPA — cost per acquisition | Ad spend divided by the conversions the platform attributed to it | Ads Manager, or the calculator above |
| CPL — cost per lead | The same division, where the conversion event is a lead rather than a sale | Ads Manager, with a lead set as the optimization event |
| CAC — customer acquisition cost | Everything sales and marketing cost, divided by the new customers won | Your own accounts: media, salaries, tools, agency fees, discounts |
[ Setting a target ]
A good CPA comes out of your margin, not out of a competitor
A good CPA is one your margin can pay for. An $80 average order at a 60% gross margin leaves $48, so $48 is the ceiling if a buyer orders once. If the average customer orders 1.8 times a year, the same margin is worth about $86, and a $60 CPA pays back from the second order.
A competitor’s CPA is no use as a target: you can’t see their margin, their repeat rate or how long they can wait for payback. Put your own ceiling in the Target CPA field. If the rate it needs is far from yours, fix the offer and the landing page, not the bid.
[ Why marketers use it ]
Know the conversion rate your target needs — before you raise the budget
Before a budget goes up, the target field shows whether the campaign can get there. A media buyer enters the CPA the business can afford and reads the conversion rate it takes. The gap to the current rate says whether next week’s work goes into the bid or the landing page.
A founder runs it before launch: the margin sets the ceiling, and the question becomes what conversion rate paid traffic has to reach. An agency uses the same gap when a client’s CPA climbs: the cost per click held, the rate slipped, and here is the rate that brings the target back.
What your own numbers can’t show is why a competitor clears a ceiling you can’t. That answer sits in their ads, in the angles they have kept running for months.
[ Go further with Spytrend ]
The angles your competitors keep funding, beside your CPA ceiling
Your CPA ceiling says what a customer may cost; the ads your competitors keep running show which promises win customers at that price.
Spytrend is an ad intelligence platform for Facebook and TikTok advertising: a full five-year archive of ads, AI-classified into 33 business categories, with every advertiser assembled into a single card — all ads, pages, domains and countries in one place.
Two jobs where one CPA is not enough
- Finding a better conversion rate. When the target needs a rate you don’t have, the gap usually sits before the click: the promise, the offer, the audience. Filter a competitor’s ads to those that have run 60 days or more, and study the promises they kept funding before you rewrite your page.
- Sizing a market before launch. Before launch there is no spend to divide. Search the brands you would compete with and see how long their ads run: months suggest someone makes the numbers work; weeks are a warning.
From one CPA to the ads that clear it, in three steps
- Search your market. Type a competitor’s brand or domain into the ads search.
- Keep the long runs. Set the days filter to 60 or more: what stays is what advertisers kept funding for two months.
- Test the angle here. Build on the angle that fits your margin, then put the new conversion rate back into this calculator.
How to start
Create a free account and search a brand or a domain you compete with. A free account opens the ad library; paid plans add fresh ads and every filter.