What is Cost Per Acquisition?
Cost per acquisition is total ad spend divided by the conversions that spend produced. It's the metric automated bidding optimises against, the one you compare to gross profit per order, and the one that tells you whether a campaign should scale or stop. CPA differs from CAC in scope: CPA is usually media-only and campaign-level, while CAC is fully loaded with salaries and tools across the whole business.
Why it matters
- It's directly comparable to your gross profit per order. If CPA exceeds it, the campaign loses money on every sale no matter how good the other metrics look.
- Target CPA bidding needs an accurate CPA to work against — feed it a target based on revenue rather than profit and the algorithm will faithfully scale unprofitable volume.
- It's the cleanest way to compare campaigns with very different CPCs and conversion rates, because it collapses both into one outcome.
The formula
CPA = (Total Ad Spend + Other Campaign Costs) ÷ Conversions
- Total Ad Spend
- — media spend for the campaign over the period
- Conversions
- — completed conversions attributed to that spend in the same window
- Other Campaign Costs
- — optional — agency, creative and tooling costs; 0 gives the platform-only figure
How to use this calculator
- 01Pick one campaign and one attribution window, and keep both constant when you compare periods.
- 02Enter the media spend and the conversions it produced.
- 03Compare the result to your gross profit per conversion — not your revenue per conversion. That comparison is the whole decision.
- 04If CPA is above your profit per order, check conversion rate and CPC separately to see which side of the equation is the problem.
Worked example
An ecommerce brand spent $12,000 on a Meta campaign that produced 96 purchases.
- Total spend = $12,000
- Conversions = 96
- CPA = $12,000 ÷ 96 = $125
With a $210 average order value at 55% gross margin, gross profit per order is about $115 — so a $125 CPA is losing roughly $10 on every sale before overheads. Volume won't fix that; margin or conversion rate has to.
Industry benchmarks
Compiled August 2026
Ecommerce (mid-ticket)
$25 – $90
Must sit below gross profit per order to work.
Mobile app install → paying user
$40 – $150
Install CPA is far lower; paying-user CPA is the real number.
B2B SaaS trial signup
$80 – $300
Trial CPA, not customer CPA — apply your trial-to-paid rate.
Subscription box / DTC
$30 – $110
Judged against first-order value plus expected repeat purchases.
Common mistakes
- Comparing CPA to average order value instead of gross profit per order, which makes losing campaigns look profitable.
- Changing the attribution window mid-analysis — a 7-day click window and a 1-day window produce very different CPAs from identical spend.
- Counting platform-reported conversions across channels and double-counting the same sale in two dashboards.
- Judging CPA on too few conversions; below roughly 30 conversions the number swings wildly week to week.
How to improve your CPA
Work the conversion rate side, not just the cost side
CPA equals CPC divided by conversion rate. Doubling conversion rate halves CPA just as surely as halving CPC does, and it's usually the cheaper of the two to move.
Check your conversion rate →Set your target CPA from margin, then let bidding chase it
Automated bidding is good at hitting a target and indifferent to whether the target is profitable. Derive it from gross profit before you enter it.
Find your break-even ROAS →Cut the tail before scaling the head
In most accounts a minority of ad sets carry a majority of the wasted spend. Removing them lowers blended CPA immediately, with no creative work.
Frequently asked questions
What's the difference between CPA and CAC?+
CPA is usually campaign-level and media-only. CAC is business-level and fully loaded — it includes salaries, tools, agency fees, and every channel, including the ones with no media cost at all. CAC is always the higher and more honest number.
What CPA should I target?+
Start from gross profit per conversion and subtract the margin you need. If an order yields $115 in gross profit and you want a 30% contribution margin, your target CPA is around $80 — not $115.
Why does my platform CPA look better than my real CPA?+
Ad platforms claim conversions they influenced under their own attribution model, and several platforms will claim the same sale. Reconciling against actual orders in your own system almost always produces a higher, truer CPA.
Is a rising CPA always bad?+
Not necessarily. Scaling into broader audiences raises CPA by design; if the extra volume is still above break-even, a higher CPA with more total profit is the better outcome.
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