How to Calculate Cost Per Acquisition (CPA): Formula and Examples

The cost per acquisition formula

Cost per acquisition (CPA) measures how much you pay, on average, to win one conversion. The formula is a single division:

CPA = Total ad spend ÷ Number of conversions

A "conversion" is whatever outcome you count as a win — a purchase, a lead, a sign-up, a free trial, or an app install. The only rule is to define it consistently and to align the spend window with the conversion window, so the dollars and the outcomes cover the same period. CPA is the most universal efficiency metric in paid media because it ties spend directly to results rather than to clicks or impressions.

A worked example

Suppose you spent $5,000 on a Google Ads campaign last month and it produced 200 conversions. Your CPA is:

$5,000 ÷ 200 = $25.00 per acquisition

Now compare two channels running the same month. Channel A spends $5,000 for 200 conversions (a $25 CPA). Channel B spends $5,000 for 60 conversions (an $83 CPA). Same budget, very different efficiency — and CPA is the number that makes the gap obvious. Whether an $83 CPA is actually a problem depends on what each customer is worth, which is why CPA is always read next to average order value or lifetime value. The CPA calculator runs this division in one click.

CPA benchmarks by industry in 2026

What counts as a healthy CPA depends entirely on customer value, but industry averages give you a reference point. Across all industries, the average cost per acquisition on Google Search rose 6% year over year to $53.89 in 2026, with display campaigns averaging $61.01, according to DigitalApplied's 2026 benchmarks. High-value, long-cycle categories carry the highest CPAs because each customer is worth far more:

For lead-generation campaigns specifically, LocaliQ's 2026 search benchmarks put the average cost per lead at $66.69, at an 8.18% conversion rate — a useful cross-check when your conversions are leads rather than sales.

CPA vs CAC: don't confuse them

Cost per acquisition and customer acquisition cost (CAC) sound identical but answer different questions. CPA usually measures the cost of a single conversion on one channel — a lead or a sale from a specific campaign. CAC is the fully loaded, blended cost of a paying customer across every channel, plus salaries, tools and agency fees.

• CPA — narrow and channel-level. Total ad spend ÷ conversions. Best for optimizing individual campaigns.
• CAC — broad and company-level. Total sales & marketing cost ÷ new customers. Best for judging whether growth is sustainable.

A campaign can post a tidy $25 CPA while your true CAC is $200 once you fold in salaries and software. Track both: CPA to tune media, CAC (against lifetime value) to size the business.

How to lower your CPA

Because CPA is downstream of both cost per click and conversion rate, the fastest lever is usually the landing page, not the bid. Raising conversion rate lowers CPA even if your CPC stays flat: doubling conversion rate from 2% to 4% halves your CPA on the same traffic.

• Improve conversion rate — message-match between ad and landing page, less form friction, faster pages, clearer trust signals.
• Tighten targeting — bid toward higher-intent audiences and keywords so fewer clicks are wasted.
• Refine creative — better ads lift click-through and quality, which lowers cost per click.
• Use conversion-goal bidding — let smart bidding optimize toward acquisitions rather than clicks.

Measure before and after every change with the CPA calculator, and always confirm a lower CPA hasn't come at the cost of fewer or lower-value conversions.