Google Cost per Purchase: Acquisition Efficiency

Google Cost per Purchase measures how much you spend on average to drive each purchase through your Google Ads campaigns.

Formula

Google Cost per Purchase = Google Spend ÷ Google Purchases

Formula Components

Metric	Definition
Google Spend	Total amount billed by Google for advertising
Google Purchases	Number of purchases attributed to Google ads

Metadata
Type	Currency
Data Source	Google Ads
Aggregation	Ratio

Example

A home decor store spent $4,200 on Google Ads in March and drove 84 purchases.

Metric	Value	Calculation
Google Spend	$4,200	Total ad spend
Google Purchases	84	Attributed conversions
Cost per Purchase	$50.00	$4,200 ÷ 84

How It Works

Google Cost per Purchase divides your total Google Ads spend by the number of purchases attributed to those campaigns. Lower values indicate more efficient acquisition—you’re spending less to acquire each customer through Google.

When to Use

Scenario	Action
High cost per purchase	Pause underperforming campaigns or ad groups
Compare campaign types	Evaluate Search vs Shopping vs Performance Max efficiency
Budget allocation	Shift spend to campaigns with lower acquisition costs
Cross-platform comparison	Compare against Meta or TikTok cost per purchase

Metric	Relationship
Google Spend	Numerator in calculation
Google Purchases	Denominator in calculation
Google ROAS	Revenue-based efficiency metric

See all Google Efficiency metrics →

Google CPA Google All Conv. ROAS

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​Formula

​Formula Components

​Example

​How It Works

​When to Use

​Related Metrics

Formula

Formula Components

Example

How It Works

When to Use

Related Metrics