> ## Documentation Index
> Fetch the complete documentation index at: https://docs.upstackdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Cost per Repeat Purchase: Returning Customer Acquisition Cost

> Track cost per repeat purchase for your Shopify store. Measure advertising efficiency in converting returning customers and optimize retention spend.

<Tip>
  Cost per Repeat Purchase measures how much ad spend is required to generate one purchase from a returning customer.
</Tip>

## Formula

<Info>
  **Cost per Repeat Purchase** = **Channel Spend** ÷ **Repeat Purchase Events**
</Info>

### Formula Components

| Metric                                                                        | Definition                                                                  |
| ----------------------------------------------------------------------------- | --------------------------------------------------------------------------- |
| [**Channel Spend**](/reference/metrics/advertising/blended/blended-spend)     | Total advertising spend across all connected ad platforms                   |
| [**Repeat Purchases**](/reference/metrics/funnel/conversions/repeat-purchase) | Total purchase events from returning customers tracked by the Upstack Pixel |

| Metadata        |                         |
| --------------- | ----------------------- |
| **Type**        | Currency                |
| **Data Source** | [Upstack Pixel](/pixel) |
| **Aggregation** | Ratio                   |

***

## Example

Your Shopify store spent **\$15,000** on ads last month and tracked **750** repeat purchases from returning customers.

| Metric                       | Value       | Calculation               |
| ---------------------------- | ----------- | ------------------------- |
| Channel Spend                | \$15,000    | Total ad spend            |
| Repeat Purchases             | 750         | Returning customer orders |
| **Cost per Repeat Purchase** | **\$20.00** | \$15,000 ÷ 750            |

***

## How It Works

The Upstack Pixel tracks every purchase event and identifies whether the customer has previously purchased from your Shopify store. Repeat purchases are orders placed by customers who have at least one prior order. This metric divides your total ad spend by the count of repeat purchase events to show your cost efficiency for returning customer conversions.

***

## When to Use

| Scenario                                               | Action                                                                         |
| ------------------------------------------------------ | ------------------------------------------------------------------------------ |
| Comparing new vs. returning customer acquisition costs | Compare against Cost per New Customer Purchase to optimize budget allocation   |
| Evaluating retention campaign efficiency               | Monitor whether retargeting campaigns deliver cost-effective repeat purchases  |
| Budgeting for customer reactivation                    | Use as a baseline for setting CPA targets on win-back campaigns                |
| Analyzing channel performance by customer type         | Break down by channel to find which platforms drive efficient repeat purchases |

***

## Related Metrics

| Metric                                                                                                 | Relationship                                      |
| ------------------------------------------------------------------------------------------------------ | ------------------------------------------------- |
| [Repeat Purchases](/reference/metrics/funnel/conversions/repeat-purchase)                              | The denominator in this calculation               |
| [Cost per New Customer Purchase](/reference/metrics/funnel/conversions/cost-per-new-customer-purchase) | Compare acquisition cost for first-time buyers    |
| [Cost per Purchase](/reference/metrics/funnel/conversions/cost-per-purchase)                           | Overall purchase cost regardless of customer type |
| [Channel Spend](/reference/metrics/advertising/blended/blended-spend)                                  | The numerator in this calculation                 |

[See all Conversions metrics →](/reference/metrics/funnel/conversions)