> ## 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 Lapsed Purchase: Win-Back Acquisition Efficiency

> Track the cost to reactivate lapsed customers for your Shopify store. Calculate Channel Spend divided by Lapsed Purchases to optimize win-back campaigns.

<Tip>
  Cost per Lapsed Purchase measures the average ad spend required to generate one purchase from a lapsed customer, tracked by the Upstack pixel.
</Tip>

## Formula

<Info>
  **Cost per Lapsed Purchase** = **Channel Spend** ÷ **Lapsed Purchases**
</Info>

### Formula Components

| Metric                                                                         | Definition                                                            |
| ------------------------------------------------------------------------------ | --------------------------------------------------------------------- |
| [**Channel Spend**](/reference/metrics/advertising/blended/blended-spend)      | Total amount spent on advertising across all channels                 |
| [**Lapsed Purchases**](/reference/metrics/funnel/conversions/lapsed-purchases) | Purchase events from customers who returned after extended inactivity |

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

***

## Example

Your Shopify store spent **\$8,500** on win-back campaigns in February and reactivated **170 lapsed customers** who completed purchases.

| Metric                       | Value       | Calculation                          |
| ---------------------------- | ----------- | ------------------------------------ |
| Channel Spend                | \$8,500     | Total ad spend on win-back campaigns |
| Lapsed Purchases             | 170         | Reactivated customer conversions     |
| **Cost per Lapsed Purchase** | **\$50.00** | \$8,500 ÷ 170                        |

***

## How It Works

Upstack tracks purchase events from your Shopify store and identifies lapsed customers—those who have been inactive beyond the typical repurchase window. When these dormant customers return and complete a purchase, the event is tracked as a lapsed purchase. This metric divides your total advertising spend by the number of these win-back conversions, showing the true cost to reactivate a churned customer.

***

## When to Use

| Scenario                      | Action                                                                           |
| ----------------------------- | -------------------------------------------------------------------------------- |
| Evaluating win-back campaigns | Compare cost per lapsed purchase against lifetime value of reactivated customers |
| Optimizing reactivation spend | Identify which channels reactivate dormant customers most efficiently            |
| Budget allocation             | Weigh investment in win-back vs. new customer acquisition                        |
| Benchmarking retention costs  | Compare against cost per new customer to assess reactivation ROI                 |

***

## Related Metrics

| Metric                                                                                             | Relationship                                |
| -------------------------------------------------------------------------------------------------- | ------------------------------------------- |
| [Lapsed Purchases](/reference/metrics/funnel/conversions/lapsed-purchases)                         | Denominator in this calculation             |
| [Channel Spend](/reference/metrics/advertising/blended/blended-spend)                              | Numerator in this calculation               |
| [New Customer Purchase Cost](/reference/metrics/funnel/conversions/cost-per-new-customer-purchase) | Compare acquisition vs. win-back efficiency |

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