> ## 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.

# Returning Customer CM3 MER: Repeat Order Contribution Margin Efficiency

> Track returning customer CM3 MER for your Shopify store. Measure contribution margin generated per dollar of ad spend on repeat orders.

<Tip>
  Returning Customer CM3 MER measures how much contribution margin (after all variable costs including ad spend) you generate from repeat orders per dollar of ad spend.
</Tip>

## Formula

<Info>
  **Returning Customer CM3 MER** = **Returning Customer CM3** ÷ **Ad Spend**
</Info>

### Formula Components

| Metric                                                                                                             | Definition                                   |
| ------------------------------------------------------------------------------------------------------------------ | -------------------------------------------- |
| [**Returning Customer CM3**](/reference/metrics/orders/contribution-margin/returning-customer-contribution-margin) | Contribution margin from repeat buyer orders |
| [**Ad Spend**](/reference/metrics/advertising/blended/blended-spend)                                               | Total advertising spend                      |

| Metadata        |                                                                                             |
| --------------- | ------------------------------------------------------------------------------------------- |
| **Type**        | Ratio                                                                                       |
| **Data Source** | [Shopify](/sources/catalog/shopify), [Advertising Platforms](/sources/catalog/facebook-ads) |
| **Aggregation** | Ratio                                                                                       |

***

## Example

Your Shopify store generates **\$33,000** CM3 from returning customers and spends **\$15,000** on ads.

| Component                      | Value    | Calculation                      |
| ------------------------------ | -------- | -------------------------------- |
| Returning Customer CM3         | \$33,000 | Repeat order contribution margin |
| Ad Spend                       | \$15,000 | Marketing cost                   |
| **Returning Customer CM3 MER** | **2.2**  | \$33,000 ÷ \$15,000              |

***

## How It Works

Returning Customer CM3 MER shows contribution margin efficiency for repeat orders. This is typically much higher than new customer CM3 MER because repeat orders don't carry acquisition costs—just their share of ongoing ad spend.

***

## Benchmarks

| Rating     | Range     |
| ---------- | --------- |
| Excellent  | > 2.5     |
| Good       | 1.5 – 2.5 |
| Moderate   | 0.8 – 1.5 |
| Concerning | \< 0.8    |

Strong returning customer CM3 MER indicates healthy repeat purchase contribution.

***

## Related Metrics

| Metric                                                                                                         | Relationship                    |
| -------------------------------------------------------------------------------------------------------------- | ------------------------------- |
| [Returning Customer CM3](/reference/metrics/orders/contribution-margin/returning-customer-contribution-margin) | Numerator (contribution margin) |
| [CM3 MER](/reference/metrics/orders/performance/cm3-mer)                                                       | Overall CM3 efficiency          |
| [New Customer CM3 MER](/reference/metrics/orders/performance/new-customer-cm3-mer)                             | First-order efficiency          |

[See all Performance metrics →](/reference/metrics/orders/performance)