> ## 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 CM2 MER: Repeat Order Variable Margin Efficiency

> Track returning customer CM2 MER for your Shopify store. Measure variable margin generated per dollar of ad spend on repeat orders.

<Tip>
  Returning Customer CM2 MER measures how much variable margin (after COGS and fulfillment) you generate from repeat orders per dollar of ad spend.
</Tip>

## Formula

<Info>
  **Returning Customer CM2 MER** = **Returning Customer CM2** ÷ **Ad Spend**
</Info>

### Formula Components

| Metric                                                                                             | Definition                               |
| -------------------------------------------------------------------------------------------------- | ---------------------------------------- |
| [**Returning Customer CM2**](/reference/metrics/orders/contribution-margin/returning-customer-cm2) | Variable 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 **\$48,000** CM2 from returning customers and spends **\$15,000** on ads.

| Component                      | Value    | Calculation                  |
| ------------------------------ | -------- | ---------------------------- |
| Returning Customer CM2         | \$48,000 | Repeat order variable margin |
| Ad Spend                       | \$15,000 | Marketing cost               |
| **Returning Customer CM2 MER** | **3.2**  | \$48,000 ÷ \$15,000          |

***

## How It Works

Returning Customer CM2 MER shows variable margin efficiency for repeat orders. Since returning customers don't require acquisition costs, this ratio is typically higher than the new customer equivalent.

***

## Benchmarks

| Rating     | Range     |
| ---------- | --------- |
| Excellent  | > 3.5     |
| Good       | 2.0 – 3.5 |
| Moderate   | 1.2 – 2.0 |
| Concerning | \< 1.2    |

Strong returning customer CM2 MER indicates healthy repeat purchase economics.

***

## Related Metrics

| Metric                                                                                         | Relationship                |
| ---------------------------------------------------------------------------------------------- | --------------------------- |
| [Returning Customer CM2](/reference/metrics/orders/contribution-margin/returning-customer-cm2) | Numerator (variable margin) |
| [CM2 MER](/reference/metrics/orders/performance/cm2-mer)                                       | Overall CM2 efficiency      |
| [New Customer CM2 MER](/reference/metrics/orders/performance/new-customer-cm2-mer)             | First-order efficiency      |

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