> ## 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 MER (Gross Sales): Retention Gross Efficiency

> Track returning customer marketing efficiency using gross sales. Understand what percentage of repeat buyer gross revenue is spent on ads.

<Tip>
  Returning Customer MER (Gross) measures what percentage of your returning customer gross sales (before discounts and refunds) is spent on advertising.
</Tip>

## Formula

<Info>
  **RC MER (Gross)** = ( **Total Ad Spend** ÷ **RC Gross Order Sales** ) × 100
</Info>

### Formula Components

| Metric                                                                                     | Definition                                                          |
| ------------------------------------------------------------------------------------------ | ------------------------------------------------------------------- |
| **Total Ad Spend**                                                                         | Combined advertising spend across all connected platforms           |
| [**RC Gross Revenue**](/reference/metrics/orders/revenue/returning-customer-gross-revenue) | Gross order sales from returning customers before discounts/refunds |

| Metadata        |                                                                                                   |
| --------------- | ------------------------------------------------------------------------------------------------- |
| **Type**        | Percentage                                                                                        |
| **Data Source** | [Shopify](/sources/shopify), [Meta Ads](/sources/facebook-ads), [Google Ads](/sources/google-ads) |
| **Aggregation** | Ratio                                                                                             |

***

## Example

Your Shopify store generated **\$130,000** in returning customer gross sales while spending **\$40,000** on advertising.

| Metric         | Value     | Calculation                  |
| -------------- | --------- | ---------------------------- |
| Total Ad Spend | \$40,000  | All ad platforms             |
| RC Gross Sales | \$130,000 | Before discounts/refunds     |
| RC MER (Gross) | 30.8%     | (\$40,000 ÷ \$130,000) × 100 |

A RC Gross MER of 30.8% means you spend \$0.31 on advertising for every \$1 of returning customer gross sales.

***

## How It Works

RC Gross MER uses returning customer gross sales as the revenue base, excluding the impact of loyalty discounts or refunds. This helps you understand retention efficiency before repeat customer promotions are applied.

***

## When to Use

| Scenario                          | Action                                          |
| --------------------------------- | ----------------------------------------------- |
| Loyalty discount analysis         | See MER before loyalty promo impact             |
| Retention campaign comparison     | Normalize for different discount strategies     |
| Isolating remarketing performance | Remove promo noise from RC efficiency           |
| Pre-discount retention cost       | Understand true cost relative to intended spend |

***

## Related Metrics

| Metric                                                                                 | Relationship                             |
| -------------------------------------------------------------------------------------- | ---------------------------------------- |
| [RC MER](/reference/metrics/orders/performance/returning-customer-total-mer)           | RC MER using total revenue               |
| [RC MER (Net)](/reference/metrics/orders/performance/returning-customer-net-mer)       | RC MER using net revenue after discounts |
| [MER (Gross)](/reference/metrics/orders/performance/gross-mer)                         | Gross MER for all customers              |
| [RC Gross Revenue](/reference/metrics/orders/revenue/returning-customer-gross-revenue) | The denominator in this calculation      |

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