> ## 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 Subscribe: Measure Subscriber Acquisition Efficiency

> Calculate cost per subscribe event to measure how efficiently your ad spend acquires newsletter subscribers. Track subscriber acquisition efficiency with formula and tips.

<Tip>
  Average ad spend per subscribe event tracked by the Upstack pixel.
</Tip>

## Formula

<Info>
  **Cost per Subscribe** = [**Channel Spend**](/reference/metrics/advertising/blended/blended-spend) ÷ [**Subscribes**](/reference/metrics/funnel/conversions/subscribe)
</Info>

### Formula Components

| Metric                                                                    | Definition                                                               |
| ------------------------------------------------------------------------- | ------------------------------------------------------------------------ |
| [**Channel Spend**](/reference/metrics/advertising/blended/blended-spend) | Total advertising spend across connected ad platforms                    |
| [**Subscribes**](/reference/metrics/funnel/conversions/subscribe)         | Total subscribe events (newsletter signups) tracked by the Upstack pixel |

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

***

## Example

Your store spent **\$3,000** on ads last week and generated **1,200 newsletter subscriptions**:

| Channel   | Spend       | Subscribes | Cost per Subscribe |
| --------- | ----------- | ---------- | ------------------ |
| Meta      | \$2,000     | 800        | \$2.50             |
| Google    | \$700       | 280        | \$2.50             |
| TikTok    | \$300       | 120        | \$2.50             |
| **Total** | **\$3,000** | **1,200**  | **\$2.50**         |

***

## How It Works

Cost per Subscribe divides your total advertising spend by the number of subscribe events captured by the Upstack pixel. These events fire when visitors sign up for newsletters, mailing lists, or SMS subscriptions. Lower values indicate more efficient subscriber acquisition—you're paying less for each new email or SMS contact.

***

## When to Use

| Scenario                       | Action                                                                |
| ------------------------------ | --------------------------------------------------------------------- |
| Email list growth budgeting    | Estimate spend needed to hit subscriber acquisition targets           |
| Channel efficiency comparison  | Identify which platforms acquire subscribers most cost-effectively    |
| Lead nurturing funnel analysis | Compare subscriber acquisition cost against eventual conversion value |
| Campaign optimization          | Reallocate budget toward channels with lower cost per subscribe       |

***

## Related Metrics

| Metric                                                                   | Relationship                                        |
| ------------------------------------------------------------------------ | --------------------------------------------------- |
| [Subscribe](/reference/metrics/funnel/conversions/subscribe)             | Denominator—total subscriber count                  |
| [Subscribe Value](/reference/metrics/funnel/conversions/subscribe-value) | Total monetary value attributed to subscribe events |
| [Cost per Lead](/reference/metrics/funnel/conversions/cost-per-lead)     | Similar efficiency metric for lead form submissions |

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