> ## 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.

# Subscription Initial Purchase CPA: Cost Per Subscription Acquisition

> Track cost per subscription initial purchase for your Shopify store. Optimize ad spend efficiency for subscription-based customer acquisition.

<Tip>
  The cost to acquire a subscription initial purchase order, calculated as ad spend divided by subscription initial purchase orders.
</Tip>

## Formula

<Info>
  **Subscription Initial Purchase CPA** = **Spend** ÷ [**Subscription Initial Purchase Orders**](/reference/metrics/orders/counts/subscription-initial-purchase-orders)
</Info>

### Formula Components

| Metric                                                                                                            | Definition                                                             |
| ----------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------- |
| **Spend**                                                                                                         | Total advertising spend for the selected period and attribution window |
| [**Subscription Initial Purchase Orders**](/reference/metrics/orders/counts/subscription-initial-purchase-orders) | Number of attributed orders that were subscription initial purchases   |

| Metadata        |                                                              |
| --------------- | ------------------------------------------------------------ |
| **Type**        | Currency                                                     |
| **Data Source** | [Upstack Pixel](/pixel), [Shopify](/sources/catalog/shopify) |
| **Aggregation** | Ratio                                                        |

***

## Example

Subscription acquisition costs across different ad campaigns:

| Campaign          | Ad Spend | Initial Sub. Purchases | CPA     |
| ----------------- | -------- | ---------------------- | ------- |
| Meta Subscription | \$5,000  | 125                    | \$40.00 |
| Google Search     | \$3,200  | 64                     | \$50.00 |
| TikTok            | \$2,500  | 42                     | \$59.52 |

***

## How It Works

Subscription Initial Purchase CPA measures how efficiently your advertising drives subscription sign-ups. It only counts orders identified as subscription initial purchases through matching with subscription\_initial\_purchase events. Lower CPA means more efficient acquisition of recurring customers from your Shopify store.

***

## When to Use

| Scenario                          | Action                                                             |
| --------------------------------- | ------------------------------------------------------------------ |
| Evaluating subscription campaigns | Compare CPA across channels targeting subscriptions                |
| Setting subscription CAC targets  | Use CPA to establish profitable acquisition thresholds             |
| Comparing to one-time CPA         | See premium/discount for acquiring subscribers vs. one-time buyers |
| Forecasting subscription LTV      | Pair with subscription retention for payback analysis              |

***

## Related Metrics

| Metric                                                                                                         | Relationship                                     |
| -------------------------------------------------------------------------------------------------------------- | ------------------------------------------------ |
| [Subscription Initial Purchase ROAS](/reference/metrics/orders/performance/subscription-initial-purchase-roas) | Revenue efficiency for subscription acquisitions |
| [Subscription Initial Purchase Orders](/reference/metrics/orders/counts/subscription-initial-purchase-orders)  | Denominator in this calculation                  |
| [CAC](/reference/metrics/orders/performance/cac)                                                               | Overall customer acquisition cost                |
| [CPA](/reference/metrics/orders/performance/cac)                                                               | General cost per acquisition                     |

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