> ## 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 Trial Extended: Extension Acquisition Cost

> Calculate cost per trial extension to measure retention investment. Track spend associated with extended trial periods.

<Tip>
  Cost per Trial Extended measures the average advertising spend associated with users who received trial extensions.
</Tip>

## Formula

<Info>
  **Cost per Trial Extended** = **Channel Spend** ÷ **Trial Extended**
</Info>

### Formula Components

| Metric                                                                     | Definition                                  |
| -------------------------------------------------------------------------- | ------------------------------------------- |
| [**Channel Spend**](/reference/metrics/advertising/blended/blended-spend)  | Total advertising spend across all channels |
| [**Trial Extended**](/reference/metrics/funnel/conversions/trial-extended) | Count of trial extension events             |

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

***

## Example

Your SaaS company spent **\$25,500** on acquisition in August, resulting in **340 trial extensions**.

| Acquisition Channel | Spend        | Extensions | Cost/Extension |
| ------------------- | ------------ | ---------- | -------------- |
| Google Ads          | \$10,000     | 120        | \$83.33        |
| Meta                | \$8,000      | 110        | \$72.73        |
| LinkedIn            | \$5,000      | 70         | \$71.43        |
| Referrals           | \$2,500      | 40         | \$62.50        |
| **Total**           | **\$25,500** | **340**    | **\$75.00**    |

***

## How It Works

The metric divides total advertising spend by the number of trial extension events. This helps understand the acquisition cost for users who needed more evaluation time. Combined with extension conversion rates, it reveals the true cost of nurturing hesitant prospects.

***

## When to Use

| Scenario                 | Action                                     |
| ------------------------ | ------------------------------------------ |
| Evaluate extension ROI   | Compare cost to conversion value           |
| Identify channel quality | High extension rates may indicate poor fit |
| Budget retention efforts | Understand cost of extended evaluation     |
| Optimize trial duration  | Compare against standard trial costs       |

***

## Related Metrics

| Metric                                                                             | Relationship                        |
| ---------------------------------------------------------------------------------- | ----------------------------------- |
| [Trial Extended](/reference/metrics/funnel/conversions/trial-extended)             | The denominator in this calculation |
| [Trial Extended Value](/reference/metrics/funnel/conversions/trial-extended-value) | Revenue to compare against cost     |
| [Cost per Trial Started](/reference/metrics/funnel/conversions/trial-started-cost) | Standard trial acquisition cost     |

[See all Funnel Conversion metrics →](/reference/metrics/funnel/conversions)