> ## 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.

# Unique Customers: Distinct Buyers in Period

> Track the number of distinct customers who placed orders in your selected period. Understand buyer count independently of order volume.

<Tip>
  The count of distinct customers who placed at least one order in the period.
</Tip>

## Formula

<Info>
  **Unique Customers** = **COUNT DISTINCT** ( Customer ID ) **WHERE** order placed in period
</Info>

### Formula Components

| Metric          | Definition                                       |
| --------------- | ------------------------------------------------ |
| **Customer ID** | Unique identifier for each customer from Shopify |

| Metadata        |                             |
| --------------- | --------------------------- |
| **Type**        | Number                      |
| **Data Source** | [Shopify](/sources/shopify) |
| **Aggregation** | Count Distinct              |

***

## Example

Your store served **2,847 unique customers** in February:

| Week   | Unique Customers | Orders | Avg Orders/Customer |
| ------ | ---------------- | ------ | ------------------- |
| Week 1 | 712              | 892    | 1.25                |
| Week 2 | 684              | 821    | 1.20                |
| Week 3 | 756              | 934    | 1.24                |
| Week 4 | 695              | 847    | 1.22                |

The monthly unique customers (2,847) is less than the sum of weekly counts because some customers purchased in multiple weeks.

***

## How It Works

Each customer is counted once regardless of how many orders they placed. A customer who placed 5 orders counts the same as one who placed 1 order. This metric uses Shopify customer identifiers to deduplicate across the selected time period.

***

## When to Use

| Scenario                    | Action                                         |
| --------------------------- | ---------------------------------------------- |
| Measuring acquisition reach | Track unique buyers separate from order volume |
| Calculating repeat rate     | Compare unique customers to total orders       |
| Sizing customer base        | Understand how many people you served          |
| Cohort analysis             | Track unique customers by acquisition period   |

***

## Related Metrics

| Metric                                                                                     | Relationship                                    |
| ------------------------------------------------------------------------------------------ | ----------------------------------------------- |
| [New Customers](/reference/metrics/orders/customers/new-customers)                         | First-time buyers subset                        |
| [Returning Customers](/reference/metrics/orders/customers/returning-customers)             | Repeat buyers subset                            |
| [Orders](/reference/metrics/orders/counts/orders)                                          | Total order count (may exceed unique customers) |
| [Avg Orders Per Customer](/reference/metrics/orders/customers/average-orders-per-customer) | Orders ÷ Unique Customers                       |

[See all Customers metrics →](/reference/metrics/orders/customers)