# Do I Understand Prometheus's Rate Vs Increase Functions Correctly?

Understanding the `rate` and `increase` functions in Prometheus is crucial for accurately analyzing time-series data. Here's a detailed breakdown of both functions and their differences to ensure you have a solid grasp of how they work.

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### Rate Function

- **Definition**: The `rate` function calculates the average per-second rate of increase of a counter over a specified time range.
- **Usage**: It is primarily used for counters, which are metrics that only increase (or reset). The function is written as:
    
    ```
    rate(metric_name[time_range])
    ```
    
- **Example**: If you have a counter that tracks the number of HTTP requests, you could use:
    
    ```
    rate(http_requests_total[5m])
    ```
    
    This returns the average number of requests per second over the last 5 minutes.
    
- **Key Points**:
    - The result is a rate (requests per second) based on the specified time interval.
    - It handles counter resets automatically (e.g., when the service restarts).
    - Useful for generating smooth graphs over time.

### Increase Function

- **Definition**: The `increase` function calculates the total increase in a counter over a specified time range.
- **Usage**: This function also works with counters, and it’s written as:
    
    ```
    increase(metric_name[time_range])
    ```
    
- **Example**: Continuing with the HTTP request example, you could use:
    
    ```
    increase(http_requests_total[5m])
    ```
    
    This returns the total number of requests that occurred over the last 5 minutes.
    
- **Key Points**:
    - The result is an absolute count of the metric increase over the specified time.
    - It also handles counter resets automatically.
    - Useful for calculating total occurrences (e.g., total requests) over a defined period.

### Key Differences

- **Output**:
    - `rate`: Returns the per-second rate of increase (e.g., requests/second).
    - `increase`: Returns the total increase over the specified time (e.g., total requests).
- **Use Cases**:
    - Use `rate` when you are interested in the speed of change or performance (e.g., how fast requests are coming in).
    - Use `increase` when you need to know the total amount of something that occurred (e.g., total requests over a time period).


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