free - Check Memory Usage Easily

The free command displays the amount of free and used memory in the system. It provides information about RAM and swap usage, as well as buffers and caches used by the kernel.

Syntax

free [OPTIONS]

Description of Output Columns

Column	Description
`total`	Total amount of memory (RAM or swap).
`used`	Memory used. This includes buffers and cache unless `-/+ buffers/cache` is shown.
`free`	Memory not used at all.
`shared`	Memory used (mostly) by tmpfs or shared between processes.
`buff/cache`	Memory used by the kernel buffers and page cache.
`available`	Estimated memory available for starting new applications (Linux ≥ 3.14).

Note: The available memory gives a more accurate idea of how much memory is really available for applications.

Options

Option	Description
`-h`	Human-readable output (e.g., in MB/GB).
`-m`	Show output in megabytes.
`-g`	Show output in gigabytes.
`-s <sec>`	Continuously display every `<sec>` seconds.
`-t`	Show total line.

Practical Examples

1. Basic usage (default in kilobytes)

free

2. Human-readable format (best for general use)

free -h

Example Output:

              total        used        free      shared  buff/cache   available
Mem:           15Gi       4.2Gi       1.1Gi       1.0Gi       9.7Gi       9.7Gi
Swap:         2.0Gi          0B       2.0Gi

3. Show output in megabytes

free -m

4. Show output in gigabytes

free -g

5. Watch memory usage over time (every 5 seconds)

free -h -s 5

6. Include total line at the end

free -h -t

Practical Tip

If you’re wondering how much memory your apps can still use, focus on the available column, not just the free one. Linux uses free memory for cache to speed up the system, but it will release that cache if needed by applications.

For more info, check the man page:

man free