How to measure Windows 7 memory usage

Task Manager: easy and incomplete

The simplest way to get a quick and dirty picture of how memory is being used is to open Task Manager (press Ctrl+Shift+Esc) and click the Performance tab. The bar under the Memory heading shows how much physical memory is currently in use by active processes, including the operating system.

For more details, see Windows 7 memory usage: What’s the best way to measure?