On Windows, open Task Manager with Ctrl + Shift + Esc, then go to Performance > Memory
On Windows, open Settings > System > About and check Installed RAM
On Mac, click the Apple menu > About This Mac and check Memory
On Linux, open a terminal and run free -h
On Linux, open a terminal and run cat /proc/meminfo
On Linux, use a system info tool such as lshw or inxi
Check your computer’s system information or specifications page
Check your BIOS or UEFI setup screen during startup
Open the computer case and read the RAM module labels if needed