How to check RAM size?
From a terminal you should be able to use:
free -m
From man page:
-m,--mebiDisplay the amount of memory in mebibytes.
--megaDisplay the amount of memory in megabytes. Implies--si.
Note: A kilobyte (kB) is 1000 Bytes.
Open a terminal (CTRL + ALT + T)...
Run following command to see RAM information in KB (1 KB is equal to 1024 bytes).
free
Run following command to see RAM information in MB (1 MB is equal to 1024 KB).
free -m
Run following command to see RAM information in GB (1 GB is equal to 1024 MB).
free -g
Or you can run following command to see more information about the same:
free -h
Click on the power/gear icon (System Menu) in the top right corner of the screen and choose About This Computer. You will see the total available memory in GiB. Multiply the value by 1024 to get the size in MiB.
This value (and the value shown as Total in output of free -m on the console), is total physical RAM size, minus the amount assigned to the internal GPU, if your computer has one.
To see the total amount of physical RAM installed, you can run sudo lshw -c memory which will show you each individual bank of RAM you have installed, as well as the total size for the System Memory. This will likely presented as GiB value, which you can again multiply by 1024 to get the MiB value.