Free command displays information about the physical (RAM) and swap memory of your system.

In the example below, the total physical memory displayed below are in KB.

root@cloud1:~# free
             total       used       free     shared    buffers     cached
Mem:        262144     193900      68244          0          0      42964
-/+ buffers/cache:     150936     111208
Swap:       524288     186196     338092

The following example will display the total memory on your system including RAM and Swap.

In the following command:

option m displays the values in MB
option t displays the “Total” line, which is sum of physical and swap memory values
option o is to hide the buffers/cache line from the above example.

root@cloud1:~# free -mto
             total       used       free     shared    buffers     cached
Mem:           256        189         66          0          0         41
Swap:          512        181        330
Total:         768        371        396
root@cloud1:~#

root@server10 [/home]# free -m
             total       used       free     shared    buffers     cached
Mem:          7946       7772        173          0        235       2492
-/+ buffers/cache:       5044       2901
Swap:         2047        786       1261
root@server10 [/home]#