Linux is borrowing unused memory for disk caching. This makes it looks like you are low on memory, but you are not! Everything is fine!

How do I see how much free ram I really have?

To see how much ram is free to use for your applications, run free -m and look at the row that says “-/+ buffers/cache” in the column that says “free”. That is your answer in megabytes:

$ free -m
             total       used       free     shared    buffers     cached
Mem:          1504       1491         13          0         91        764
-/+ buffers/cache:        635        869
Swap:         2047          6       2041

If you don’t know how to read the numbers, you’ll think the ram is 99% full when it’s really just 42%.