Ask Ubuntu is a question and answer site for Ubuntu users and developers. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

While I am looking at man page of free I came across

--si   Use power of 1000 not 1024.

So from that line we can say that from 1GB (1024MB) of RAM it will use only 1000MB of RAM. But why are we supposed to do like that? where we can use this ? If we do so what will happen to remaining 24 MB. What exactly it supposed to be?

Thank you.

share|improve this question

"si" is used for measurement.

Currently only Mac OS X uses "si" for measurement.
(Note that "free" only shows your free memory, it does not set anything.)

Think about it this way...
When you buy something, it's 120GB. For example. That's si.
When you format it and use it on Windows/Ubuntu, you will see that it's smaller than that.
(Si is one of the reasons. There are others, like the "reserved disk space" with ext3/4 and so on. But it's a simple example.)

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.