# Matlab and memory use

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F.O on 23 Oct 2017
Edited: Reza Bonyadi on 24 Oct 2017
Hi, How I can compute how much RAM memory this matrix rand(500,500) take?

Cedric Wannaz on 23 Oct 2017
Edited: Cedric Wannaz on 23 Oct 2017
MATLAB default numeric type/class is "double" (for double-precision floating-point) stored on 8 bytes (= 64 bits). Your array will contain 500 x 500 "double" elements, and the size in byte is the number of elements times the size per element in byte, hence:
>> 500 * 500 * 8
ans =
2000000
which is in MB (megabyte):
>> 500 * 500 * 8 / 1e6
ans =
2

Reza Bonyadi on 23 Oct 2017
Edited: Reza Bonyadi on 24 Oct 2017
xx= rand(500,500); h=whos('xx');
h.bytes is what you want then. This is an estimate, as there might be some compressions in place during the usage of the variable. Note that, as different variable may have different types (int, double, ...), whos is a good option as it considers the real size and not sensitive to the type. For example, xx=int8(randi(100,500));h=whos('xx');h.bytes gives you 250,000 while the previous example gives you 2,000,000. So you dont need to know how many bytes are considered for each type in Matlab.