Find Real OSM Size

Ever spent alot of time editing to reduce file size, but when you saved your .OSM, it used almost as many kilobyte as before? Most likely the reason you don’t see the KB shrink by much is because SM has ZIP compression turned on. You cannot use zippped file size to compare reduction, since the nature of compression is to replace cloned sections with tokens. Since most schematics are full of cloned programming, they tend to ZIP well. For example: if 1 module will be 5KB zipped but 10KB in reality uncompressed, then 50 of the same module may be only 20Kb zipped, but 500KB in reality (not 100% true example).

Here is an easy way for you find the actual uncompressed file size of your schematic.

1: Install 7zip

Go to to download the latest free version of 7zip. Install.
BTW: Betas tend to be stable, but there is still a risk.

2: Open your .OSM in 7zip

Find your .OSM, right click over the file name, select 7-zip > Open Archive like this:

3: Read Size

You should see only one item called “schematic.osm” with a column named “Size” and “Packed Size”. That schematic.osm is the actual file SM uses after it unZIPs the .OSM. The “Size” is the actual uncompressed file size that you need to compare with the original’s .OSM using the same steps again. You will find that items with many synchronized modules will compress very well, like in the case of this ADSR:

tutorials/find_real_osm_size.txt · Last modified: 2008/12/02 06:25 by infuzion