On Tue, Jun 15, 2010 at 20:38:56 -0500, Richard Shaw <hobbes1069 at gmail.com> wrote: > 3 iso_size = math.ceil(file_size/(2*1024))*2*1024 With loose typing the about might be doing the division as integer division. One possible fix would be: iso_size = ((file_size + ((2*1024)-1))/(2*1024))*(2*1024)