hda1    c:                  FAT32               1G
hda2    /boot               EXT2                75M
hda3    extendida
hda4    d: (/mnt/win_D)     VFAT                5G
hda5    /home               XFS                 2G
hda6    /musicas            VFAT Read Only      12G
hda7    swap                SWAP                1G
hda8    /var                XFS                 2.5G
hda9    /                   XFS                 14065M

38204 - (1024 + 75 + (1024*5) + (1024*2) + (1024*12) + 1024 + (1024 *2.5))
14065.0

 device size with M = 1024*1024:       38204 MBytes
 device size with M = 1000*1000:       40060 MBytes (40 GB)