Subnet mask v.s. CIDR

Netmask                  Netmask (binary)             CIDR     Notes    
 _____________________________________________________________________________ 
255.255.255.255  11111111.11111111.11111111.11111111  /32  Host (single addr) 
255.255.255.254  11111111.11111111.11111111.11111110  /31  Unuseable 
255.255.255.252  11111111.11111111.11111111.11111100  /30    2  useable 
255.255.255.248  11111111.11111111.11111111.11111000  /29    6  useable 
255.255.255.240  11111111.11111111.11111111.11110000  /28   14  useable 
255.255.255.224  11111111.11111111.11111111.11100000  /27   30  useable 
255.255.255.192  11111111.11111111.11111111.11000000  /26   62  useable 
255.255.255.128  11111111.11111111.11111111.10000000  /25  126  useable 
255.255.255.0    11111111.11111111.11111111.00000000  /24 "Class C" 254 useable  
255.255.254.0    11111111.11111111.11111110.00000000  /23    2  Class C's 
255.255.252.0    11111111.11111111.11111100.00000000  /22    4  Class C's 
255.255.248.0    11111111.11111111.11111000.00000000  /21    8  Class C's 
255.255.240.0    11111111.11111111.11110000.00000000  /20   16  Class C's 
255.255.224.0    11111111.11111111.11100000.00000000  /19   32  Class C's 
255.255.192.0    11111111.11111111.11000000.00000000  /18   64  Class C's 
255.255.128.0    11111111.11111111.10000000.00000000  /17  128  Class C's 
255.255.0.0      11111111.11111111.00000000.00000000  /16  "Class B"       
255.254.0.0      11111111.11111110.00000000.00000000  /15    2  Class B's 
255.252.0.0      11111111.11111100.00000000.00000000  /14    4  Class B's 
255.248.0.0      11111111.11111000.00000000.00000000  /13    8  Class B's 
255.240.0.0      11111111.11110000.00000000.00000000  /12   16  Class B's 
255.224.0.0      11111111.11100000.00000000.00000000  /11   32  Class B's 
255.192.0.0      11111111.11000000.00000000.00000000  /10   64  Class B's 
255.128.0.0      11111111.10000000.00000000.00000000  /9   128  Class B's 
255.0.0.0        11111111.00000000.00000000.00000000  /8   "Class A"   
254.0.0.0        11111110.00000000.00000000.00000000  /7 
252.0.0.0        11111100.00000000.00000000.00000000  /6 
248.0.0.0        11111000.00000000.00000000.00000000  /5 
240.0.0.0        11110000.00000000.00000000.00000000  /4 
224.0.0.0        11100000.00000000.00000000.00000000  /3 
192.0.0.0        11000000.00000000.00000000.00000000  /2 
128.0.0.0        10000000.00000000.00000000.00000000  /1 
0.0.0.0          00000000.00000000.00000000.00000000  /0   IP space