Subnet masks' list:
addrs bits pref classf mask
1 0 /32 255.255.255.255
2 1 /31 255.255.255.254
4 2 /30 255.255.255.252
8 3 /29 255.255.255.248
16 4 /28 255.255.255.240
32 5 /27 255.255.255.224
64 6 /26 255.255.255.192
128 7 /25 255.255.255.128
256 8 /24 1 C 255.255.255
512 9 /23 2 C 255.255.254
1 K 10 /22 4 C 255.255.252
2 K 11 /21 8 C 255.255.248
4 K 12 /20 16 C 255.255.240
8 K 13 /19 32 C 255.255.224
16 K 14 /18 64 C 255.255.192
32 K 15 /17 128 C 255.255.128
64 K 16 /16 1 B 255.255
128 K 17 /15 2 B 255.254
256 K 18 /14 4 B 255.252
512 K 19 /13 8 B 255.248
1 M 20 /12 16 B 255.240
2 M 21 /11 32 B 255.224
4 M 22 /10 64 B 255.192
8 M 23 /9 128 B 255.128
16 M 24 /8 1 A 255
32 M 25 /7 2 A 254
64 M 26 /6 4 A 252
128 M 27 /5 8 A 248
256 M 28 /4 16 A 240
512 M 29 /3 32 A 224
1024 M 30 /2 64 A 192
hosts subn/c subn/c subn/b subn/b bits hex-mask dec-mask
strict strict
2 64 62 16384 16382 2 fffffffc 255.255.255.252
6 32 30 8192 8190 3 fffffff8 255.255.255.248
14 16 14 4096 4094 4 fffffff0 255.255.255.240
30 8 6 2048 2046 5 ffffffe0 255.255.255.224
62 4 2 1024 1022 6 ffffffc0 255.255.255.192
126 2 0 512 510 7 ffffff80 255.255.255.128
254 256 254 8 ffffff00 255.255.255.0
510 128 126 9 fffffe00 255.255.254.0
1022 64 62 10 fffffc00 255.255.252.0
2046 32 30 11 fffff800 255.255.248.0
4094 16 14 12 fffff000 255.255.240.0
8190 8 6 13 ffffe000 255.255.224.0
16382 4 2 14 ffffc000 255.255.192.0
32766 2 0 15 ffff8000 255.255.128.0
You can also find this list in the following document: European
Internet Registry Policies and Procedures, section 9.Glossary at:
http://www.ripe.net/ripe/docs/ir-policies-procedures.html#toc87