Subnet Mask Information

Number of Addresses	Number of Bits	Prefix	Classful Notation	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