Subnet Cheat Sheet

The tables below are commonly used subnet masks and hosts.

Class C
Mask	Notation	Subnets	Hosts
255.255.255.0	/24	1	256
255.255.255.128	/25	2	128
255.255.255.192	/26	4	64
255.255.255.224	/27	8	32
255.255.255.240	/28	16	16
255.255.255.248	/29	32	8
255.255.255.252	/30	64	4
255.255.255.254	/31	128	2
255.255.255.255	/32	256	1
Class B
Mask	Notation	Subnets	Hosts
255.255.0.0	/16	1	65,536
255.255.128.0	/17	2	32,768
255.255.192.0	/18	4	16,384
255.255.224.0	/19	8	8,192
255.255.240.0	/20	16	4,096
255.255.248.0	/21	32	2,048
255.255.252.0	/22	64	1,024
255.255.254.0	/23	128	512
255.255.255.0	/24	256	256
Class A
Mask	Notation	Subnets	Hosts
255.0.0.0	/8	1	16,777,216
255.128.0.0	/9	2	8,388,608
255.192.0.0	/10	4	4,194,304
255.224.0.0	/11	8	2,097,152
255.240.0.0	/12	16	1,048,576
255.248.0.0	/13	32	524,288
255.252.0.0	/14	64	262,144
255.254.0.0	/15	128	131,072
255.255.0.0	/16	256	65,536