Subnet Mask Cheatsheet

CIDR Notation Reference Table

This table shows the relationship between CIDR notation, subnet masks, available hosts, and the percentage of a Class C network.

CIDR	Hosts	Netmask	Amount of a Class C
/30	2	255.255.255.252	1/64
/29	6	255.255.255.248	1/32
/28	14	255.255.255.240	1/16
/27	30	255.255.255.224	1/8
/26	62	255.255.255.192	1/4
/25	126	255.255.255.128	1/2
/24	254	255.255.255.0	1
/23	510	255.255.254.0	2
/22	1,022	255.255.252.0	4
/21	2,046	255.255.248.0	8
/20	4,094	255.255.240.0	16
/19	8,190	255.255.224.0	32
/18	16,382	255.255.192.0	64
/17	32,766	255.255.128.0	128
/16	65,534	255.255.0.0	256

Guide to Sub-Class C Blocks

The following tables show the network ranges for various subnet masks within a Class C network.