IPv4 Subnet Mask Cheat Sheet

A complete reference for all IPv4 subnet masks from /1 to /32, including usable host counts, wildcard masks, and binary representations.

Quick reference table

CIDR	Subnet mask	Wildcard mask	Usable hosts	Network bits	Host bits
/8	255.0.0.0	0.255.255.255	16,777,214	8	24
/9	255.128.0.0	0.127.255.255	8,388,606	9	23
/10	255.192.0.0	0.63.255.255	4,194,302	10	22
/11	255.224.0.0	0.31.255.255	2,097,150	11	21
/12	255.240.0.0	0.15.255.255	1,048,574	12	20
/13	255.248.0.0	0.7.255.255	524,286	13	19
/14	255.252.0.0	0.3.255.255	262,142	14	18
/15	255.254.0.0	0.1.255.255	131,070	15	17
/16	255.255.0.0	0.0.255.255	65,534	16	16
/17	255.255.128.0	0.0.127.255	32,766	17	15
/18	255.255.192.0	0.0.63.255	16,382	18	14
/19	255.255.224.0	0.0.31.255	8,190	19	13
/20	255.255.240.0	0.0.15.255	4,094	20	12
/21	255.255.248.0	0.0.7.255	2,046	21	11
/22	255.255.252.0	0.0.3.255	1,022	22	10
/23	255.255.254.0	0.0.1.255	510	23	9
/24	255.255.255.0	0.0.0.255	254	24	8
/25	255.255.255.128	0.0.0.127	126	25	7
/26	255.255.255.192	0.0.0.63	62	26	6
/27	255.255.255.224	0.0.0.31	30	27	5
/28	255.255.255.240	0.0.0.15	14	28	4
/29	255.255.255.248	0.0.0.7	6	29	3
/30	255.255.255.252	0.0.0.3	2	30	2
/31	255.255.255.254	0.0.0.1	2*	31	1
/32	255.255.255.255	0.0.0.0	1**	32	0

*RFC 3021 point-to-point links. **Host route.

Private IP ranges (RFC 1918)

Range	CIDR	Addresses
10.0.0.0 – 10.255.255.255	10.0.0.0/8	16,777,216
172.16.0.0 – 172.31.255.255	172.16.0.0/12	1,048,576
192.168.0.0 – 192.168.255.255	192.168.0.0/16	65,536

Special ranges

Range	Purpose
127.0.0.0/8	Loopback
169.254.0.0/16	Link-local (APIPA)
224.0.0.0/4	Multicast (Class D)
240.0.0.0/4	Reserved (Class E)
0.0.0.0/0	Default route

How to calculate subnet masks

To convert a CIDR prefix to a subnet mask: set the first N bits to 1, the remaining 32-N bits to 0, then convert each 8-bit group to decimal.

Example for /26:

• Binary: 11111111.11111111.11111111.11000000
• Decimal: 255.255.255.192

Use our subnet calculator to compute any subnet instantly.