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Subnet mask cheat sheet

Every IPv4 prefix length with its subnet mask, wildcard mask and size, the IPv6 prefix sizes in everyday use, and a calculator for any address and prefix. Print it, or keep the page open.

Subnet calculator

For example 10.0.0.0/8, 172.16.4.9/22, or an address and mask: 192.168.1.1 255.255.255.0

IPv4 subnet masks

Usable hosts excludes the network and broadcast addresses, except on a /31, where both addresses are usable on a point-to-point link, and a /32, which is one host.

PrefixSubnet maskWildcard maskAddressesUsable hostsHexNote
/32 255.255.255.255 0.0.0.0 1 1 0xFFFFFFFF Single host
/31 255.255.255.254 0.0.0.1 2 2 0xFFFFFFFE Point-to-point link (RFC 3021)
/30 255.255.255.252 0.0.0.3 4 2 0xFFFFFFFC Point-to-point link, traditional
/29 255.255.255.248 0.0.0.7 8 6 0xFFFFFFF8
/28 255.255.255.240 0.0.0.15 16 14 0xFFFFFFF0
/27 255.255.255.224 0.0.0.31 32 30 0xFFFFFFE0
/26 255.255.255.192 0.0.0.63 64 62 0xFFFFFFC0
/25 255.255.255.128 0.0.0.127 128 126 0xFFFFFF80
/24 255.255.255.0 0.0.0.255 256 254 0xFFFFFF00 Former class C
/23 255.255.254.0 0.0.1.255 512 510 0xFFFFFE00
/22 255.255.252.0 0.0.3.255 1,024 1,022 0xFFFFFC00
/21 255.255.248.0 0.0.7.255 2,048 2,046 0xFFFFF800
/20 255.255.240.0 0.0.15.255 4,096 4,094 0xFFFFF000
/19 255.255.224.0 0.0.31.255 8,192 8,190 0xFFFFE000
/18 255.255.192.0 0.0.63.255 16,384 16,382 0xFFFFC000
/17 255.255.128.0 0.0.127.255 32,768 32,766 0xFFFF8000
/16 255.255.0.0 0.0.255.255 65,536 65,534 0xFFFF0000 Former class B
/15 255.254.0.0 0.1.255.255 131,072 131,070 0xFFFE0000
/14 255.252.0.0 0.3.255.255 262,144 262,142 0xFFFC0000
/13 255.248.0.0 0.7.255.255 524,288 524,286 0xFFF80000
/12 255.240.0.0 0.15.255.255 1,048,576 1,048,574 0xFFF00000
/11 255.224.0.0 0.31.255.255 2,097,152 2,097,150 0xFFE00000
/10 255.192.0.0 0.63.255.255 4,194,304 4,194,302 0xFFC00000
/9 255.128.0.0 0.127.255.255 8,388,608 8,388,606 0xFF800000
/8 255.0.0.0 0.255.255.255 16,777,216 16,777,214 0xFF000000 Former class A
/7 254.0.0.0 1.255.255.255 33,554,432 33,554,430 0xFE000000
/6 252.0.0.0 3.255.255.255 67,108,864 67,108,862 0xFC000000
/5 248.0.0.0 7.255.255.255 134,217,728 134,217,726 0xF8000000
/4 240.0.0.0 15.255.255.255 268,435,456 268,435,454 0xF0000000
/3 224.0.0.0 31.255.255.255 536,870,912 536,870,910 0xE0000000
/2 192.0.0.0 63.255.255.255 1,073,741,824 1,073,741,822 0xC0000000
/1 128.0.0.0 127.255.255.255 2,147,483,648 2,147,483,646 0x80000000
/0 0.0.0.0 255.255.255.255 4,294,967,296 4,294,967,294 0x00000000 Default route

IPv6 prefix sizes

IPv6 is planned in /64 subnets rather than host counts: every LAN is a /64, and sites are given a block of them.

Prefix/64 subnetsContainsTypical use
/128 – A single address: a loopback or a host route
/127 – Point-to-point link between two routers (RFC 6164)
/64 1 One subnet: the standard size for a LAN, required for SLAAC
/60 16 A small site
/56 256 A typical end-site assignment, e.g. a home or small office
/52 4,096 16 × /56 A larger site
/48 65,536 256 × /56 A typical business site assignment
/44 1,048,576 16 × /48 A group of sites
/40 16,777,216 256 × /48 A regional or campus block
/32 4,294,967,296 65,536 × /48 A large network or ISP block
/29 34,359,738,368 524,288 × /48 The usual initial allocation to a RIPE NCC member

Special-purpose ranges

RangePurposeDefined in
10.0.0.0/8Private networkRFC 1918
172.16.0.0/12Private networkRFC 1918
192.168.0.0/16Private networkRFC 1918
100.64.0.0/10Shared address space for carrier-grade NATRFC 6598
127.0.0.0/8LoopbackRFC 1122
169.254.0.0/16Link-localRFC 3927
192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24Documentation and examplesRFC 5737
224.0.0.0/4MulticastRFC 5771
fc00::/7IPv6 unique local addressesRFC 4193
fe80::/10IPv6 link-localRFC 4291
2001:db8::/32IPv6 documentationRFC 3849

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