Subnet Mask Cheat Sheet

See also RFC 1878.

AddressesHostsNetmaskAmount of a Class C
/3042255.255.255.2521/64
/2986255.255.255.2481/32
/281614255.255.255.2401/16
/273230255.255.255.2241/8
/266462255.255.255.1921/4
/25128126255.255.255.1281/2
/24256254255.255.255.01
/23512510255.255.254.02
/2210241022255.255.252.04
/2120482046255.255.248.08
/2040964094255.255.240.016
/1981928190255.255.224.032
/181638416382255.255.192.064
/173276832766255.255.128.0128
/166553665534255.255.0.0256

Guide to sub-class C blocks

/25 -- 2 Subnets -- 126 Hosts/Subnet

Network #IP RangeBroadcast
.0.1-.126.127
.128.129-.254.255

/30 -- 64 Subnets -- 2 Hosts/Subnet

Network #IP RangeBroadcast
.0.1-.2.3
.4.5-.6.7
.8.9-.10.11
.12.13-.14.15
.16.17-.18.19
.20.21-.22.23
.24.25-.26.27
.28.29-.30.31
.32.33-.34.35
.36.37-.38.39
.40.41-.42.43
.44.45-.46.47
.48.49-.50.51
.52.53-.54.55
.56.57-.58.59
.60.61-.62.63
.64.65-.66.67
.68.69-.70.71
.72.73-.74.75
.76.77-.78.79
.80.81-.82.83
.84.85-.86.87
.88.89-.90.91
.92.93-.94.95
.96.97-.98.99
.100.101-.102.103
.104.105-.106.107
.108.109-.110.111
.112.113-.114.115
.116.117-.118.119
.120.121-.122.123
.124.125-.126.127
.128.129-.130.131
.132.133-.134.135
.136.137-.138.139
.140.141-.142.143
.144.145-.146.147
.148.149-.150.151
.152.153-.154.155
.156.157-.158.159
.160.161-.162.163
.164.165-.166.167
.168.169-.170.171
.172.173-.174.175
.176.177-.178.179
.180.181-.182.183
.184.185-.186.187
.188.189-.190.191
.192.193-.194.195
.196.197-.198.199
.200.201-.202.203
.204.205-.206.207
.208.209-.210.211
.212.213-.214.215
.216.217-.218.219
.220.221-.222.223
.224.225-.226.227
.228.229-.230.231
.232.233-.234.235
.236.237-.238.239
.240.241-.242.243
.244.245-.246.247
.248.249-.250.251
.252.253-.254.255

/26 -- 4 Subnets -- 62 Hosts/Subnet

Network #IP RangeBroadcast
.0.1-.62.63
.64.65-.126.127
.128.129-.190.191
.192.193-.254.255

/27 -- 8 Subnets -- 30 Hosts/Subnet

Network #IP RangeBroadcast
.0.1-.30.31
.32.33-.62.63
.64.65-.94.95
.96.97-.126.127
.128.129-.158.159
.160.161-.190.191
.192.193-.222.223
.224.225-.254.255

/28 -- 16 Subnets -- 14 Hosts/Subnet

Network #IP RangeBroadcast
.0.1-.14.15
.16.17-.30.31
.32.33-.46.47
.48.49-.62.63
.64.65-.78.79
.80.81-.94.95
.96.97-.110.111
.112.113-.126.127
.128.129-.142.143
.144.145-.158.159
.160.161-.174.175
.176.177-.190.191
.192.193-.206.207
.208.209-.222.223
.224.225-.238.239
.240.241-.254.255

/29 -- 32 Subnets -- 6 Hosts/Subnet

Network #IP RangeBroadcast
.0.1-.6.7
.8.9-.14.15
.16.17-.22.23
.24.25-.30.31
.32.33-.38.39
.40.41-.46.47
.48.49-.54.55
.56.57-.62.63
.64.65-.70.71
.72.73-.78.79
.80.81-.86.87
.88.89-.94.95
.96.97-.102.103
.104.105-.110.111
.112.113-.118.119
.120.121-.126.127
.128.129-.134.135
.136.137-.142.143
.144.145-.150.151
.152.153-.158.159
.160.161-.166.167
.168.169-.174.175
.176.177-.182.183
.184.185-.190.191
.192.193-.198.199
.200.201-.206.207
.208.209-.214.215
.216.217-.222.223
.224.225-.230.231
.232.233-.238.239
.240.241-.246.247
.248.249-.254.255
   The following table lists the variable length subnets from 1 to 32,
   the CIDR [3] representation form (/xx) and the Decmial equivalents.
   (M = Million, K=Thousand, A,B,C= traditional class values)

   Mask value:                             # of
   Hex            CIDR   Decimal           addresses  Classfull
   80.00.00.00    /1     128.0.0.0         2048 M     128 A
   C0.00.00.00    /2     192.0.0.0         1024 M      64 A
   E0.00.00.00    /3     224.0.0.0          512 M      32 A
   F0.00.00.00    /4     240.0.0.0          256 M      16 A
   F8.00.00.00    /5     248.0.0.0          128 M       8 A
   FC.00.00.00    /6     252.0.0.0           64 M       4 A
   FE.00.00.00    /7     254.0.0.0           32 M       2 A
   FF.00.00.00    /8     255.0.0.0           16 M       1 A
   FF.80.00.00    /9     255.128.0.0          8 M     128 B
   FF.C0.00.00   /10     255.192.0.0          4 M      64 B
   FF.E0.00.00   /11     255.224.0.0          2 M      32 B
   FF.F0.00.00   /12     255.240.0.0       1024 K      16 B
   FF.F8.00.00   /13     255.248.0.0        512 K       8 B
   FF.FC.00.00   /14     255.252.0.0        256 K       4 B
   FF.FE.00.00   /15     255.254.0.0        128 K       2 B
   FF.FF.00.00   /16     255.255.0.0         64 K       1 B
   FF.FF.80.00   /17     255.255.128.0       32 K     128 C
   FF.FF.C0.00   /18     255.255.192.0       16 K      64 C
   FF.FF.E0.00   /19     255.255.224.0        8 K      32 C
   FF.FF.F0.00   /20     255.255.240.0        4 K      16 C
   FF.FF.F8.00   /21     255.255.248.0        2 K       8 C
   FF.FF.FC.00   /22     255.255.252.0        1 K       4 C
   FF.FF.FE.00   /23     255.255.254.0      512         2 C
   FF.FF.FF.00   /24     255.255.255.0      256         1 C
   FF.FF.FF.80   /25     255.255.255.128    128       1/2 C
   FF.FF.FF.C0   /26     255.255.255.192     64       1/4 C
   FF.FF.FF.E0   /27     255.255.255.224     32       1/8 C
   FF.FF.FF.F0   /28     255.255.255.240     16      1/16 C
   FF.FF.FF.F8   /29     255.255.255.248      8      1/32 C
   FF.FF.FF.FC   /30     255.255.255.252      4      1/64 C
   FF.FF.FF.FE   /31     255.255.255.254      2     1/128 C
   FF.FF.FF.FF   /32     255.255.255.255   This is a single host route

Private IPv4 address spaces

The Internet Engineering Task Force (IETF) has directed the Internet Assigned Numbers Authority (IANA) to reserve the following IPv4 address ranges for private networks, as published in RFC 1918

RFC1918 name IP address range number of addresses largest CIDR block (subnet mask) host id size mask bits classful description
24-bit block 10.0.0.0 - 10.255.255.255 16,777,216 10.0.0.0/8 (255.0.0.0) 24 bits 8 bits single Class A network
20-bit block 172.16.0.0 - 172.31.255.255 1,048,576 172.16.0.0/12 (255.240.0.0) 20 bits 12 bits 16 contiguous class B networks
16-bit block 192.168.0.0 - 192.168.255.255 65,536 192.168.0.0/16 (255.255.0.0) 16 bits 16 bits 256 contiguous class C networks