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IP subnet calculator

Type an address with its prefix or mask to see the network, its usable range and masks. Split it into smaller subnets, or look up any prefix in the reference tables.

Network24.131.40.0/21
Usable hosts2,046
Subnet mask255.255.248.0
Addresses2,048
Network address
24.131.40.0
Broadcast address
24.131.47.255
First usable
24.131.40.1
Last usable
24.131.47.254
Usable hosts
2,046 (2,048 less the network and broadcast addresses)
Subnet mask
255.255.248.0
Wildcard mask
0.0.7.255 (Cisco ACLs, OSPF)
Prefix length
/21
Type
Public public
Old class
A (default /8)
As numbers
Hex 18832800 · Integer 411248640 to 411250687
Reverse DNS zones
40.131.24.in-addr.arpa
41.131.24.in-addr.arpa
42.131.24.in-addr.arpa
43.131.24.in-addr.arpa
44.131.24.in-addr.arpa
45.131.24.in-addr.arpa
46.131.24.in-addr.arpa
47.131.24.in-addr.arpa
/21 is not on a 8-bit boundary, so it takes 8 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00011000.10000011.00101000.0000000024.131.40.0
Subnet mask11111111.11111111.11111000.00000000255.255.248.0
Network00011000.10000011.00101000.0000000024.131.40.0
Broadcast00011000.10000011.00101111.1111111124.131.47.255
Split into smaller subnets/32
/22 (2)/23 (4)/24 (8)/25 (16)/26 (32)/27 (64)/28 (128)/29 (256)/30 (512)/31 (1,024)/32 (2,048)

24.131.40.0/21 makes 2,048 subnets of /32; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
124.131.40.0/3224.131.40.0 to 24.131.40.0—1
224.131.40.1/3224.131.40.1 to 24.131.40.1—1
324.131.40.2/3224.131.40.2 to 24.131.40.2—1
424.131.40.3/3224.131.40.3 to 24.131.40.3—1
524.131.40.4/3224.131.40.4 to 24.131.40.4—1
624.131.40.5/3224.131.40.5 to 24.131.40.5—1
724.131.40.6/3224.131.40.6 to 24.131.40.6—1
824.131.40.7/3224.131.40.7 to 24.131.40.7—1
924.131.40.8/3224.131.40.8 to 24.131.40.8—1
1024.131.40.9/3224.131.40.9 to 24.131.40.9—1
1124.131.40.10/3224.131.40.10 to 24.131.40.10—1
1224.131.40.11/3224.131.40.11 to 24.131.40.11—1
1324.131.40.12/3224.131.40.12 to 24.131.40.12—1
1424.131.40.13/3224.131.40.13 to 24.131.40.13—1
1524.131.40.14/3224.131.40.14 to 24.131.40.14—1
1624.131.40.15/3224.131.40.15 to 24.131.40.15—1
1724.131.40.16/3224.131.40.16 to 24.131.40.16—1
1824.131.40.17/3224.131.40.17 to 24.131.40.17—1
1924.131.40.18/3224.131.40.18 to 24.131.40.18—1
2024.131.40.19/3224.131.40.19 to 24.131.40.19—1
2124.131.40.20/3224.131.40.20 to 24.131.40.20—1
2224.131.40.21/3224.131.40.21 to 24.131.40.21—1
2324.131.40.22/3224.131.40.22 to 24.131.40.22—1
2424.131.40.23/3224.131.40.23 to 24.131.40.23—1
2524.131.40.24/3224.131.40.24 to 24.131.40.24—1
2624.131.40.25/3224.131.40.25 to 24.131.40.25—1
2724.131.40.26/3224.131.40.26 to 24.131.40.26—1
2824.131.40.27/3224.131.40.27 to 24.131.40.27—1
2924.131.40.28/3224.131.40.28 to 24.131.40.28—1
3024.131.40.29/3224.131.40.29 to 24.131.40.29—1
3124.131.40.30/3224.131.40.30 to 24.131.40.30—1
3224.131.40.31/3224.131.40.31 to 24.131.40.31—1
3324.131.40.32/3224.131.40.32 to 24.131.40.32—1
3424.131.40.33/3224.131.40.33 to 24.131.40.33—1
3524.131.40.34/3224.131.40.34 to 24.131.40.34—1
3624.131.40.35/3224.131.40.35 to 24.131.40.35—1
3724.131.40.36/3224.131.40.36 to 24.131.40.36—1
3824.131.40.37/3224.131.40.37 to 24.131.40.37—1
3924.131.40.38/3224.131.40.38 to 24.131.40.38—1
4024.131.40.39/3224.131.40.39 to 24.131.40.39—1
4124.131.40.40/3224.131.40.40 to 24.131.40.40—1
4224.131.40.41/3224.131.40.41 to 24.131.40.41—1
4324.131.40.42/3224.131.40.42 to 24.131.40.42—1
4424.131.40.43/3224.131.40.43 to 24.131.40.43—1
4524.131.40.44/3224.131.40.44 to 24.131.40.44—1
4624.131.40.45/3224.131.40.45 to 24.131.40.45—1
4724.131.40.46/3224.131.40.46 to 24.131.40.46—1
4824.131.40.47/3224.131.40.47 to 24.131.40.47—1
4924.131.40.48/3224.131.40.48 to 24.131.40.48—1
5024.131.40.49/3224.131.40.49 to 24.131.40.49—1
5124.131.40.50/3224.131.40.50 to 24.131.40.50—1
5224.131.40.51/3224.131.40.51 to 24.131.40.51—1
5324.131.40.52/3224.131.40.52 to 24.131.40.52—1
5424.131.40.53/3224.131.40.53 to 24.131.40.53—1
5524.131.40.54/3224.131.40.54 to 24.131.40.54—1
5624.131.40.55/3224.131.40.55 to 24.131.40.55—1
5724.131.40.56/3224.131.40.56 to 24.131.40.56—1
5824.131.40.57/3224.131.40.57 to 24.131.40.57—1
5924.131.40.58/3224.131.40.58 to 24.131.40.58—1
6024.131.40.59/3224.131.40.59 to 24.131.40.59—1
6124.131.40.60/3224.131.40.60 to 24.131.40.60—1
6224.131.40.61/3224.131.40.61 to 24.131.40.61—1
6324.131.40.62/3224.131.40.62 to 24.131.40.62—1
6424.131.40.63/3224.131.40.63 to 24.131.40.63—1
6524.131.40.64/3224.131.40.64 to 24.131.40.64—1
6624.131.40.65/3224.131.40.65 to 24.131.40.65—1
6724.131.40.66/3224.131.40.66 to 24.131.40.66—1
6824.131.40.67/3224.131.40.67 to 24.131.40.67—1
6924.131.40.68/3224.131.40.68 to 24.131.40.68—1
7024.131.40.69/3224.131.40.69 to 24.131.40.69—1
7124.131.40.70/3224.131.40.70 to 24.131.40.70—1
7224.131.40.71/3224.131.40.71 to 24.131.40.71—1
7324.131.40.72/3224.131.40.72 to 24.131.40.72—1
7424.131.40.73/3224.131.40.73 to 24.131.40.73—1
7524.131.40.74/3224.131.40.74 to 24.131.40.74—1
7624.131.40.75/3224.131.40.75 to 24.131.40.75—1
7724.131.40.76/3224.131.40.76 to 24.131.40.76—1
7824.131.40.77/3224.131.40.77 to 24.131.40.77—1
7924.131.40.78/3224.131.40.78 to 24.131.40.78—1
8024.131.40.79/3224.131.40.79 to 24.131.40.79—1
8124.131.40.80/3224.131.40.80 to 24.131.40.80—1
8224.131.40.81/3224.131.40.81 to 24.131.40.81—1
8324.131.40.82/3224.131.40.82 to 24.131.40.82—1
8424.131.40.83/3224.131.40.83 to 24.131.40.83—1
8524.131.40.84/3224.131.40.84 to 24.131.40.84—1
8624.131.40.85/3224.131.40.85 to 24.131.40.85—1
8724.131.40.86/3224.131.40.86 to 24.131.40.86—1
8824.131.40.87/3224.131.40.87 to 24.131.40.87—1
8924.131.40.88/3224.131.40.88 to 24.131.40.88—1
9024.131.40.89/3224.131.40.89 to 24.131.40.89—1
9124.131.40.90/3224.131.40.90 to 24.131.40.90—1
9224.131.40.91/3224.131.40.91 to 24.131.40.91—1
9324.131.40.92/3224.131.40.92 to 24.131.40.92—1
9424.131.40.93/3224.131.40.93 to 24.131.40.93—1
9524.131.40.94/3224.131.40.94 to 24.131.40.94—1
9624.131.40.95/3224.131.40.95 to 24.131.40.95—1
9724.131.40.96/3224.131.40.96 to 24.131.40.96—1
9824.131.40.97/3224.131.40.97 to 24.131.40.97—1
9924.131.40.98/3224.131.40.98 to 24.131.40.98—1
10024.131.40.99/3224.131.40.99 to 24.131.40.99—1
10124.131.40.100/3224.131.40.100 to 24.131.40.100—1
10224.131.40.101/3224.131.40.101 to 24.131.40.101—1
10324.131.40.102/3224.131.40.102 to 24.131.40.102—1
10424.131.40.103/3224.131.40.103 to 24.131.40.103—1
10524.131.40.104/3224.131.40.104 to 24.131.40.104—1
10624.131.40.105/3224.131.40.105 to 24.131.40.105—1
10724.131.40.106/3224.131.40.106 to 24.131.40.106—1
10824.131.40.107/3224.131.40.107 to 24.131.40.107—1
10924.131.40.108/3224.131.40.108 to 24.131.40.108—1
11024.131.40.109/3224.131.40.109 to 24.131.40.109—1
11124.131.40.110/3224.131.40.110 to 24.131.40.110—1
11224.131.40.111/3224.131.40.111 to 24.131.40.111—1
11324.131.40.112/3224.131.40.112 to 24.131.40.112—1
11424.131.40.113/3224.131.40.113 to 24.131.40.113—1
11524.131.40.114/3224.131.40.114 to 24.131.40.114—1
11624.131.40.115/3224.131.40.115 to 24.131.40.115—1
11724.131.40.116/3224.131.40.116 to 24.131.40.116—1
11824.131.40.117/3224.131.40.117 to 24.131.40.117—1
11924.131.40.118/3224.131.40.118 to 24.131.40.118—1
12024.131.40.119/3224.131.40.119 to 24.131.40.119—1
12124.131.40.120/3224.131.40.120 to 24.131.40.120—1
12224.131.40.121/3224.131.40.121 to 24.131.40.121—1
12324.131.40.122/3224.131.40.122 to 24.131.40.122—1
12424.131.40.123/3224.131.40.123 to 24.131.40.123—1
12524.131.40.124/3224.131.40.124 to 24.131.40.124—1
12624.131.40.125/3224.131.40.125 to 24.131.40.125—1
12724.131.40.126/3224.131.40.126 to 24.131.40.126—1
12824.131.40.127/3224.131.40.127 to 24.131.40.127—1
12924.131.40.128/3224.131.40.128 to 24.131.40.128—1
13024.131.40.129/3224.131.40.129 to 24.131.40.129—1
13124.131.40.130/3224.131.40.130 to 24.131.40.130—1
13224.131.40.131/3224.131.40.131 to 24.131.40.131—1
13324.131.40.132/3224.131.40.132 to 24.131.40.132—1
13424.131.40.133/3224.131.40.133 to 24.131.40.133—1
13524.131.40.134/3224.131.40.134 to 24.131.40.134—1
13624.131.40.135/3224.131.40.135 to 24.131.40.135—1
13724.131.40.136/3224.131.40.136 to 24.131.40.136—1
13824.131.40.137/3224.131.40.137 to 24.131.40.137—1
13924.131.40.138/3224.131.40.138 to 24.131.40.138—1
14024.131.40.139/3224.131.40.139 to 24.131.40.139—1
14124.131.40.140/3224.131.40.140 to 24.131.40.140—1
14224.131.40.141/3224.131.40.141 to 24.131.40.141—1
14324.131.40.142/3224.131.40.142 to 24.131.40.142—1
14424.131.40.143/3224.131.40.143 to 24.131.40.143—1
14524.131.40.144/3224.131.40.144 to 24.131.40.144—1
14624.131.40.145/3224.131.40.145 to 24.131.40.145—1
14724.131.40.146/3224.131.40.146 to 24.131.40.146—1
14824.131.40.147/3224.131.40.147 to 24.131.40.147—1
14924.131.40.148/3224.131.40.148 to 24.131.40.148—1
15024.131.40.149/3224.131.40.149 to 24.131.40.149—1
15124.131.40.150/3224.131.40.150 to 24.131.40.150—1
15224.131.40.151/3224.131.40.151 to 24.131.40.151—1
15324.131.40.152/3224.131.40.152 to 24.131.40.152—1
15424.131.40.153/3224.131.40.153 to 24.131.40.153—1
15524.131.40.154/3224.131.40.154 to 24.131.40.154—1
15624.131.40.155/3224.131.40.155 to 24.131.40.155—1
15724.131.40.156/3224.131.40.156 to 24.131.40.156—1
15824.131.40.157/3224.131.40.157 to 24.131.40.157—1
15924.131.40.158/3224.131.40.158 to 24.131.40.158—1
16024.131.40.159/3224.131.40.159 to 24.131.40.159—1
16124.131.40.160/3224.131.40.160 to 24.131.40.160—1
16224.131.40.161/3224.131.40.161 to 24.131.40.161—1
16324.131.40.162/3224.131.40.162 to 24.131.40.162—1
16424.131.40.163/3224.131.40.163 to 24.131.40.163—1
16524.131.40.164/3224.131.40.164 to 24.131.40.164—1
16624.131.40.165/3224.131.40.165 to 24.131.40.165—1
16724.131.40.166/3224.131.40.166 to 24.131.40.166—1
16824.131.40.167/3224.131.40.167 to 24.131.40.167—1
16924.131.40.168/3224.131.40.168 to 24.131.40.168—1
17024.131.40.169/3224.131.40.169 to 24.131.40.169—1
17124.131.40.170/3224.131.40.170 to 24.131.40.170—1
17224.131.40.171/3224.131.40.171 to 24.131.40.171—1
17324.131.40.172/3224.131.40.172 to 24.131.40.172—1
17424.131.40.173/3224.131.40.173 to 24.131.40.173—1
17524.131.40.174/3224.131.40.174 to 24.131.40.174—1
17624.131.40.175/3224.131.40.175 to 24.131.40.175—1
17724.131.40.176/3224.131.40.176 to 24.131.40.176—1
17824.131.40.177/3224.131.40.177 to 24.131.40.177—1
17924.131.40.178/3224.131.40.178 to 24.131.40.178—1
18024.131.40.179/3224.131.40.179 to 24.131.40.179—1
18124.131.40.180/3224.131.40.180 to 24.131.40.180—1
18224.131.40.181/3224.131.40.181 to 24.131.40.181—1
18324.131.40.182/3224.131.40.182 to 24.131.40.182—1
18424.131.40.183/3224.131.40.183 to 24.131.40.183—1
18524.131.40.184/3224.131.40.184 to 24.131.40.184—1
18624.131.40.185/3224.131.40.185 to 24.131.40.185—1
18724.131.40.186/3224.131.40.186 to 24.131.40.186—1
18824.131.40.187/3224.131.40.187 to 24.131.40.187—1
18924.131.40.188/3224.131.40.188 to 24.131.40.188—1
19024.131.40.189/3224.131.40.189 to 24.131.40.189—1
19124.131.40.190/3224.131.40.190 to 24.131.40.190—1
19224.131.40.191/3224.131.40.191 to 24.131.40.191—1
19324.131.40.192/3224.131.40.192 to 24.131.40.192—1
19424.131.40.193/3224.131.40.193 to 24.131.40.193—1
19524.131.40.194/3224.131.40.194 to 24.131.40.194—1
19624.131.40.195/3224.131.40.195 to 24.131.40.195—1
19724.131.40.196/3224.131.40.196 to 24.131.40.196—1
19824.131.40.197/3224.131.40.197 to 24.131.40.197—1
19924.131.40.198/3224.131.40.198 to 24.131.40.198—1
20024.131.40.199/3224.131.40.199 to 24.131.40.199—1
20124.131.40.200/3224.131.40.200 to 24.131.40.200—1
20224.131.40.201/3224.131.40.201 to 24.131.40.201—1
20324.131.40.202/3224.131.40.202 to 24.131.40.202—1
20424.131.40.203/3224.131.40.203 to 24.131.40.203—1
20524.131.40.204/3224.131.40.204 to 24.131.40.204—1
20624.131.40.205/3224.131.40.205 to 24.131.40.205—1
20724.131.40.206/3224.131.40.206 to 24.131.40.206—1
20824.131.40.207/3224.131.40.207 to 24.131.40.207—1
20924.131.40.208/3224.131.40.208 to 24.131.40.208—1
21024.131.40.209/3224.131.40.209 to 24.131.40.209—1
21124.131.40.210/3224.131.40.210 to 24.131.40.210—1
21224.131.40.211/3224.131.40.211 to 24.131.40.211—1
21324.131.40.212/3224.131.40.212 to 24.131.40.212—1
21424.131.40.213/3224.131.40.213 to 24.131.40.213—1
21524.131.40.214/3224.131.40.214 to 24.131.40.214—1
21624.131.40.215/3224.131.40.215 to 24.131.40.215—1
21724.131.40.216/3224.131.40.216 to 24.131.40.216—1
21824.131.40.217/3224.131.40.217 to 24.131.40.217—1
21924.131.40.218/3224.131.40.218 to 24.131.40.218—1
22024.131.40.219/3224.131.40.219 to 24.131.40.219—1
22124.131.40.220/3224.131.40.220 to 24.131.40.220—1
22224.131.40.221/3224.131.40.221 to 24.131.40.221—1
22324.131.40.222/3224.131.40.222 to 24.131.40.222—1
22424.131.40.223/3224.131.40.223 to 24.131.40.223—1
22524.131.40.224/3224.131.40.224 to 24.131.40.224—1
22624.131.40.225/3224.131.40.225 to 24.131.40.225—1
22724.131.40.226/3224.131.40.226 to 24.131.40.226—1
22824.131.40.227/3224.131.40.227 to 24.131.40.227—1
22924.131.40.228/3224.131.40.228 to 24.131.40.228—1
23024.131.40.229/3224.131.40.229 to 24.131.40.229—1
23124.131.40.230/3224.131.40.230 to 24.131.40.230—1
23224.131.40.231/3224.131.40.231 to 24.131.40.231—1
23324.131.40.232/3224.131.40.232 to 24.131.40.232—1
23424.131.40.233/3224.131.40.233 to 24.131.40.233—1
23524.131.40.234/3224.131.40.234 to 24.131.40.234—1
23624.131.40.235/3224.131.40.235 to 24.131.40.235—1
23724.131.40.236/3224.131.40.236 to 24.131.40.236—1
23824.131.40.237/3224.131.40.237 to 24.131.40.237—1
23924.131.40.238/3224.131.40.238 to 24.131.40.238—1
24024.131.40.239/3224.131.40.239 to 24.131.40.239—1
24124.131.40.240/3224.131.40.240 to 24.131.40.240—1
24224.131.40.241/3224.131.40.241 to 24.131.40.241—1
24324.131.40.242/3224.131.40.242 to 24.131.40.242—1
24424.131.40.243/3224.131.40.243 to 24.131.40.243—1
24524.131.40.244/3224.131.40.244 to 24.131.40.244—1
24624.131.40.245/3224.131.40.245 to 24.131.40.245—1
24724.131.40.246/3224.131.40.246 to 24.131.40.246—1
24824.131.40.247/3224.131.40.247 to 24.131.40.247—1
24924.131.40.248/3224.131.40.248 to 24.131.40.248—1
25024.131.40.249/3224.131.40.249 to 24.131.40.249—1
25124.131.40.250/3224.131.40.250 to 24.131.40.250—1
25224.131.40.251/3224.131.40.251 to 24.131.40.251—1
25324.131.40.252/3224.131.40.252 to 24.131.40.252—1
25424.131.40.253/3224.131.40.253 to 24.131.40.253—1
25524.131.40.254/3224.131.40.254 to 24.131.40.254—1
25624.131.40.255/3224.131.40.255 to 24.131.40.255—1

IPv4 CIDR reference (/0 to /32)

IPv4 prefix lengths
PrefixSubnet maskWildcardAddressesUsable hostsSizeTypical use
/00.0.0.0255.255.255.2554,294,967,2964,294,967,29416,777,216 × /24
/1128.0.0.0127.255.255.2552,147,483,6482,147,483,6468,388,608 × /24
/2192.0.0.063.255.255.2551,073,741,8241,073,741,8224,194,304 × /24
/3224.0.0.031.255.255.255536,870,912536,870,9102,097,152 × /24
/4240.0.0.015.255.255.255268,435,456268,435,4541,048,576 × /24
/5248.0.0.07.255.255.255134,217,728134,217,726524,288 × /24
/6252.0.0.03.255.255.25567,108,86467,108,862262,144 × /24
/7254.0.0.01.255.255.25533,554,43233,554,430131,072 × /24
/8255.0.0.00.255.255.25516,777,21616,777,21465,536 × /24Old class A; 10.0.0.0/8
/9255.128.0.00.127.255.2558,388,6088,388,60632,768 × /24
/10255.192.0.00.63.255.2554,194,3044,194,30216,384 × /24
/11255.224.0.00.31.255.2552,097,1522,097,1508,192 × /24
/12255.240.0.00.15.255.2551,048,5761,048,5744,096 × /24172.16.0.0/12
/13255.248.0.00.7.255.255524,288524,2862,048 × /24
/14255.252.0.00.3.255.255262,144262,1421,024 × /24
/15255.254.0.00.1.255.255131,072131,070512 × /24
/16255.255.0.00.0.255.25565,53665,534256 × /24Old class B; 192.168.0.0/16
/17255.255.128.00.0.127.25532,76832,766128 × /24
/18255.255.192.00.0.63.25516,38416,38264 × /24
/19255.255.224.00.0.31.2558,1928,19032 × /24
/20255.255.240.00.0.15.2554,0964,09416 × /24
/21255.255.248.00.0.7.2552,0482,0468 × /24
/22255.255.252.00.0.3.2551,0241,0224 × /24Large office or guest Wi-Fi (1,022 hosts)
/23255.255.254.00.0.1.2555125102 × /24Larger office LAN (510 hosts)
/24255.255.255.00.0.0.2552562541 × /24Typical office LAN (old class C)
/25255.255.255.1280.0.0.1271281261/2 of a /24Smaller LAN or VLAN
/26255.255.255.1920.0.0.6364621/4 of a /24Smaller LAN or VLAN
/27255.255.255.2240.0.0.3132301/8 of a /24Small VLAN, phones, cameras
/28255.255.255.2400.0.0.1516141/16 of a /24Small VLAN, phones, cameras
/29255.255.255.2480.0.0.7861/32 of a /24Small fixed public block (5 usable)
/30255.255.255.2520.0.0.3421/64 of a /24Point-to-point (old style)
/31255.255.255.2540.0.0.1221/128 of a /24Point-to-point link (RFC 3021)
/32255.255.255.2550.0.0.0111/256 of a /24One host

IPv6 prefix reference

IPv6 prefix lengths
PrefixAddresses/64 LANs/48 sitesNibbleTypical use
/342,535,295,865,117,307,932,921,825,928,971,026,432 (2^125)2,305,843,009,213,693,95235,184,372,088,832NoAll global unicast (2000::/3)
/165,192,296,858,534,827,628,530,496,329,220,096 (2^112)281,474,976,710,6564,294,967,296Yes
/20324,518,553,658,426,726,783,156,020,576,256 (2^108)17,592,186,044,416268,435,456YesLarge provider allocation (RIPE minimum for some)
/29633,825,300,114,114,700,748,351,602,688 (2^99)34,359,738,368524,288NoRIPE allocation to a provider (often)
/3279,228,162,514,264,337,593,543,950,336 (2^96)4,294,967,29665,536YesProvider allocation (RIPE default)
/364,951,760,157,141,521,099,596,496,896 (2^92)268,435,4564,096Yes
/40309,485,009,821,345,068,724,781,056 (2^88)16,777,216256Yes
/4419,342,813,113,834,066,795,298,816 (2^84)1,048,57616Yes
/481,208,925,819,614,629,174,706,176 (2^80)65,5361YesOne site or organisation (RIPE PI / assignment)
/5275,557,863,725,914,323,419,136 (2^76)4,096Yes
/564,722,366,482,869,645,213,696 (2^72)256YesSmall site or home (common provider assignment)
/60295,147,905,179,352,825,856 (2^68)16YesSome home broadband (16 LANs)
/6418,446,744,073,709,551,616 (2^64)1YesOne LAN or VLAN (needed for SLAAC)
/7272,057,594,037,927,936 (2^56)1/256 of a /64Yes
/80281,474,976,710,656 (2^48)1/65,536 of a /64Yes
/964,294,967,2961/4,294,967,296 of a /64YesEmbeds an IPv4 address (NAT64)
/11265,5361/281,474,976,710,656 of a /64Yes
/1202561/72,057,594,037,927,936 of a /64Yes
/124161/1,152,921,504,606,846,976 of a /64Yes
/12641/4,611,686,018,427,387,904 of a /64No
/12721/9,223,372,036,854,775,808 of a /64NoPoint-to-point link (RFC 6164)
/12811/18,446,744,073,709,551,616 of a /64YesOne host or loopback

Private and special ranges

IPv4

Special-purpose ranges
RangeNameWhat it is
255.255.255.255/32Limited broadcastEvery host on the local network
0.0.0.0/8This networkNot routed; 0.0.0.0 means "any address" in settings
10.0.0.0/8Private (RFC 1918)Office and home networks; not routed on the internet
100.64.0.0/10Shared address space (CGNAT)Used by providers behind carrier-grade NAT (RFC 6598)
127.0.0.0/8LoopbackThis computer
169.254.0.0/16Link-local (APIPA)Self-assigned when no DHCP server answers
172.16.0.0/12Private (RFC 1918)Office and home networks; not routed on the internet
192.0.0.0/24IETF protocol assignmentsSpecial uses such as DS-Lite
192.0.2.0/24Documentation (TEST-NET-1)For examples; never used on a network
192.88.99.0/246to4 relay (deprecated)Formerly anycast for 6to4
192.168.0.0/16Private (RFC 1918)Office and home networks; not routed on the internet
198.18.0.0/15BenchmarkingNetwork equipment testing (RFC 2544)
198.51.100.0/24Documentation (TEST-NET-2)For examples; never used on a network
203.0.113.0/24Documentation (TEST-NET-3)For examples; never used on a network
224.0.0.0/4MulticastOne-to-many traffic, such as IPTV and routing protocols
240.0.0.0/4ReservedFuture use; not usable on most systems

IPv6

Special-purpose ranges
RangeNameWhat it is
::/128UnspecifiedNo address; :: means "any address" in settings
::1/128LoopbackThis computer
::ffff:0:0/96IPv4-mappedAn IPv4 address written as IPv6
64:ff9b::/96NAT64IPv4 addresses reached through a NAT64 gateway
100::/64Discard onlyTraffic sent here is dropped (RFC 6666)
2001:db8::/32DocumentationFor examples; never used on a network
2001::/32TeredoIPv6 tunnelled over IPv4 UDP
2002::/166to4IPv6 tunnelled over IPv4 (largely retired)
3fff::/20DocumentationFor examples (RFC 9637)
fc00::/7Unique local (ULA)Private IPv6, like RFC 1918; usually fd00::/8
fe80::/10Link-localEvery IPv6 interface has one; not routed
ff00::/8MulticastOne-to-many traffic; replaces broadcast
2000::/3Global unicastPublic internet addresses

About this tool

A network is written as an address and a prefix length, such as 192.168.1.0/24: the first 24 bits name the network and the rest number the devices on it. The calculator works out where the network starts and ends, how many devices it holds, its subnet and wildcard masks, and the reverse DNS zone to ask your provider for.

It also splits a network into equal smaller ones (one per VLAN or site), turns a range of addresses into the fewest CIDR blocks for a firewall rule, and lists every IPv4 prefix length and the common IPv6 ones in reference tables.

Common questions

Why are two addresses lost in every IPv4 subnet?

The first address names the network and the last is the broadcast address, so a /24 has 256 addresses but 254 for devices. A /31 (a link between two routers) and a /32 (one host) are the exceptions.

What size of IPv6 network should a LAN use?

Always /64. Devices pick their own address within it (SLAAC), which needs the full 64 bits. A site usually gets a /48 or /56 from its provider, which holds 65,536 or 256 LANs.

What is a wildcard mask?

The subnet mask turned inside out: 255.255.255.0 becomes 0.0.0.255. Cisco access lists and OSPF use it to say which bits must match.

Which ranges can I use inside an office?

IPv4: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. IPv6: unique local addresses from fd00::/8, though most networks use the public prefix from their provider.