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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.

Network123.131.0.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
123.131.0.0
Broadcast address
123.131.15.255
First usable
123.131.0.1
Last usable
123.131.15.254
Usable hosts
4,094 (4,096 less the network and broadcast addresses)
Subnet mask
255.255.240.0
Wildcard mask
0.0.15.255 (Cisco ACLs, OSPF)
Prefix length
/20
Type
Public public
Old class
A (default /8)
As numbers
Hex 7B830000 · Integer 2072182784 to 2072186879
Reverse DNS zones
0.131.123.in-addr.arpa
1.131.123.in-addr.arpa
2.131.123.in-addr.arpa
3.131.123.in-addr.arpa
4.131.123.in-addr.arpa
5.131.123.in-addr.arpa
6.131.123.in-addr.arpa
7.131.123.in-addr.arpa
8.131.123.in-addr.arpa
9.131.123.in-addr.arpa
10.131.123.in-addr.arpa
11.131.123.in-addr.arpa
12.131.123.in-addr.arpa
13.131.123.in-addr.arpa
14.131.123.in-addr.arpa
15.131.123.in-addr.arpa
/20 is not on a 8-bit boundary, so it takes 16 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01111011.10000011.00000000.00000000123.131.0.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network01111011.10000011.00000000.00000000123.131.0.0
Broadcast01111011.10000011.00001111.11111111123.131.15.255
Split into smaller subnets/32
/21 (2)/22 (4)/23 (8)/24 (16)/25 (32)/26 (64)/27 (128)/28 (256)/29 (512)/30 (1,024)/31 (2,048)/32 (4,096)

123.131.0.0/20 makes 4,096 subnets of /32; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1123.131.0.0/32123.131.0.0 to 123.131.0.0—1
2123.131.0.1/32123.131.0.1 to 123.131.0.1—1
3123.131.0.2/32123.131.0.2 to 123.131.0.2—1
4123.131.0.3/32123.131.0.3 to 123.131.0.3—1
5123.131.0.4/32123.131.0.4 to 123.131.0.4—1
6123.131.0.5/32123.131.0.5 to 123.131.0.5—1
7123.131.0.6/32123.131.0.6 to 123.131.0.6—1
8123.131.0.7/32123.131.0.7 to 123.131.0.7—1
9123.131.0.8/32123.131.0.8 to 123.131.0.8—1
10123.131.0.9/32123.131.0.9 to 123.131.0.9—1
11123.131.0.10/32123.131.0.10 to 123.131.0.10—1
12123.131.0.11/32123.131.0.11 to 123.131.0.11—1
13123.131.0.12/32123.131.0.12 to 123.131.0.12—1
14123.131.0.13/32123.131.0.13 to 123.131.0.13—1
15123.131.0.14/32123.131.0.14 to 123.131.0.14—1
16123.131.0.15/32123.131.0.15 to 123.131.0.15—1
17123.131.0.16/32123.131.0.16 to 123.131.0.16—1
18123.131.0.17/32123.131.0.17 to 123.131.0.17—1
19123.131.0.18/32123.131.0.18 to 123.131.0.18—1
20123.131.0.19/32123.131.0.19 to 123.131.0.19—1
21123.131.0.20/32123.131.0.20 to 123.131.0.20—1
22123.131.0.21/32123.131.0.21 to 123.131.0.21—1
23123.131.0.22/32123.131.0.22 to 123.131.0.22—1
24123.131.0.23/32123.131.0.23 to 123.131.0.23—1
25123.131.0.24/32123.131.0.24 to 123.131.0.24—1
26123.131.0.25/32123.131.0.25 to 123.131.0.25—1
27123.131.0.26/32123.131.0.26 to 123.131.0.26—1
28123.131.0.27/32123.131.0.27 to 123.131.0.27—1
29123.131.0.28/32123.131.0.28 to 123.131.0.28—1
30123.131.0.29/32123.131.0.29 to 123.131.0.29—1
31123.131.0.30/32123.131.0.30 to 123.131.0.30—1
32123.131.0.31/32123.131.0.31 to 123.131.0.31—1
33123.131.0.32/32123.131.0.32 to 123.131.0.32—1
34123.131.0.33/32123.131.0.33 to 123.131.0.33—1
35123.131.0.34/32123.131.0.34 to 123.131.0.34—1
36123.131.0.35/32123.131.0.35 to 123.131.0.35—1
37123.131.0.36/32123.131.0.36 to 123.131.0.36—1
38123.131.0.37/32123.131.0.37 to 123.131.0.37—1
39123.131.0.38/32123.131.0.38 to 123.131.0.38—1
40123.131.0.39/32123.131.0.39 to 123.131.0.39—1
41123.131.0.40/32123.131.0.40 to 123.131.0.40—1
42123.131.0.41/32123.131.0.41 to 123.131.0.41—1
43123.131.0.42/32123.131.0.42 to 123.131.0.42—1
44123.131.0.43/32123.131.0.43 to 123.131.0.43—1
45123.131.0.44/32123.131.0.44 to 123.131.0.44—1
46123.131.0.45/32123.131.0.45 to 123.131.0.45—1
47123.131.0.46/32123.131.0.46 to 123.131.0.46—1
48123.131.0.47/32123.131.0.47 to 123.131.0.47—1
49123.131.0.48/32123.131.0.48 to 123.131.0.48—1
50123.131.0.49/32123.131.0.49 to 123.131.0.49—1
51123.131.0.50/32123.131.0.50 to 123.131.0.50—1
52123.131.0.51/32123.131.0.51 to 123.131.0.51—1
53123.131.0.52/32123.131.0.52 to 123.131.0.52—1
54123.131.0.53/32123.131.0.53 to 123.131.0.53—1
55123.131.0.54/32123.131.0.54 to 123.131.0.54—1
56123.131.0.55/32123.131.0.55 to 123.131.0.55—1
57123.131.0.56/32123.131.0.56 to 123.131.0.56—1
58123.131.0.57/32123.131.0.57 to 123.131.0.57—1
59123.131.0.58/32123.131.0.58 to 123.131.0.58—1
60123.131.0.59/32123.131.0.59 to 123.131.0.59—1
61123.131.0.60/32123.131.0.60 to 123.131.0.60—1
62123.131.0.61/32123.131.0.61 to 123.131.0.61—1
63123.131.0.62/32123.131.0.62 to 123.131.0.62—1
64123.131.0.63/32123.131.0.63 to 123.131.0.63—1
65123.131.0.64/32123.131.0.64 to 123.131.0.64—1
66123.131.0.65/32123.131.0.65 to 123.131.0.65—1
67123.131.0.66/32123.131.0.66 to 123.131.0.66—1
68123.131.0.67/32123.131.0.67 to 123.131.0.67—1
69123.131.0.68/32123.131.0.68 to 123.131.0.68—1
70123.131.0.69/32123.131.0.69 to 123.131.0.69—1
71123.131.0.70/32123.131.0.70 to 123.131.0.70—1
72123.131.0.71/32123.131.0.71 to 123.131.0.71—1
73123.131.0.72/32123.131.0.72 to 123.131.0.72—1
74123.131.0.73/32123.131.0.73 to 123.131.0.73—1
75123.131.0.74/32123.131.0.74 to 123.131.0.74—1
76123.131.0.75/32123.131.0.75 to 123.131.0.75—1
77123.131.0.76/32123.131.0.76 to 123.131.0.76—1
78123.131.0.77/32123.131.0.77 to 123.131.0.77—1
79123.131.0.78/32123.131.0.78 to 123.131.0.78—1
80123.131.0.79/32123.131.0.79 to 123.131.0.79—1
81123.131.0.80/32123.131.0.80 to 123.131.0.80—1
82123.131.0.81/32123.131.0.81 to 123.131.0.81—1
83123.131.0.82/32123.131.0.82 to 123.131.0.82—1
84123.131.0.83/32123.131.0.83 to 123.131.0.83—1
85123.131.0.84/32123.131.0.84 to 123.131.0.84—1
86123.131.0.85/32123.131.0.85 to 123.131.0.85—1
87123.131.0.86/32123.131.0.86 to 123.131.0.86—1
88123.131.0.87/32123.131.0.87 to 123.131.0.87—1
89123.131.0.88/32123.131.0.88 to 123.131.0.88—1
90123.131.0.89/32123.131.0.89 to 123.131.0.89—1
91123.131.0.90/32123.131.0.90 to 123.131.0.90—1
92123.131.0.91/32123.131.0.91 to 123.131.0.91—1
93123.131.0.92/32123.131.0.92 to 123.131.0.92—1
94123.131.0.93/32123.131.0.93 to 123.131.0.93—1
95123.131.0.94/32123.131.0.94 to 123.131.0.94—1
96123.131.0.95/32123.131.0.95 to 123.131.0.95—1
97123.131.0.96/32123.131.0.96 to 123.131.0.96—1
98123.131.0.97/32123.131.0.97 to 123.131.0.97—1
99123.131.0.98/32123.131.0.98 to 123.131.0.98—1
100123.131.0.99/32123.131.0.99 to 123.131.0.99—1
101123.131.0.100/32123.131.0.100 to 123.131.0.100—1
102123.131.0.101/32123.131.0.101 to 123.131.0.101—1
103123.131.0.102/32123.131.0.102 to 123.131.0.102—1
104123.131.0.103/32123.131.0.103 to 123.131.0.103—1
105123.131.0.104/32123.131.0.104 to 123.131.0.104—1
106123.131.0.105/32123.131.0.105 to 123.131.0.105—1
107123.131.0.106/32123.131.0.106 to 123.131.0.106—1
108123.131.0.107/32123.131.0.107 to 123.131.0.107—1
109123.131.0.108/32123.131.0.108 to 123.131.0.108—1
110123.131.0.109/32123.131.0.109 to 123.131.0.109—1
111123.131.0.110/32123.131.0.110 to 123.131.0.110—1
112123.131.0.111/32123.131.0.111 to 123.131.0.111—1
113123.131.0.112/32123.131.0.112 to 123.131.0.112—1
114123.131.0.113/32123.131.0.113 to 123.131.0.113—1
115123.131.0.114/32123.131.0.114 to 123.131.0.114—1
116123.131.0.115/32123.131.0.115 to 123.131.0.115—1
117123.131.0.116/32123.131.0.116 to 123.131.0.116—1
118123.131.0.117/32123.131.0.117 to 123.131.0.117—1
119123.131.0.118/32123.131.0.118 to 123.131.0.118—1
120123.131.0.119/32123.131.0.119 to 123.131.0.119—1
121123.131.0.120/32123.131.0.120 to 123.131.0.120—1
122123.131.0.121/32123.131.0.121 to 123.131.0.121—1
123123.131.0.122/32123.131.0.122 to 123.131.0.122—1
124123.131.0.123/32123.131.0.123 to 123.131.0.123—1
125123.131.0.124/32123.131.0.124 to 123.131.0.124—1
126123.131.0.125/32123.131.0.125 to 123.131.0.125—1
127123.131.0.126/32123.131.0.126 to 123.131.0.126—1
128123.131.0.127/32123.131.0.127 to 123.131.0.127—1
129123.131.0.128/32123.131.0.128 to 123.131.0.128—1
130123.131.0.129/32123.131.0.129 to 123.131.0.129—1
131123.131.0.130/32123.131.0.130 to 123.131.0.130—1
132123.131.0.131/32123.131.0.131 to 123.131.0.131—1
133123.131.0.132/32123.131.0.132 to 123.131.0.132—1
134123.131.0.133/32123.131.0.133 to 123.131.0.133—1
135123.131.0.134/32123.131.0.134 to 123.131.0.134—1
136123.131.0.135/32123.131.0.135 to 123.131.0.135—1
137123.131.0.136/32123.131.0.136 to 123.131.0.136—1
138123.131.0.137/32123.131.0.137 to 123.131.0.137—1
139123.131.0.138/32123.131.0.138 to 123.131.0.138—1
140123.131.0.139/32123.131.0.139 to 123.131.0.139—1
141123.131.0.140/32123.131.0.140 to 123.131.0.140—1
142123.131.0.141/32123.131.0.141 to 123.131.0.141—1
143123.131.0.142/32123.131.0.142 to 123.131.0.142—1
144123.131.0.143/32123.131.0.143 to 123.131.0.143—1
145123.131.0.144/32123.131.0.144 to 123.131.0.144—1
146123.131.0.145/32123.131.0.145 to 123.131.0.145—1
147123.131.0.146/32123.131.0.146 to 123.131.0.146—1
148123.131.0.147/32123.131.0.147 to 123.131.0.147—1
149123.131.0.148/32123.131.0.148 to 123.131.0.148—1
150123.131.0.149/32123.131.0.149 to 123.131.0.149—1
151123.131.0.150/32123.131.0.150 to 123.131.0.150—1
152123.131.0.151/32123.131.0.151 to 123.131.0.151—1
153123.131.0.152/32123.131.0.152 to 123.131.0.152—1
154123.131.0.153/32123.131.0.153 to 123.131.0.153—1
155123.131.0.154/32123.131.0.154 to 123.131.0.154—1
156123.131.0.155/32123.131.0.155 to 123.131.0.155—1
157123.131.0.156/32123.131.0.156 to 123.131.0.156—1
158123.131.0.157/32123.131.0.157 to 123.131.0.157—1
159123.131.0.158/32123.131.0.158 to 123.131.0.158—1
160123.131.0.159/32123.131.0.159 to 123.131.0.159—1
161123.131.0.160/32123.131.0.160 to 123.131.0.160—1
162123.131.0.161/32123.131.0.161 to 123.131.0.161—1
163123.131.0.162/32123.131.0.162 to 123.131.0.162—1
164123.131.0.163/32123.131.0.163 to 123.131.0.163—1
165123.131.0.164/32123.131.0.164 to 123.131.0.164—1
166123.131.0.165/32123.131.0.165 to 123.131.0.165—1
167123.131.0.166/32123.131.0.166 to 123.131.0.166—1
168123.131.0.167/32123.131.0.167 to 123.131.0.167—1
169123.131.0.168/32123.131.0.168 to 123.131.0.168—1
170123.131.0.169/32123.131.0.169 to 123.131.0.169—1
171123.131.0.170/32123.131.0.170 to 123.131.0.170—1
172123.131.0.171/32123.131.0.171 to 123.131.0.171—1
173123.131.0.172/32123.131.0.172 to 123.131.0.172—1
174123.131.0.173/32123.131.0.173 to 123.131.0.173—1
175123.131.0.174/32123.131.0.174 to 123.131.0.174—1
176123.131.0.175/32123.131.0.175 to 123.131.0.175—1
177123.131.0.176/32123.131.0.176 to 123.131.0.176—1
178123.131.0.177/32123.131.0.177 to 123.131.0.177—1
179123.131.0.178/32123.131.0.178 to 123.131.0.178—1
180123.131.0.179/32123.131.0.179 to 123.131.0.179—1
181123.131.0.180/32123.131.0.180 to 123.131.0.180—1
182123.131.0.181/32123.131.0.181 to 123.131.0.181—1
183123.131.0.182/32123.131.0.182 to 123.131.0.182—1
184123.131.0.183/32123.131.0.183 to 123.131.0.183—1
185123.131.0.184/32123.131.0.184 to 123.131.0.184—1
186123.131.0.185/32123.131.0.185 to 123.131.0.185—1
187123.131.0.186/32123.131.0.186 to 123.131.0.186—1
188123.131.0.187/32123.131.0.187 to 123.131.0.187—1
189123.131.0.188/32123.131.0.188 to 123.131.0.188—1
190123.131.0.189/32123.131.0.189 to 123.131.0.189—1
191123.131.0.190/32123.131.0.190 to 123.131.0.190—1
192123.131.0.191/32123.131.0.191 to 123.131.0.191—1
193123.131.0.192/32123.131.0.192 to 123.131.0.192—1
194123.131.0.193/32123.131.0.193 to 123.131.0.193—1
195123.131.0.194/32123.131.0.194 to 123.131.0.194—1
196123.131.0.195/32123.131.0.195 to 123.131.0.195—1
197123.131.0.196/32123.131.0.196 to 123.131.0.196—1
198123.131.0.197/32123.131.0.197 to 123.131.0.197—1
199123.131.0.198/32123.131.0.198 to 123.131.0.198—1
200123.131.0.199/32123.131.0.199 to 123.131.0.199—1
201123.131.0.200/32123.131.0.200 to 123.131.0.200—1
202123.131.0.201/32123.131.0.201 to 123.131.0.201—1
203123.131.0.202/32123.131.0.202 to 123.131.0.202—1
204123.131.0.203/32123.131.0.203 to 123.131.0.203—1
205123.131.0.204/32123.131.0.204 to 123.131.0.204—1
206123.131.0.205/32123.131.0.205 to 123.131.0.205—1
207123.131.0.206/32123.131.0.206 to 123.131.0.206—1
208123.131.0.207/32123.131.0.207 to 123.131.0.207—1
209123.131.0.208/32123.131.0.208 to 123.131.0.208—1
210123.131.0.209/32123.131.0.209 to 123.131.0.209—1
211123.131.0.210/32123.131.0.210 to 123.131.0.210—1
212123.131.0.211/32123.131.0.211 to 123.131.0.211—1
213123.131.0.212/32123.131.0.212 to 123.131.0.212—1
214123.131.0.213/32123.131.0.213 to 123.131.0.213—1
215123.131.0.214/32123.131.0.214 to 123.131.0.214—1
216123.131.0.215/32123.131.0.215 to 123.131.0.215—1
217123.131.0.216/32123.131.0.216 to 123.131.0.216—1
218123.131.0.217/32123.131.0.217 to 123.131.0.217—1
219123.131.0.218/32123.131.0.218 to 123.131.0.218—1
220123.131.0.219/32123.131.0.219 to 123.131.0.219—1
221123.131.0.220/32123.131.0.220 to 123.131.0.220—1
222123.131.0.221/32123.131.0.221 to 123.131.0.221—1
223123.131.0.222/32123.131.0.222 to 123.131.0.222—1
224123.131.0.223/32123.131.0.223 to 123.131.0.223—1
225123.131.0.224/32123.131.0.224 to 123.131.0.224—1
226123.131.0.225/32123.131.0.225 to 123.131.0.225—1
227123.131.0.226/32123.131.0.226 to 123.131.0.226—1
228123.131.0.227/32123.131.0.227 to 123.131.0.227—1
229123.131.0.228/32123.131.0.228 to 123.131.0.228—1
230123.131.0.229/32123.131.0.229 to 123.131.0.229—1
231123.131.0.230/32123.131.0.230 to 123.131.0.230—1
232123.131.0.231/32123.131.0.231 to 123.131.0.231—1
233123.131.0.232/32123.131.0.232 to 123.131.0.232—1
234123.131.0.233/32123.131.0.233 to 123.131.0.233—1
235123.131.0.234/32123.131.0.234 to 123.131.0.234—1
236123.131.0.235/32123.131.0.235 to 123.131.0.235—1
237123.131.0.236/32123.131.0.236 to 123.131.0.236—1
238123.131.0.237/32123.131.0.237 to 123.131.0.237—1
239123.131.0.238/32123.131.0.238 to 123.131.0.238—1
240123.131.0.239/32123.131.0.239 to 123.131.0.239—1
241123.131.0.240/32123.131.0.240 to 123.131.0.240—1
242123.131.0.241/32123.131.0.241 to 123.131.0.241—1
243123.131.0.242/32123.131.0.242 to 123.131.0.242—1
244123.131.0.243/32123.131.0.243 to 123.131.0.243—1
245123.131.0.244/32123.131.0.244 to 123.131.0.244—1
246123.131.0.245/32123.131.0.245 to 123.131.0.245—1
247123.131.0.246/32123.131.0.246 to 123.131.0.246—1
248123.131.0.247/32123.131.0.247 to 123.131.0.247—1
249123.131.0.248/32123.131.0.248 to 123.131.0.248—1
250123.131.0.249/32123.131.0.249 to 123.131.0.249—1
251123.131.0.250/32123.131.0.250 to 123.131.0.250—1
252123.131.0.251/32123.131.0.251 to 123.131.0.251—1
253123.131.0.252/32123.131.0.252 to 123.131.0.252—1
254123.131.0.253/32123.131.0.253 to 123.131.0.253—1
255123.131.0.254/32123.131.0.254 to 123.131.0.254—1
256123.131.0.255/32123.131.0.255 to 123.131.0.255—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.