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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.

Network181.2.32.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
181.2.32.0
Broadcast address
181.2.47.255
First usable
181.2.32.1
Last usable
181.2.47.254
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
B (default /16)
As numbers
Hex B5022000 · Integer 3036815360 to 3036819455
Reverse DNS zones
32.2.181.in-addr.arpa
33.2.181.in-addr.arpa
34.2.181.in-addr.arpa
35.2.181.in-addr.arpa
36.2.181.in-addr.arpa
37.2.181.in-addr.arpa
38.2.181.in-addr.arpa
39.2.181.in-addr.arpa
40.2.181.in-addr.arpa
41.2.181.in-addr.arpa
42.2.181.in-addr.arpa
43.2.181.in-addr.arpa
44.2.181.in-addr.arpa
45.2.181.in-addr.arpa
46.2.181.in-addr.arpa
47.2.181.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
Address10110101.00000010.00100000.00000000181.2.32.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network10110101.00000010.00100000.00000000181.2.32.0
Broadcast10110101.00000010.00101111.11111111181.2.47.255
Split into smaller subnets/31
/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)

181.2.32.0/20 makes 2,048 subnets of /31; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1181.2.32.0/31181.2.32.0 to 181.2.32.1—2
2181.2.32.2/31181.2.32.2 to 181.2.32.3—2
3181.2.32.4/31181.2.32.4 to 181.2.32.5—2
4181.2.32.6/31181.2.32.6 to 181.2.32.7—2
5181.2.32.8/31181.2.32.8 to 181.2.32.9—2
6181.2.32.10/31181.2.32.10 to 181.2.32.11—2
7181.2.32.12/31181.2.32.12 to 181.2.32.13—2
8181.2.32.14/31181.2.32.14 to 181.2.32.15—2
9181.2.32.16/31181.2.32.16 to 181.2.32.17—2
10181.2.32.18/31181.2.32.18 to 181.2.32.19—2
11181.2.32.20/31181.2.32.20 to 181.2.32.21—2
12181.2.32.22/31181.2.32.22 to 181.2.32.23—2
13181.2.32.24/31181.2.32.24 to 181.2.32.25—2
14181.2.32.26/31181.2.32.26 to 181.2.32.27—2
15181.2.32.28/31181.2.32.28 to 181.2.32.29—2
16181.2.32.30/31181.2.32.30 to 181.2.32.31—2
17181.2.32.32/31181.2.32.32 to 181.2.32.33—2
18181.2.32.34/31181.2.32.34 to 181.2.32.35—2
19181.2.32.36/31181.2.32.36 to 181.2.32.37—2
20181.2.32.38/31181.2.32.38 to 181.2.32.39—2
21181.2.32.40/31181.2.32.40 to 181.2.32.41—2
22181.2.32.42/31181.2.32.42 to 181.2.32.43—2
23181.2.32.44/31181.2.32.44 to 181.2.32.45—2
24181.2.32.46/31181.2.32.46 to 181.2.32.47—2
25181.2.32.48/31181.2.32.48 to 181.2.32.49—2
26181.2.32.50/31181.2.32.50 to 181.2.32.51—2
27181.2.32.52/31181.2.32.52 to 181.2.32.53—2
28181.2.32.54/31181.2.32.54 to 181.2.32.55—2
29181.2.32.56/31181.2.32.56 to 181.2.32.57—2
30181.2.32.58/31181.2.32.58 to 181.2.32.59—2
31181.2.32.60/31181.2.32.60 to 181.2.32.61—2
32181.2.32.62/31181.2.32.62 to 181.2.32.63—2
33181.2.32.64/31181.2.32.64 to 181.2.32.65—2
34181.2.32.66/31181.2.32.66 to 181.2.32.67—2
35181.2.32.68/31181.2.32.68 to 181.2.32.69—2
36181.2.32.70/31181.2.32.70 to 181.2.32.71—2
37181.2.32.72/31181.2.32.72 to 181.2.32.73—2
38181.2.32.74/31181.2.32.74 to 181.2.32.75—2
39181.2.32.76/31181.2.32.76 to 181.2.32.77—2
40181.2.32.78/31181.2.32.78 to 181.2.32.79—2
41181.2.32.80/31181.2.32.80 to 181.2.32.81—2
42181.2.32.82/31181.2.32.82 to 181.2.32.83—2
43181.2.32.84/31181.2.32.84 to 181.2.32.85—2
44181.2.32.86/31181.2.32.86 to 181.2.32.87—2
45181.2.32.88/31181.2.32.88 to 181.2.32.89—2
46181.2.32.90/31181.2.32.90 to 181.2.32.91—2
47181.2.32.92/31181.2.32.92 to 181.2.32.93—2
48181.2.32.94/31181.2.32.94 to 181.2.32.95—2
49181.2.32.96/31181.2.32.96 to 181.2.32.97—2
50181.2.32.98/31181.2.32.98 to 181.2.32.99—2
51181.2.32.100/31181.2.32.100 to 181.2.32.101—2
52181.2.32.102/31181.2.32.102 to 181.2.32.103—2
53181.2.32.104/31181.2.32.104 to 181.2.32.105—2
54181.2.32.106/31181.2.32.106 to 181.2.32.107—2
55181.2.32.108/31181.2.32.108 to 181.2.32.109—2
56181.2.32.110/31181.2.32.110 to 181.2.32.111—2
57181.2.32.112/31181.2.32.112 to 181.2.32.113—2
58181.2.32.114/31181.2.32.114 to 181.2.32.115—2
59181.2.32.116/31181.2.32.116 to 181.2.32.117—2
60181.2.32.118/31181.2.32.118 to 181.2.32.119—2
61181.2.32.120/31181.2.32.120 to 181.2.32.121—2
62181.2.32.122/31181.2.32.122 to 181.2.32.123—2
63181.2.32.124/31181.2.32.124 to 181.2.32.125—2
64181.2.32.126/31181.2.32.126 to 181.2.32.127—2
65181.2.32.128/31181.2.32.128 to 181.2.32.129—2
66181.2.32.130/31181.2.32.130 to 181.2.32.131—2
67181.2.32.132/31181.2.32.132 to 181.2.32.133—2
68181.2.32.134/31181.2.32.134 to 181.2.32.135—2
69181.2.32.136/31181.2.32.136 to 181.2.32.137—2
70181.2.32.138/31181.2.32.138 to 181.2.32.139—2
71181.2.32.140/31181.2.32.140 to 181.2.32.141—2
72181.2.32.142/31181.2.32.142 to 181.2.32.143—2
73181.2.32.144/31181.2.32.144 to 181.2.32.145—2
74181.2.32.146/31181.2.32.146 to 181.2.32.147—2
75181.2.32.148/31181.2.32.148 to 181.2.32.149—2
76181.2.32.150/31181.2.32.150 to 181.2.32.151—2
77181.2.32.152/31181.2.32.152 to 181.2.32.153—2
78181.2.32.154/31181.2.32.154 to 181.2.32.155—2
79181.2.32.156/31181.2.32.156 to 181.2.32.157—2
80181.2.32.158/31181.2.32.158 to 181.2.32.159—2
81181.2.32.160/31181.2.32.160 to 181.2.32.161—2
82181.2.32.162/31181.2.32.162 to 181.2.32.163—2
83181.2.32.164/31181.2.32.164 to 181.2.32.165—2
84181.2.32.166/31181.2.32.166 to 181.2.32.167—2
85181.2.32.168/31181.2.32.168 to 181.2.32.169—2
86181.2.32.170/31181.2.32.170 to 181.2.32.171—2
87181.2.32.172/31181.2.32.172 to 181.2.32.173—2
88181.2.32.174/31181.2.32.174 to 181.2.32.175—2
89181.2.32.176/31181.2.32.176 to 181.2.32.177—2
90181.2.32.178/31181.2.32.178 to 181.2.32.179—2
91181.2.32.180/31181.2.32.180 to 181.2.32.181—2
92181.2.32.182/31181.2.32.182 to 181.2.32.183—2
93181.2.32.184/31181.2.32.184 to 181.2.32.185—2
94181.2.32.186/31181.2.32.186 to 181.2.32.187—2
95181.2.32.188/31181.2.32.188 to 181.2.32.189—2
96181.2.32.190/31181.2.32.190 to 181.2.32.191—2
97181.2.32.192/31181.2.32.192 to 181.2.32.193—2
98181.2.32.194/31181.2.32.194 to 181.2.32.195—2
99181.2.32.196/31181.2.32.196 to 181.2.32.197—2
100181.2.32.198/31181.2.32.198 to 181.2.32.199—2
101181.2.32.200/31181.2.32.200 to 181.2.32.201—2
102181.2.32.202/31181.2.32.202 to 181.2.32.203—2
103181.2.32.204/31181.2.32.204 to 181.2.32.205—2
104181.2.32.206/31181.2.32.206 to 181.2.32.207—2
105181.2.32.208/31181.2.32.208 to 181.2.32.209—2
106181.2.32.210/31181.2.32.210 to 181.2.32.211—2
107181.2.32.212/31181.2.32.212 to 181.2.32.213—2
108181.2.32.214/31181.2.32.214 to 181.2.32.215—2
109181.2.32.216/31181.2.32.216 to 181.2.32.217—2
110181.2.32.218/31181.2.32.218 to 181.2.32.219—2
111181.2.32.220/31181.2.32.220 to 181.2.32.221—2
112181.2.32.222/31181.2.32.222 to 181.2.32.223—2
113181.2.32.224/31181.2.32.224 to 181.2.32.225—2
114181.2.32.226/31181.2.32.226 to 181.2.32.227—2
115181.2.32.228/31181.2.32.228 to 181.2.32.229—2
116181.2.32.230/31181.2.32.230 to 181.2.32.231—2
117181.2.32.232/31181.2.32.232 to 181.2.32.233—2
118181.2.32.234/31181.2.32.234 to 181.2.32.235—2
119181.2.32.236/31181.2.32.236 to 181.2.32.237—2
120181.2.32.238/31181.2.32.238 to 181.2.32.239—2
121181.2.32.240/31181.2.32.240 to 181.2.32.241—2
122181.2.32.242/31181.2.32.242 to 181.2.32.243—2
123181.2.32.244/31181.2.32.244 to 181.2.32.245—2
124181.2.32.246/31181.2.32.246 to 181.2.32.247—2
125181.2.32.248/31181.2.32.248 to 181.2.32.249—2
126181.2.32.250/31181.2.32.250 to 181.2.32.251—2
127181.2.32.252/31181.2.32.252 to 181.2.32.253—2
128181.2.32.254/31181.2.32.254 to 181.2.32.255—2
129181.2.33.0/31181.2.33.0 to 181.2.33.1—2
130181.2.33.2/31181.2.33.2 to 181.2.33.3—2
131181.2.33.4/31181.2.33.4 to 181.2.33.5—2
132181.2.33.6/31181.2.33.6 to 181.2.33.7—2
133181.2.33.8/31181.2.33.8 to 181.2.33.9—2
134181.2.33.10/31181.2.33.10 to 181.2.33.11—2
135181.2.33.12/31181.2.33.12 to 181.2.33.13—2
136181.2.33.14/31181.2.33.14 to 181.2.33.15—2
137181.2.33.16/31181.2.33.16 to 181.2.33.17—2
138181.2.33.18/31181.2.33.18 to 181.2.33.19—2
139181.2.33.20/31181.2.33.20 to 181.2.33.21—2
140181.2.33.22/31181.2.33.22 to 181.2.33.23—2
141181.2.33.24/31181.2.33.24 to 181.2.33.25—2
142181.2.33.26/31181.2.33.26 to 181.2.33.27—2
143181.2.33.28/31181.2.33.28 to 181.2.33.29—2
144181.2.33.30/31181.2.33.30 to 181.2.33.31—2
145181.2.33.32/31181.2.33.32 to 181.2.33.33—2
146181.2.33.34/31181.2.33.34 to 181.2.33.35—2
147181.2.33.36/31181.2.33.36 to 181.2.33.37—2
148181.2.33.38/31181.2.33.38 to 181.2.33.39—2
149181.2.33.40/31181.2.33.40 to 181.2.33.41—2
150181.2.33.42/31181.2.33.42 to 181.2.33.43—2
151181.2.33.44/31181.2.33.44 to 181.2.33.45—2
152181.2.33.46/31181.2.33.46 to 181.2.33.47—2
153181.2.33.48/31181.2.33.48 to 181.2.33.49—2
154181.2.33.50/31181.2.33.50 to 181.2.33.51—2
155181.2.33.52/31181.2.33.52 to 181.2.33.53—2
156181.2.33.54/31181.2.33.54 to 181.2.33.55—2
157181.2.33.56/31181.2.33.56 to 181.2.33.57—2
158181.2.33.58/31181.2.33.58 to 181.2.33.59—2
159181.2.33.60/31181.2.33.60 to 181.2.33.61—2
160181.2.33.62/31181.2.33.62 to 181.2.33.63—2
161181.2.33.64/31181.2.33.64 to 181.2.33.65—2
162181.2.33.66/31181.2.33.66 to 181.2.33.67—2
163181.2.33.68/31181.2.33.68 to 181.2.33.69—2
164181.2.33.70/31181.2.33.70 to 181.2.33.71—2
165181.2.33.72/31181.2.33.72 to 181.2.33.73—2
166181.2.33.74/31181.2.33.74 to 181.2.33.75—2
167181.2.33.76/31181.2.33.76 to 181.2.33.77—2
168181.2.33.78/31181.2.33.78 to 181.2.33.79—2
169181.2.33.80/31181.2.33.80 to 181.2.33.81—2
170181.2.33.82/31181.2.33.82 to 181.2.33.83—2
171181.2.33.84/31181.2.33.84 to 181.2.33.85—2
172181.2.33.86/31181.2.33.86 to 181.2.33.87—2
173181.2.33.88/31181.2.33.88 to 181.2.33.89—2
174181.2.33.90/31181.2.33.90 to 181.2.33.91—2
175181.2.33.92/31181.2.33.92 to 181.2.33.93—2
176181.2.33.94/31181.2.33.94 to 181.2.33.95—2
177181.2.33.96/31181.2.33.96 to 181.2.33.97—2
178181.2.33.98/31181.2.33.98 to 181.2.33.99—2
179181.2.33.100/31181.2.33.100 to 181.2.33.101—2
180181.2.33.102/31181.2.33.102 to 181.2.33.103—2
181181.2.33.104/31181.2.33.104 to 181.2.33.105—2
182181.2.33.106/31181.2.33.106 to 181.2.33.107—2
183181.2.33.108/31181.2.33.108 to 181.2.33.109—2
184181.2.33.110/31181.2.33.110 to 181.2.33.111—2
185181.2.33.112/31181.2.33.112 to 181.2.33.113—2
186181.2.33.114/31181.2.33.114 to 181.2.33.115—2
187181.2.33.116/31181.2.33.116 to 181.2.33.117—2
188181.2.33.118/31181.2.33.118 to 181.2.33.119—2
189181.2.33.120/31181.2.33.120 to 181.2.33.121—2
190181.2.33.122/31181.2.33.122 to 181.2.33.123—2
191181.2.33.124/31181.2.33.124 to 181.2.33.125—2
192181.2.33.126/31181.2.33.126 to 181.2.33.127—2
193181.2.33.128/31181.2.33.128 to 181.2.33.129—2
194181.2.33.130/31181.2.33.130 to 181.2.33.131—2
195181.2.33.132/31181.2.33.132 to 181.2.33.133—2
196181.2.33.134/31181.2.33.134 to 181.2.33.135—2
197181.2.33.136/31181.2.33.136 to 181.2.33.137—2
198181.2.33.138/31181.2.33.138 to 181.2.33.139—2
199181.2.33.140/31181.2.33.140 to 181.2.33.141—2
200181.2.33.142/31181.2.33.142 to 181.2.33.143—2
201181.2.33.144/31181.2.33.144 to 181.2.33.145—2
202181.2.33.146/31181.2.33.146 to 181.2.33.147—2
203181.2.33.148/31181.2.33.148 to 181.2.33.149—2
204181.2.33.150/31181.2.33.150 to 181.2.33.151—2
205181.2.33.152/31181.2.33.152 to 181.2.33.153—2
206181.2.33.154/31181.2.33.154 to 181.2.33.155—2
207181.2.33.156/31181.2.33.156 to 181.2.33.157—2
208181.2.33.158/31181.2.33.158 to 181.2.33.159—2
209181.2.33.160/31181.2.33.160 to 181.2.33.161—2
210181.2.33.162/31181.2.33.162 to 181.2.33.163—2
211181.2.33.164/31181.2.33.164 to 181.2.33.165—2
212181.2.33.166/31181.2.33.166 to 181.2.33.167—2
213181.2.33.168/31181.2.33.168 to 181.2.33.169—2
214181.2.33.170/31181.2.33.170 to 181.2.33.171—2
215181.2.33.172/31181.2.33.172 to 181.2.33.173—2
216181.2.33.174/31181.2.33.174 to 181.2.33.175—2
217181.2.33.176/31181.2.33.176 to 181.2.33.177—2
218181.2.33.178/31181.2.33.178 to 181.2.33.179—2
219181.2.33.180/31181.2.33.180 to 181.2.33.181—2
220181.2.33.182/31181.2.33.182 to 181.2.33.183—2
221181.2.33.184/31181.2.33.184 to 181.2.33.185—2
222181.2.33.186/31181.2.33.186 to 181.2.33.187—2
223181.2.33.188/31181.2.33.188 to 181.2.33.189—2
224181.2.33.190/31181.2.33.190 to 181.2.33.191—2
225181.2.33.192/31181.2.33.192 to 181.2.33.193—2
226181.2.33.194/31181.2.33.194 to 181.2.33.195—2
227181.2.33.196/31181.2.33.196 to 181.2.33.197—2
228181.2.33.198/31181.2.33.198 to 181.2.33.199—2
229181.2.33.200/31181.2.33.200 to 181.2.33.201—2
230181.2.33.202/31181.2.33.202 to 181.2.33.203—2
231181.2.33.204/31181.2.33.204 to 181.2.33.205—2
232181.2.33.206/31181.2.33.206 to 181.2.33.207—2
233181.2.33.208/31181.2.33.208 to 181.2.33.209—2
234181.2.33.210/31181.2.33.210 to 181.2.33.211—2
235181.2.33.212/31181.2.33.212 to 181.2.33.213—2
236181.2.33.214/31181.2.33.214 to 181.2.33.215—2
237181.2.33.216/31181.2.33.216 to 181.2.33.217—2
238181.2.33.218/31181.2.33.218 to 181.2.33.219—2
239181.2.33.220/31181.2.33.220 to 181.2.33.221—2
240181.2.33.222/31181.2.33.222 to 181.2.33.223—2
241181.2.33.224/31181.2.33.224 to 181.2.33.225—2
242181.2.33.226/31181.2.33.226 to 181.2.33.227—2
243181.2.33.228/31181.2.33.228 to 181.2.33.229—2
244181.2.33.230/31181.2.33.230 to 181.2.33.231—2
245181.2.33.232/31181.2.33.232 to 181.2.33.233—2
246181.2.33.234/31181.2.33.234 to 181.2.33.235—2
247181.2.33.236/31181.2.33.236 to 181.2.33.237—2
248181.2.33.238/31181.2.33.238 to 181.2.33.239—2
249181.2.33.240/31181.2.33.240 to 181.2.33.241—2
250181.2.33.242/31181.2.33.242 to 181.2.33.243—2
251181.2.33.244/31181.2.33.244 to 181.2.33.245—2
252181.2.33.246/31181.2.33.246 to 181.2.33.247—2
253181.2.33.248/31181.2.33.248 to 181.2.33.249—2
254181.2.33.250/31181.2.33.250 to 181.2.33.251—2
255181.2.33.252/31181.2.33.252 to 181.2.33.253—2
256181.2.33.254/31181.2.33.254 to 181.2.33.255—2

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.