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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.

Network237.6.232.0/21
Usable hosts2,046
Subnet mask255.255.248.0
Addresses2,048
Network address
237.6.232.0
Broadcast address
237.6.239.255
First usable
237.6.232.1
Last usable
237.6.239.254
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
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex ED06E800 · Integer 3976652800 to 3976654847
Reverse DNS zones
232.6.237.in-addr.arpa
233.6.237.in-addr.arpa
234.6.237.in-addr.arpa
235.6.237.in-addr.arpa
236.6.237.in-addr.arpa
237.6.237.in-addr.arpa
238.6.237.in-addr.arpa
239.6.237.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
Address11101101.00000110.11101000.00000000237.6.232.0
Subnet mask11111111.11111111.11111000.00000000255.255.248.0
Network11101101.00000110.11101000.00000000237.6.232.0
Broadcast11101101.00000110.11101111.11111111237.6.239.255
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)

237.6.232.0/21 makes 2,048 subnets of /32; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1237.6.232.0/32237.6.232.0 to 237.6.232.0—1
2237.6.232.1/32237.6.232.1 to 237.6.232.1—1
3237.6.232.2/32237.6.232.2 to 237.6.232.2—1
4237.6.232.3/32237.6.232.3 to 237.6.232.3—1
5237.6.232.4/32237.6.232.4 to 237.6.232.4—1
6237.6.232.5/32237.6.232.5 to 237.6.232.5—1
7237.6.232.6/32237.6.232.6 to 237.6.232.6—1
8237.6.232.7/32237.6.232.7 to 237.6.232.7—1
9237.6.232.8/32237.6.232.8 to 237.6.232.8—1
10237.6.232.9/32237.6.232.9 to 237.6.232.9—1
11237.6.232.10/32237.6.232.10 to 237.6.232.10—1
12237.6.232.11/32237.6.232.11 to 237.6.232.11—1
13237.6.232.12/32237.6.232.12 to 237.6.232.12—1
14237.6.232.13/32237.6.232.13 to 237.6.232.13—1
15237.6.232.14/32237.6.232.14 to 237.6.232.14—1
16237.6.232.15/32237.6.232.15 to 237.6.232.15—1
17237.6.232.16/32237.6.232.16 to 237.6.232.16—1
18237.6.232.17/32237.6.232.17 to 237.6.232.17—1
19237.6.232.18/32237.6.232.18 to 237.6.232.18—1
20237.6.232.19/32237.6.232.19 to 237.6.232.19—1
21237.6.232.20/32237.6.232.20 to 237.6.232.20—1
22237.6.232.21/32237.6.232.21 to 237.6.232.21—1
23237.6.232.22/32237.6.232.22 to 237.6.232.22—1
24237.6.232.23/32237.6.232.23 to 237.6.232.23—1
25237.6.232.24/32237.6.232.24 to 237.6.232.24—1
26237.6.232.25/32237.6.232.25 to 237.6.232.25—1
27237.6.232.26/32237.6.232.26 to 237.6.232.26—1
28237.6.232.27/32237.6.232.27 to 237.6.232.27—1
29237.6.232.28/32237.6.232.28 to 237.6.232.28—1
30237.6.232.29/32237.6.232.29 to 237.6.232.29—1
31237.6.232.30/32237.6.232.30 to 237.6.232.30—1
32237.6.232.31/32237.6.232.31 to 237.6.232.31—1
33237.6.232.32/32237.6.232.32 to 237.6.232.32—1
34237.6.232.33/32237.6.232.33 to 237.6.232.33—1
35237.6.232.34/32237.6.232.34 to 237.6.232.34—1
36237.6.232.35/32237.6.232.35 to 237.6.232.35—1
37237.6.232.36/32237.6.232.36 to 237.6.232.36—1
38237.6.232.37/32237.6.232.37 to 237.6.232.37—1
39237.6.232.38/32237.6.232.38 to 237.6.232.38—1
40237.6.232.39/32237.6.232.39 to 237.6.232.39—1
41237.6.232.40/32237.6.232.40 to 237.6.232.40—1
42237.6.232.41/32237.6.232.41 to 237.6.232.41—1
43237.6.232.42/32237.6.232.42 to 237.6.232.42—1
44237.6.232.43/32237.6.232.43 to 237.6.232.43—1
45237.6.232.44/32237.6.232.44 to 237.6.232.44—1
46237.6.232.45/32237.6.232.45 to 237.6.232.45—1
47237.6.232.46/32237.6.232.46 to 237.6.232.46—1
48237.6.232.47/32237.6.232.47 to 237.6.232.47—1
49237.6.232.48/32237.6.232.48 to 237.6.232.48—1
50237.6.232.49/32237.6.232.49 to 237.6.232.49—1
51237.6.232.50/32237.6.232.50 to 237.6.232.50—1
52237.6.232.51/32237.6.232.51 to 237.6.232.51—1
53237.6.232.52/32237.6.232.52 to 237.6.232.52—1
54237.6.232.53/32237.6.232.53 to 237.6.232.53—1
55237.6.232.54/32237.6.232.54 to 237.6.232.54—1
56237.6.232.55/32237.6.232.55 to 237.6.232.55—1
57237.6.232.56/32237.6.232.56 to 237.6.232.56—1
58237.6.232.57/32237.6.232.57 to 237.6.232.57—1
59237.6.232.58/32237.6.232.58 to 237.6.232.58—1
60237.6.232.59/32237.6.232.59 to 237.6.232.59—1
61237.6.232.60/32237.6.232.60 to 237.6.232.60—1
62237.6.232.61/32237.6.232.61 to 237.6.232.61—1
63237.6.232.62/32237.6.232.62 to 237.6.232.62—1
64237.6.232.63/32237.6.232.63 to 237.6.232.63—1
65237.6.232.64/32237.6.232.64 to 237.6.232.64—1
66237.6.232.65/32237.6.232.65 to 237.6.232.65—1
67237.6.232.66/32237.6.232.66 to 237.6.232.66—1
68237.6.232.67/32237.6.232.67 to 237.6.232.67—1
69237.6.232.68/32237.6.232.68 to 237.6.232.68—1
70237.6.232.69/32237.6.232.69 to 237.6.232.69—1
71237.6.232.70/32237.6.232.70 to 237.6.232.70—1
72237.6.232.71/32237.6.232.71 to 237.6.232.71—1
73237.6.232.72/32237.6.232.72 to 237.6.232.72—1
74237.6.232.73/32237.6.232.73 to 237.6.232.73—1
75237.6.232.74/32237.6.232.74 to 237.6.232.74—1
76237.6.232.75/32237.6.232.75 to 237.6.232.75—1
77237.6.232.76/32237.6.232.76 to 237.6.232.76—1
78237.6.232.77/32237.6.232.77 to 237.6.232.77—1
79237.6.232.78/32237.6.232.78 to 237.6.232.78—1
80237.6.232.79/32237.6.232.79 to 237.6.232.79—1
81237.6.232.80/32237.6.232.80 to 237.6.232.80—1
82237.6.232.81/32237.6.232.81 to 237.6.232.81—1
83237.6.232.82/32237.6.232.82 to 237.6.232.82—1
84237.6.232.83/32237.6.232.83 to 237.6.232.83—1
85237.6.232.84/32237.6.232.84 to 237.6.232.84—1
86237.6.232.85/32237.6.232.85 to 237.6.232.85—1
87237.6.232.86/32237.6.232.86 to 237.6.232.86—1
88237.6.232.87/32237.6.232.87 to 237.6.232.87—1
89237.6.232.88/32237.6.232.88 to 237.6.232.88—1
90237.6.232.89/32237.6.232.89 to 237.6.232.89—1
91237.6.232.90/32237.6.232.90 to 237.6.232.90—1
92237.6.232.91/32237.6.232.91 to 237.6.232.91—1
93237.6.232.92/32237.6.232.92 to 237.6.232.92—1
94237.6.232.93/32237.6.232.93 to 237.6.232.93—1
95237.6.232.94/32237.6.232.94 to 237.6.232.94—1
96237.6.232.95/32237.6.232.95 to 237.6.232.95—1
97237.6.232.96/32237.6.232.96 to 237.6.232.96—1
98237.6.232.97/32237.6.232.97 to 237.6.232.97—1
99237.6.232.98/32237.6.232.98 to 237.6.232.98—1
100237.6.232.99/32237.6.232.99 to 237.6.232.99—1
101237.6.232.100/32237.6.232.100 to 237.6.232.100—1
102237.6.232.101/32237.6.232.101 to 237.6.232.101—1
103237.6.232.102/32237.6.232.102 to 237.6.232.102—1
104237.6.232.103/32237.6.232.103 to 237.6.232.103—1
105237.6.232.104/32237.6.232.104 to 237.6.232.104—1
106237.6.232.105/32237.6.232.105 to 237.6.232.105—1
107237.6.232.106/32237.6.232.106 to 237.6.232.106—1
108237.6.232.107/32237.6.232.107 to 237.6.232.107—1
109237.6.232.108/32237.6.232.108 to 237.6.232.108—1
110237.6.232.109/32237.6.232.109 to 237.6.232.109—1
111237.6.232.110/32237.6.232.110 to 237.6.232.110—1
112237.6.232.111/32237.6.232.111 to 237.6.232.111—1
113237.6.232.112/32237.6.232.112 to 237.6.232.112—1
114237.6.232.113/32237.6.232.113 to 237.6.232.113—1
115237.6.232.114/32237.6.232.114 to 237.6.232.114—1
116237.6.232.115/32237.6.232.115 to 237.6.232.115—1
117237.6.232.116/32237.6.232.116 to 237.6.232.116—1
118237.6.232.117/32237.6.232.117 to 237.6.232.117—1
119237.6.232.118/32237.6.232.118 to 237.6.232.118—1
120237.6.232.119/32237.6.232.119 to 237.6.232.119—1
121237.6.232.120/32237.6.232.120 to 237.6.232.120—1
122237.6.232.121/32237.6.232.121 to 237.6.232.121—1
123237.6.232.122/32237.6.232.122 to 237.6.232.122—1
124237.6.232.123/32237.6.232.123 to 237.6.232.123—1
125237.6.232.124/32237.6.232.124 to 237.6.232.124—1
126237.6.232.125/32237.6.232.125 to 237.6.232.125—1
127237.6.232.126/32237.6.232.126 to 237.6.232.126—1
128237.6.232.127/32237.6.232.127 to 237.6.232.127—1
129237.6.232.128/32237.6.232.128 to 237.6.232.128—1
130237.6.232.129/32237.6.232.129 to 237.6.232.129—1
131237.6.232.130/32237.6.232.130 to 237.6.232.130—1
132237.6.232.131/32237.6.232.131 to 237.6.232.131—1
133237.6.232.132/32237.6.232.132 to 237.6.232.132—1
134237.6.232.133/32237.6.232.133 to 237.6.232.133—1
135237.6.232.134/32237.6.232.134 to 237.6.232.134—1
136237.6.232.135/32237.6.232.135 to 237.6.232.135—1
137237.6.232.136/32237.6.232.136 to 237.6.232.136—1
138237.6.232.137/32237.6.232.137 to 237.6.232.137—1
139237.6.232.138/32237.6.232.138 to 237.6.232.138—1
140237.6.232.139/32237.6.232.139 to 237.6.232.139—1
141237.6.232.140/32237.6.232.140 to 237.6.232.140—1
142237.6.232.141/32237.6.232.141 to 237.6.232.141—1
143237.6.232.142/32237.6.232.142 to 237.6.232.142—1
144237.6.232.143/32237.6.232.143 to 237.6.232.143—1
145237.6.232.144/32237.6.232.144 to 237.6.232.144—1
146237.6.232.145/32237.6.232.145 to 237.6.232.145—1
147237.6.232.146/32237.6.232.146 to 237.6.232.146—1
148237.6.232.147/32237.6.232.147 to 237.6.232.147—1
149237.6.232.148/32237.6.232.148 to 237.6.232.148—1
150237.6.232.149/32237.6.232.149 to 237.6.232.149—1
151237.6.232.150/32237.6.232.150 to 237.6.232.150—1
152237.6.232.151/32237.6.232.151 to 237.6.232.151—1
153237.6.232.152/32237.6.232.152 to 237.6.232.152—1
154237.6.232.153/32237.6.232.153 to 237.6.232.153—1
155237.6.232.154/32237.6.232.154 to 237.6.232.154—1
156237.6.232.155/32237.6.232.155 to 237.6.232.155—1
157237.6.232.156/32237.6.232.156 to 237.6.232.156—1
158237.6.232.157/32237.6.232.157 to 237.6.232.157—1
159237.6.232.158/32237.6.232.158 to 237.6.232.158—1
160237.6.232.159/32237.6.232.159 to 237.6.232.159—1
161237.6.232.160/32237.6.232.160 to 237.6.232.160—1
162237.6.232.161/32237.6.232.161 to 237.6.232.161—1
163237.6.232.162/32237.6.232.162 to 237.6.232.162—1
164237.6.232.163/32237.6.232.163 to 237.6.232.163—1
165237.6.232.164/32237.6.232.164 to 237.6.232.164—1
166237.6.232.165/32237.6.232.165 to 237.6.232.165—1
167237.6.232.166/32237.6.232.166 to 237.6.232.166—1
168237.6.232.167/32237.6.232.167 to 237.6.232.167—1
169237.6.232.168/32237.6.232.168 to 237.6.232.168—1
170237.6.232.169/32237.6.232.169 to 237.6.232.169—1
171237.6.232.170/32237.6.232.170 to 237.6.232.170—1
172237.6.232.171/32237.6.232.171 to 237.6.232.171—1
173237.6.232.172/32237.6.232.172 to 237.6.232.172—1
174237.6.232.173/32237.6.232.173 to 237.6.232.173—1
175237.6.232.174/32237.6.232.174 to 237.6.232.174—1
176237.6.232.175/32237.6.232.175 to 237.6.232.175—1
177237.6.232.176/32237.6.232.176 to 237.6.232.176—1
178237.6.232.177/32237.6.232.177 to 237.6.232.177—1
179237.6.232.178/32237.6.232.178 to 237.6.232.178—1
180237.6.232.179/32237.6.232.179 to 237.6.232.179—1
181237.6.232.180/32237.6.232.180 to 237.6.232.180—1
182237.6.232.181/32237.6.232.181 to 237.6.232.181—1
183237.6.232.182/32237.6.232.182 to 237.6.232.182—1
184237.6.232.183/32237.6.232.183 to 237.6.232.183—1
185237.6.232.184/32237.6.232.184 to 237.6.232.184—1
186237.6.232.185/32237.6.232.185 to 237.6.232.185—1
187237.6.232.186/32237.6.232.186 to 237.6.232.186—1
188237.6.232.187/32237.6.232.187 to 237.6.232.187—1
189237.6.232.188/32237.6.232.188 to 237.6.232.188—1
190237.6.232.189/32237.6.232.189 to 237.6.232.189—1
191237.6.232.190/32237.6.232.190 to 237.6.232.190—1
192237.6.232.191/32237.6.232.191 to 237.6.232.191—1
193237.6.232.192/32237.6.232.192 to 237.6.232.192—1
194237.6.232.193/32237.6.232.193 to 237.6.232.193—1
195237.6.232.194/32237.6.232.194 to 237.6.232.194—1
196237.6.232.195/32237.6.232.195 to 237.6.232.195—1
197237.6.232.196/32237.6.232.196 to 237.6.232.196—1
198237.6.232.197/32237.6.232.197 to 237.6.232.197—1
199237.6.232.198/32237.6.232.198 to 237.6.232.198—1
200237.6.232.199/32237.6.232.199 to 237.6.232.199—1
201237.6.232.200/32237.6.232.200 to 237.6.232.200—1
202237.6.232.201/32237.6.232.201 to 237.6.232.201—1
203237.6.232.202/32237.6.232.202 to 237.6.232.202—1
204237.6.232.203/32237.6.232.203 to 237.6.232.203—1
205237.6.232.204/32237.6.232.204 to 237.6.232.204—1
206237.6.232.205/32237.6.232.205 to 237.6.232.205—1
207237.6.232.206/32237.6.232.206 to 237.6.232.206—1
208237.6.232.207/32237.6.232.207 to 237.6.232.207—1
209237.6.232.208/32237.6.232.208 to 237.6.232.208—1
210237.6.232.209/32237.6.232.209 to 237.6.232.209—1
211237.6.232.210/32237.6.232.210 to 237.6.232.210—1
212237.6.232.211/32237.6.232.211 to 237.6.232.211—1
213237.6.232.212/32237.6.232.212 to 237.6.232.212—1
214237.6.232.213/32237.6.232.213 to 237.6.232.213—1
215237.6.232.214/32237.6.232.214 to 237.6.232.214—1
216237.6.232.215/32237.6.232.215 to 237.6.232.215—1
217237.6.232.216/32237.6.232.216 to 237.6.232.216—1
218237.6.232.217/32237.6.232.217 to 237.6.232.217—1
219237.6.232.218/32237.6.232.218 to 237.6.232.218—1
220237.6.232.219/32237.6.232.219 to 237.6.232.219—1
221237.6.232.220/32237.6.232.220 to 237.6.232.220—1
222237.6.232.221/32237.6.232.221 to 237.6.232.221—1
223237.6.232.222/32237.6.232.222 to 237.6.232.222—1
224237.6.232.223/32237.6.232.223 to 237.6.232.223—1
225237.6.232.224/32237.6.232.224 to 237.6.232.224—1
226237.6.232.225/32237.6.232.225 to 237.6.232.225—1
227237.6.232.226/32237.6.232.226 to 237.6.232.226—1
228237.6.232.227/32237.6.232.227 to 237.6.232.227—1
229237.6.232.228/32237.6.232.228 to 237.6.232.228—1
230237.6.232.229/32237.6.232.229 to 237.6.232.229—1
231237.6.232.230/32237.6.232.230 to 237.6.232.230—1
232237.6.232.231/32237.6.232.231 to 237.6.232.231—1
233237.6.232.232/32237.6.232.232 to 237.6.232.232—1
234237.6.232.233/32237.6.232.233 to 237.6.232.233—1
235237.6.232.234/32237.6.232.234 to 237.6.232.234—1
236237.6.232.235/32237.6.232.235 to 237.6.232.235—1
237237.6.232.236/32237.6.232.236 to 237.6.232.236—1
238237.6.232.237/32237.6.232.237 to 237.6.232.237—1
239237.6.232.238/32237.6.232.238 to 237.6.232.238—1
240237.6.232.239/32237.6.232.239 to 237.6.232.239—1
241237.6.232.240/32237.6.232.240 to 237.6.232.240—1
242237.6.232.241/32237.6.232.241 to 237.6.232.241—1
243237.6.232.242/32237.6.232.242 to 237.6.232.242—1
244237.6.232.243/32237.6.232.243 to 237.6.232.243—1
245237.6.232.244/32237.6.232.244 to 237.6.232.244—1
246237.6.232.245/32237.6.232.245 to 237.6.232.245—1
247237.6.232.246/32237.6.232.246 to 237.6.232.246—1
248237.6.232.247/32237.6.232.247 to 237.6.232.247—1
249237.6.232.248/32237.6.232.248 to 237.6.232.248—1
250237.6.232.249/32237.6.232.249 to 237.6.232.249—1
251237.6.232.250/32237.6.232.250 to 237.6.232.250—1
252237.6.232.251/32237.6.232.251 to 237.6.232.251—1
253237.6.232.252/32237.6.232.252 to 237.6.232.252—1
254237.6.232.253/32237.6.232.253 to 237.6.232.253—1
255237.6.232.254/32237.6.232.254 to 237.6.232.254—1
256237.6.232.255/32237.6.232.255 to 237.6.232.255—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.