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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.

Network205.3.16.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
205.3.16.0
Broadcast address
205.3.31.255
First usable
205.3.16.1
Last usable
205.3.31.254
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
C (default /24)
As numbers
Hex CD031000 · Integer 3439529984 to 3439534079
Reverse DNS zones
16.3.205.in-addr.arpa
17.3.205.in-addr.arpa
18.3.205.in-addr.arpa
19.3.205.in-addr.arpa
20.3.205.in-addr.arpa
21.3.205.in-addr.arpa
22.3.205.in-addr.arpa
23.3.205.in-addr.arpa
24.3.205.in-addr.arpa
25.3.205.in-addr.arpa
26.3.205.in-addr.arpa
27.3.205.in-addr.arpa
28.3.205.in-addr.arpa
29.3.205.in-addr.arpa
30.3.205.in-addr.arpa
31.3.205.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
Address11001101.00000011.00010000.00000000205.3.16.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network11001101.00000011.00010000.00000000205.3.16.0
Broadcast11001101.00000011.00011111.11111111205.3.31.255
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)

205.3.16.0/20 makes 4,096 subnets of /32; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1205.3.16.0/32205.3.16.0 to 205.3.16.0—1
2205.3.16.1/32205.3.16.1 to 205.3.16.1—1
3205.3.16.2/32205.3.16.2 to 205.3.16.2—1
4205.3.16.3/32205.3.16.3 to 205.3.16.3—1
5205.3.16.4/32205.3.16.4 to 205.3.16.4—1
6205.3.16.5/32205.3.16.5 to 205.3.16.5—1
7205.3.16.6/32205.3.16.6 to 205.3.16.6—1
8205.3.16.7/32205.3.16.7 to 205.3.16.7—1
9205.3.16.8/32205.3.16.8 to 205.3.16.8—1
10205.3.16.9/32205.3.16.9 to 205.3.16.9—1
11205.3.16.10/32205.3.16.10 to 205.3.16.10—1
12205.3.16.11/32205.3.16.11 to 205.3.16.11—1
13205.3.16.12/32205.3.16.12 to 205.3.16.12—1
14205.3.16.13/32205.3.16.13 to 205.3.16.13—1
15205.3.16.14/32205.3.16.14 to 205.3.16.14—1
16205.3.16.15/32205.3.16.15 to 205.3.16.15—1
17205.3.16.16/32205.3.16.16 to 205.3.16.16—1
18205.3.16.17/32205.3.16.17 to 205.3.16.17—1
19205.3.16.18/32205.3.16.18 to 205.3.16.18—1
20205.3.16.19/32205.3.16.19 to 205.3.16.19—1
21205.3.16.20/32205.3.16.20 to 205.3.16.20—1
22205.3.16.21/32205.3.16.21 to 205.3.16.21—1
23205.3.16.22/32205.3.16.22 to 205.3.16.22—1
24205.3.16.23/32205.3.16.23 to 205.3.16.23—1
25205.3.16.24/32205.3.16.24 to 205.3.16.24—1
26205.3.16.25/32205.3.16.25 to 205.3.16.25—1
27205.3.16.26/32205.3.16.26 to 205.3.16.26—1
28205.3.16.27/32205.3.16.27 to 205.3.16.27—1
29205.3.16.28/32205.3.16.28 to 205.3.16.28—1
30205.3.16.29/32205.3.16.29 to 205.3.16.29—1
31205.3.16.30/32205.3.16.30 to 205.3.16.30—1
32205.3.16.31/32205.3.16.31 to 205.3.16.31—1
33205.3.16.32/32205.3.16.32 to 205.3.16.32—1
34205.3.16.33/32205.3.16.33 to 205.3.16.33—1
35205.3.16.34/32205.3.16.34 to 205.3.16.34—1
36205.3.16.35/32205.3.16.35 to 205.3.16.35—1
37205.3.16.36/32205.3.16.36 to 205.3.16.36—1
38205.3.16.37/32205.3.16.37 to 205.3.16.37—1
39205.3.16.38/32205.3.16.38 to 205.3.16.38—1
40205.3.16.39/32205.3.16.39 to 205.3.16.39—1
41205.3.16.40/32205.3.16.40 to 205.3.16.40—1
42205.3.16.41/32205.3.16.41 to 205.3.16.41—1
43205.3.16.42/32205.3.16.42 to 205.3.16.42—1
44205.3.16.43/32205.3.16.43 to 205.3.16.43—1
45205.3.16.44/32205.3.16.44 to 205.3.16.44—1
46205.3.16.45/32205.3.16.45 to 205.3.16.45—1
47205.3.16.46/32205.3.16.46 to 205.3.16.46—1
48205.3.16.47/32205.3.16.47 to 205.3.16.47—1
49205.3.16.48/32205.3.16.48 to 205.3.16.48—1
50205.3.16.49/32205.3.16.49 to 205.3.16.49—1
51205.3.16.50/32205.3.16.50 to 205.3.16.50—1
52205.3.16.51/32205.3.16.51 to 205.3.16.51—1
53205.3.16.52/32205.3.16.52 to 205.3.16.52—1
54205.3.16.53/32205.3.16.53 to 205.3.16.53—1
55205.3.16.54/32205.3.16.54 to 205.3.16.54—1
56205.3.16.55/32205.3.16.55 to 205.3.16.55—1
57205.3.16.56/32205.3.16.56 to 205.3.16.56—1
58205.3.16.57/32205.3.16.57 to 205.3.16.57—1
59205.3.16.58/32205.3.16.58 to 205.3.16.58—1
60205.3.16.59/32205.3.16.59 to 205.3.16.59—1
61205.3.16.60/32205.3.16.60 to 205.3.16.60—1
62205.3.16.61/32205.3.16.61 to 205.3.16.61—1
63205.3.16.62/32205.3.16.62 to 205.3.16.62—1
64205.3.16.63/32205.3.16.63 to 205.3.16.63—1
65205.3.16.64/32205.3.16.64 to 205.3.16.64—1
66205.3.16.65/32205.3.16.65 to 205.3.16.65—1
67205.3.16.66/32205.3.16.66 to 205.3.16.66—1
68205.3.16.67/32205.3.16.67 to 205.3.16.67—1
69205.3.16.68/32205.3.16.68 to 205.3.16.68—1
70205.3.16.69/32205.3.16.69 to 205.3.16.69—1
71205.3.16.70/32205.3.16.70 to 205.3.16.70—1
72205.3.16.71/32205.3.16.71 to 205.3.16.71—1
73205.3.16.72/32205.3.16.72 to 205.3.16.72—1
74205.3.16.73/32205.3.16.73 to 205.3.16.73—1
75205.3.16.74/32205.3.16.74 to 205.3.16.74—1
76205.3.16.75/32205.3.16.75 to 205.3.16.75—1
77205.3.16.76/32205.3.16.76 to 205.3.16.76—1
78205.3.16.77/32205.3.16.77 to 205.3.16.77—1
79205.3.16.78/32205.3.16.78 to 205.3.16.78—1
80205.3.16.79/32205.3.16.79 to 205.3.16.79—1
81205.3.16.80/32205.3.16.80 to 205.3.16.80—1
82205.3.16.81/32205.3.16.81 to 205.3.16.81—1
83205.3.16.82/32205.3.16.82 to 205.3.16.82—1
84205.3.16.83/32205.3.16.83 to 205.3.16.83—1
85205.3.16.84/32205.3.16.84 to 205.3.16.84—1
86205.3.16.85/32205.3.16.85 to 205.3.16.85—1
87205.3.16.86/32205.3.16.86 to 205.3.16.86—1
88205.3.16.87/32205.3.16.87 to 205.3.16.87—1
89205.3.16.88/32205.3.16.88 to 205.3.16.88—1
90205.3.16.89/32205.3.16.89 to 205.3.16.89—1
91205.3.16.90/32205.3.16.90 to 205.3.16.90—1
92205.3.16.91/32205.3.16.91 to 205.3.16.91—1
93205.3.16.92/32205.3.16.92 to 205.3.16.92—1
94205.3.16.93/32205.3.16.93 to 205.3.16.93—1
95205.3.16.94/32205.3.16.94 to 205.3.16.94—1
96205.3.16.95/32205.3.16.95 to 205.3.16.95—1
97205.3.16.96/32205.3.16.96 to 205.3.16.96—1
98205.3.16.97/32205.3.16.97 to 205.3.16.97—1
99205.3.16.98/32205.3.16.98 to 205.3.16.98—1
100205.3.16.99/32205.3.16.99 to 205.3.16.99—1
101205.3.16.100/32205.3.16.100 to 205.3.16.100—1
102205.3.16.101/32205.3.16.101 to 205.3.16.101—1
103205.3.16.102/32205.3.16.102 to 205.3.16.102—1
104205.3.16.103/32205.3.16.103 to 205.3.16.103—1
105205.3.16.104/32205.3.16.104 to 205.3.16.104—1
106205.3.16.105/32205.3.16.105 to 205.3.16.105—1
107205.3.16.106/32205.3.16.106 to 205.3.16.106—1
108205.3.16.107/32205.3.16.107 to 205.3.16.107—1
109205.3.16.108/32205.3.16.108 to 205.3.16.108—1
110205.3.16.109/32205.3.16.109 to 205.3.16.109—1
111205.3.16.110/32205.3.16.110 to 205.3.16.110—1
112205.3.16.111/32205.3.16.111 to 205.3.16.111—1
113205.3.16.112/32205.3.16.112 to 205.3.16.112—1
114205.3.16.113/32205.3.16.113 to 205.3.16.113—1
115205.3.16.114/32205.3.16.114 to 205.3.16.114—1
116205.3.16.115/32205.3.16.115 to 205.3.16.115—1
117205.3.16.116/32205.3.16.116 to 205.3.16.116—1
118205.3.16.117/32205.3.16.117 to 205.3.16.117—1
119205.3.16.118/32205.3.16.118 to 205.3.16.118—1
120205.3.16.119/32205.3.16.119 to 205.3.16.119—1
121205.3.16.120/32205.3.16.120 to 205.3.16.120—1
122205.3.16.121/32205.3.16.121 to 205.3.16.121—1
123205.3.16.122/32205.3.16.122 to 205.3.16.122—1
124205.3.16.123/32205.3.16.123 to 205.3.16.123—1
125205.3.16.124/32205.3.16.124 to 205.3.16.124—1
126205.3.16.125/32205.3.16.125 to 205.3.16.125—1
127205.3.16.126/32205.3.16.126 to 205.3.16.126—1
128205.3.16.127/32205.3.16.127 to 205.3.16.127—1
129205.3.16.128/32205.3.16.128 to 205.3.16.128—1
130205.3.16.129/32205.3.16.129 to 205.3.16.129—1
131205.3.16.130/32205.3.16.130 to 205.3.16.130—1
132205.3.16.131/32205.3.16.131 to 205.3.16.131—1
133205.3.16.132/32205.3.16.132 to 205.3.16.132—1
134205.3.16.133/32205.3.16.133 to 205.3.16.133—1
135205.3.16.134/32205.3.16.134 to 205.3.16.134—1
136205.3.16.135/32205.3.16.135 to 205.3.16.135—1
137205.3.16.136/32205.3.16.136 to 205.3.16.136—1
138205.3.16.137/32205.3.16.137 to 205.3.16.137—1
139205.3.16.138/32205.3.16.138 to 205.3.16.138—1
140205.3.16.139/32205.3.16.139 to 205.3.16.139—1
141205.3.16.140/32205.3.16.140 to 205.3.16.140—1
142205.3.16.141/32205.3.16.141 to 205.3.16.141—1
143205.3.16.142/32205.3.16.142 to 205.3.16.142—1
144205.3.16.143/32205.3.16.143 to 205.3.16.143—1
145205.3.16.144/32205.3.16.144 to 205.3.16.144—1
146205.3.16.145/32205.3.16.145 to 205.3.16.145—1
147205.3.16.146/32205.3.16.146 to 205.3.16.146—1
148205.3.16.147/32205.3.16.147 to 205.3.16.147—1
149205.3.16.148/32205.3.16.148 to 205.3.16.148—1
150205.3.16.149/32205.3.16.149 to 205.3.16.149—1
151205.3.16.150/32205.3.16.150 to 205.3.16.150—1
152205.3.16.151/32205.3.16.151 to 205.3.16.151—1
153205.3.16.152/32205.3.16.152 to 205.3.16.152—1
154205.3.16.153/32205.3.16.153 to 205.3.16.153—1
155205.3.16.154/32205.3.16.154 to 205.3.16.154—1
156205.3.16.155/32205.3.16.155 to 205.3.16.155—1
157205.3.16.156/32205.3.16.156 to 205.3.16.156—1
158205.3.16.157/32205.3.16.157 to 205.3.16.157—1
159205.3.16.158/32205.3.16.158 to 205.3.16.158—1
160205.3.16.159/32205.3.16.159 to 205.3.16.159—1
161205.3.16.160/32205.3.16.160 to 205.3.16.160—1
162205.3.16.161/32205.3.16.161 to 205.3.16.161—1
163205.3.16.162/32205.3.16.162 to 205.3.16.162—1
164205.3.16.163/32205.3.16.163 to 205.3.16.163—1
165205.3.16.164/32205.3.16.164 to 205.3.16.164—1
166205.3.16.165/32205.3.16.165 to 205.3.16.165—1
167205.3.16.166/32205.3.16.166 to 205.3.16.166—1
168205.3.16.167/32205.3.16.167 to 205.3.16.167—1
169205.3.16.168/32205.3.16.168 to 205.3.16.168—1
170205.3.16.169/32205.3.16.169 to 205.3.16.169—1
171205.3.16.170/32205.3.16.170 to 205.3.16.170—1
172205.3.16.171/32205.3.16.171 to 205.3.16.171—1
173205.3.16.172/32205.3.16.172 to 205.3.16.172—1
174205.3.16.173/32205.3.16.173 to 205.3.16.173—1
175205.3.16.174/32205.3.16.174 to 205.3.16.174—1
176205.3.16.175/32205.3.16.175 to 205.3.16.175—1
177205.3.16.176/32205.3.16.176 to 205.3.16.176—1
178205.3.16.177/32205.3.16.177 to 205.3.16.177—1
179205.3.16.178/32205.3.16.178 to 205.3.16.178—1
180205.3.16.179/32205.3.16.179 to 205.3.16.179—1
181205.3.16.180/32205.3.16.180 to 205.3.16.180—1
182205.3.16.181/32205.3.16.181 to 205.3.16.181—1
183205.3.16.182/32205.3.16.182 to 205.3.16.182—1
184205.3.16.183/32205.3.16.183 to 205.3.16.183—1
185205.3.16.184/32205.3.16.184 to 205.3.16.184—1
186205.3.16.185/32205.3.16.185 to 205.3.16.185—1
187205.3.16.186/32205.3.16.186 to 205.3.16.186—1
188205.3.16.187/32205.3.16.187 to 205.3.16.187—1
189205.3.16.188/32205.3.16.188 to 205.3.16.188—1
190205.3.16.189/32205.3.16.189 to 205.3.16.189—1
191205.3.16.190/32205.3.16.190 to 205.3.16.190—1
192205.3.16.191/32205.3.16.191 to 205.3.16.191—1
193205.3.16.192/32205.3.16.192 to 205.3.16.192—1
194205.3.16.193/32205.3.16.193 to 205.3.16.193—1
195205.3.16.194/32205.3.16.194 to 205.3.16.194—1
196205.3.16.195/32205.3.16.195 to 205.3.16.195—1
197205.3.16.196/32205.3.16.196 to 205.3.16.196—1
198205.3.16.197/32205.3.16.197 to 205.3.16.197—1
199205.3.16.198/32205.3.16.198 to 205.3.16.198—1
200205.3.16.199/32205.3.16.199 to 205.3.16.199—1
201205.3.16.200/32205.3.16.200 to 205.3.16.200—1
202205.3.16.201/32205.3.16.201 to 205.3.16.201—1
203205.3.16.202/32205.3.16.202 to 205.3.16.202—1
204205.3.16.203/32205.3.16.203 to 205.3.16.203—1
205205.3.16.204/32205.3.16.204 to 205.3.16.204—1
206205.3.16.205/32205.3.16.205 to 205.3.16.205—1
207205.3.16.206/32205.3.16.206 to 205.3.16.206—1
208205.3.16.207/32205.3.16.207 to 205.3.16.207—1
209205.3.16.208/32205.3.16.208 to 205.3.16.208—1
210205.3.16.209/32205.3.16.209 to 205.3.16.209—1
211205.3.16.210/32205.3.16.210 to 205.3.16.210—1
212205.3.16.211/32205.3.16.211 to 205.3.16.211—1
213205.3.16.212/32205.3.16.212 to 205.3.16.212—1
214205.3.16.213/32205.3.16.213 to 205.3.16.213—1
215205.3.16.214/32205.3.16.214 to 205.3.16.214—1
216205.3.16.215/32205.3.16.215 to 205.3.16.215—1
217205.3.16.216/32205.3.16.216 to 205.3.16.216—1
218205.3.16.217/32205.3.16.217 to 205.3.16.217—1
219205.3.16.218/32205.3.16.218 to 205.3.16.218—1
220205.3.16.219/32205.3.16.219 to 205.3.16.219—1
221205.3.16.220/32205.3.16.220 to 205.3.16.220—1
222205.3.16.221/32205.3.16.221 to 205.3.16.221—1
223205.3.16.222/32205.3.16.222 to 205.3.16.222—1
224205.3.16.223/32205.3.16.223 to 205.3.16.223—1
225205.3.16.224/32205.3.16.224 to 205.3.16.224—1
226205.3.16.225/32205.3.16.225 to 205.3.16.225—1
227205.3.16.226/32205.3.16.226 to 205.3.16.226—1
228205.3.16.227/32205.3.16.227 to 205.3.16.227—1
229205.3.16.228/32205.3.16.228 to 205.3.16.228—1
230205.3.16.229/32205.3.16.229 to 205.3.16.229—1
231205.3.16.230/32205.3.16.230 to 205.3.16.230—1
232205.3.16.231/32205.3.16.231 to 205.3.16.231—1
233205.3.16.232/32205.3.16.232 to 205.3.16.232—1
234205.3.16.233/32205.3.16.233 to 205.3.16.233—1
235205.3.16.234/32205.3.16.234 to 205.3.16.234—1
236205.3.16.235/32205.3.16.235 to 205.3.16.235—1
237205.3.16.236/32205.3.16.236 to 205.3.16.236—1
238205.3.16.237/32205.3.16.237 to 205.3.16.237—1
239205.3.16.238/32205.3.16.238 to 205.3.16.238—1
240205.3.16.239/32205.3.16.239 to 205.3.16.239—1
241205.3.16.240/32205.3.16.240 to 205.3.16.240—1
242205.3.16.241/32205.3.16.241 to 205.3.16.241—1
243205.3.16.242/32205.3.16.242 to 205.3.16.242—1
244205.3.16.243/32205.3.16.243 to 205.3.16.243—1
245205.3.16.244/32205.3.16.244 to 205.3.16.244—1
246205.3.16.245/32205.3.16.245 to 205.3.16.245—1
247205.3.16.246/32205.3.16.246 to 205.3.16.246—1
248205.3.16.247/32205.3.16.247 to 205.3.16.247—1
249205.3.16.248/32205.3.16.248 to 205.3.16.248—1
250205.3.16.249/32205.3.16.249 to 205.3.16.249—1
251205.3.16.250/32205.3.16.250 to 205.3.16.250—1
252205.3.16.251/32205.3.16.251 to 205.3.16.251—1
253205.3.16.252/32205.3.16.252 to 205.3.16.252—1
254205.3.16.253/32205.3.16.253 to 205.3.16.253—1
255205.3.16.254/32205.3.16.254 to 205.3.16.254—1
256205.3.16.255/32205.3.16.255 to 205.3.16.255—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.