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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.

Network127.15.128.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
127.15.128.0
Broadcast address
127.15.143.255
First usable
127.15.128.1
Last usable
127.15.143.254
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
Loopback 127.0.0.0/8
This computer
Old class
A (default /8)
As numbers
Hex 7F0F8000 · Integer 2131722240 to 2131726335
Reverse DNS zones
128.15.127.in-addr.arpa
129.15.127.in-addr.arpa
130.15.127.in-addr.arpa
131.15.127.in-addr.arpa
132.15.127.in-addr.arpa
133.15.127.in-addr.arpa
134.15.127.in-addr.arpa
135.15.127.in-addr.arpa
136.15.127.in-addr.arpa
137.15.127.in-addr.arpa
138.15.127.in-addr.arpa
139.15.127.in-addr.arpa
140.15.127.in-addr.arpa
141.15.127.in-addr.arpa
142.15.127.in-addr.arpa
143.15.127.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
Address01111111.00001111.10000000.00000000127.15.128.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network01111111.00001111.10000000.00000000127.15.128.0
Broadcast01111111.00001111.10001111.11111111127.15.143.255
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)

127.15.128.0/20 makes 4,096 subnets of /32; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1127.15.128.0/32127.15.128.0 to 127.15.128.0—1
2127.15.128.1/32127.15.128.1 to 127.15.128.1—1
3127.15.128.2/32127.15.128.2 to 127.15.128.2—1
4127.15.128.3/32127.15.128.3 to 127.15.128.3—1
5127.15.128.4/32127.15.128.4 to 127.15.128.4—1
6127.15.128.5/32127.15.128.5 to 127.15.128.5—1
7127.15.128.6/32127.15.128.6 to 127.15.128.6—1
8127.15.128.7/32127.15.128.7 to 127.15.128.7—1
9127.15.128.8/32127.15.128.8 to 127.15.128.8—1
10127.15.128.9/32127.15.128.9 to 127.15.128.9—1
11127.15.128.10/32127.15.128.10 to 127.15.128.10—1
12127.15.128.11/32127.15.128.11 to 127.15.128.11—1
13127.15.128.12/32127.15.128.12 to 127.15.128.12—1
14127.15.128.13/32127.15.128.13 to 127.15.128.13—1
15127.15.128.14/32127.15.128.14 to 127.15.128.14—1
16127.15.128.15/32127.15.128.15 to 127.15.128.15—1
17127.15.128.16/32127.15.128.16 to 127.15.128.16—1
18127.15.128.17/32127.15.128.17 to 127.15.128.17—1
19127.15.128.18/32127.15.128.18 to 127.15.128.18—1
20127.15.128.19/32127.15.128.19 to 127.15.128.19—1
21127.15.128.20/32127.15.128.20 to 127.15.128.20—1
22127.15.128.21/32127.15.128.21 to 127.15.128.21—1
23127.15.128.22/32127.15.128.22 to 127.15.128.22—1
24127.15.128.23/32127.15.128.23 to 127.15.128.23—1
25127.15.128.24/32127.15.128.24 to 127.15.128.24—1
26127.15.128.25/32127.15.128.25 to 127.15.128.25—1
27127.15.128.26/32127.15.128.26 to 127.15.128.26—1
28127.15.128.27/32127.15.128.27 to 127.15.128.27—1
29127.15.128.28/32127.15.128.28 to 127.15.128.28—1
30127.15.128.29/32127.15.128.29 to 127.15.128.29—1
31127.15.128.30/32127.15.128.30 to 127.15.128.30—1
32127.15.128.31/32127.15.128.31 to 127.15.128.31—1
33127.15.128.32/32127.15.128.32 to 127.15.128.32—1
34127.15.128.33/32127.15.128.33 to 127.15.128.33—1
35127.15.128.34/32127.15.128.34 to 127.15.128.34—1
36127.15.128.35/32127.15.128.35 to 127.15.128.35—1
37127.15.128.36/32127.15.128.36 to 127.15.128.36—1
38127.15.128.37/32127.15.128.37 to 127.15.128.37—1
39127.15.128.38/32127.15.128.38 to 127.15.128.38—1
40127.15.128.39/32127.15.128.39 to 127.15.128.39—1
41127.15.128.40/32127.15.128.40 to 127.15.128.40—1
42127.15.128.41/32127.15.128.41 to 127.15.128.41—1
43127.15.128.42/32127.15.128.42 to 127.15.128.42—1
44127.15.128.43/32127.15.128.43 to 127.15.128.43—1
45127.15.128.44/32127.15.128.44 to 127.15.128.44—1
46127.15.128.45/32127.15.128.45 to 127.15.128.45—1
47127.15.128.46/32127.15.128.46 to 127.15.128.46—1
48127.15.128.47/32127.15.128.47 to 127.15.128.47—1
49127.15.128.48/32127.15.128.48 to 127.15.128.48—1
50127.15.128.49/32127.15.128.49 to 127.15.128.49—1
51127.15.128.50/32127.15.128.50 to 127.15.128.50—1
52127.15.128.51/32127.15.128.51 to 127.15.128.51—1
53127.15.128.52/32127.15.128.52 to 127.15.128.52—1
54127.15.128.53/32127.15.128.53 to 127.15.128.53—1
55127.15.128.54/32127.15.128.54 to 127.15.128.54—1
56127.15.128.55/32127.15.128.55 to 127.15.128.55—1
57127.15.128.56/32127.15.128.56 to 127.15.128.56—1
58127.15.128.57/32127.15.128.57 to 127.15.128.57—1
59127.15.128.58/32127.15.128.58 to 127.15.128.58—1
60127.15.128.59/32127.15.128.59 to 127.15.128.59—1
61127.15.128.60/32127.15.128.60 to 127.15.128.60—1
62127.15.128.61/32127.15.128.61 to 127.15.128.61—1
63127.15.128.62/32127.15.128.62 to 127.15.128.62—1
64127.15.128.63/32127.15.128.63 to 127.15.128.63—1
65127.15.128.64/32127.15.128.64 to 127.15.128.64—1
66127.15.128.65/32127.15.128.65 to 127.15.128.65—1
67127.15.128.66/32127.15.128.66 to 127.15.128.66—1
68127.15.128.67/32127.15.128.67 to 127.15.128.67—1
69127.15.128.68/32127.15.128.68 to 127.15.128.68—1
70127.15.128.69/32127.15.128.69 to 127.15.128.69—1
71127.15.128.70/32127.15.128.70 to 127.15.128.70—1
72127.15.128.71/32127.15.128.71 to 127.15.128.71—1
73127.15.128.72/32127.15.128.72 to 127.15.128.72—1
74127.15.128.73/32127.15.128.73 to 127.15.128.73—1
75127.15.128.74/32127.15.128.74 to 127.15.128.74—1
76127.15.128.75/32127.15.128.75 to 127.15.128.75—1
77127.15.128.76/32127.15.128.76 to 127.15.128.76—1
78127.15.128.77/32127.15.128.77 to 127.15.128.77—1
79127.15.128.78/32127.15.128.78 to 127.15.128.78—1
80127.15.128.79/32127.15.128.79 to 127.15.128.79—1
81127.15.128.80/32127.15.128.80 to 127.15.128.80—1
82127.15.128.81/32127.15.128.81 to 127.15.128.81—1
83127.15.128.82/32127.15.128.82 to 127.15.128.82—1
84127.15.128.83/32127.15.128.83 to 127.15.128.83—1
85127.15.128.84/32127.15.128.84 to 127.15.128.84—1
86127.15.128.85/32127.15.128.85 to 127.15.128.85—1
87127.15.128.86/32127.15.128.86 to 127.15.128.86—1
88127.15.128.87/32127.15.128.87 to 127.15.128.87—1
89127.15.128.88/32127.15.128.88 to 127.15.128.88—1
90127.15.128.89/32127.15.128.89 to 127.15.128.89—1
91127.15.128.90/32127.15.128.90 to 127.15.128.90—1
92127.15.128.91/32127.15.128.91 to 127.15.128.91—1
93127.15.128.92/32127.15.128.92 to 127.15.128.92—1
94127.15.128.93/32127.15.128.93 to 127.15.128.93—1
95127.15.128.94/32127.15.128.94 to 127.15.128.94—1
96127.15.128.95/32127.15.128.95 to 127.15.128.95—1
97127.15.128.96/32127.15.128.96 to 127.15.128.96—1
98127.15.128.97/32127.15.128.97 to 127.15.128.97—1
99127.15.128.98/32127.15.128.98 to 127.15.128.98—1
100127.15.128.99/32127.15.128.99 to 127.15.128.99—1
101127.15.128.100/32127.15.128.100 to 127.15.128.100—1
102127.15.128.101/32127.15.128.101 to 127.15.128.101—1
103127.15.128.102/32127.15.128.102 to 127.15.128.102—1
104127.15.128.103/32127.15.128.103 to 127.15.128.103—1
105127.15.128.104/32127.15.128.104 to 127.15.128.104—1
106127.15.128.105/32127.15.128.105 to 127.15.128.105—1
107127.15.128.106/32127.15.128.106 to 127.15.128.106—1
108127.15.128.107/32127.15.128.107 to 127.15.128.107—1
109127.15.128.108/32127.15.128.108 to 127.15.128.108—1
110127.15.128.109/32127.15.128.109 to 127.15.128.109—1
111127.15.128.110/32127.15.128.110 to 127.15.128.110—1
112127.15.128.111/32127.15.128.111 to 127.15.128.111—1
113127.15.128.112/32127.15.128.112 to 127.15.128.112—1
114127.15.128.113/32127.15.128.113 to 127.15.128.113—1
115127.15.128.114/32127.15.128.114 to 127.15.128.114—1
116127.15.128.115/32127.15.128.115 to 127.15.128.115—1
117127.15.128.116/32127.15.128.116 to 127.15.128.116—1
118127.15.128.117/32127.15.128.117 to 127.15.128.117—1
119127.15.128.118/32127.15.128.118 to 127.15.128.118—1
120127.15.128.119/32127.15.128.119 to 127.15.128.119—1
121127.15.128.120/32127.15.128.120 to 127.15.128.120—1
122127.15.128.121/32127.15.128.121 to 127.15.128.121—1
123127.15.128.122/32127.15.128.122 to 127.15.128.122—1
124127.15.128.123/32127.15.128.123 to 127.15.128.123—1
125127.15.128.124/32127.15.128.124 to 127.15.128.124—1
126127.15.128.125/32127.15.128.125 to 127.15.128.125—1
127127.15.128.126/32127.15.128.126 to 127.15.128.126—1
128127.15.128.127/32127.15.128.127 to 127.15.128.127—1
129127.15.128.128/32127.15.128.128 to 127.15.128.128—1
130127.15.128.129/32127.15.128.129 to 127.15.128.129—1
131127.15.128.130/32127.15.128.130 to 127.15.128.130—1
132127.15.128.131/32127.15.128.131 to 127.15.128.131—1
133127.15.128.132/32127.15.128.132 to 127.15.128.132—1
134127.15.128.133/32127.15.128.133 to 127.15.128.133—1
135127.15.128.134/32127.15.128.134 to 127.15.128.134—1
136127.15.128.135/32127.15.128.135 to 127.15.128.135—1
137127.15.128.136/32127.15.128.136 to 127.15.128.136—1
138127.15.128.137/32127.15.128.137 to 127.15.128.137—1
139127.15.128.138/32127.15.128.138 to 127.15.128.138—1
140127.15.128.139/32127.15.128.139 to 127.15.128.139—1
141127.15.128.140/32127.15.128.140 to 127.15.128.140—1
142127.15.128.141/32127.15.128.141 to 127.15.128.141—1
143127.15.128.142/32127.15.128.142 to 127.15.128.142—1
144127.15.128.143/32127.15.128.143 to 127.15.128.143—1
145127.15.128.144/32127.15.128.144 to 127.15.128.144—1
146127.15.128.145/32127.15.128.145 to 127.15.128.145—1
147127.15.128.146/32127.15.128.146 to 127.15.128.146—1
148127.15.128.147/32127.15.128.147 to 127.15.128.147—1
149127.15.128.148/32127.15.128.148 to 127.15.128.148—1
150127.15.128.149/32127.15.128.149 to 127.15.128.149—1
151127.15.128.150/32127.15.128.150 to 127.15.128.150—1
152127.15.128.151/32127.15.128.151 to 127.15.128.151—1
153127.15.128.152/32127.15.128.152 to 127.15.128.152—1
154127.15.128.153/32127.15.128.153 to 127.15.128.153—1
155127.15.128.154/32127.15.128.154 to 127.15.128.154—1
156127.15.128.155/32127.15.128.155 to 127.15.128.155—1
157127.15.128.156/32127.15.128.156 to 127.15.128.156—1
158127.15.128.157/32127.15.128.157 to 127.15.128.157—1
159127.15.128.158/32127.15.128.158 to 127.15.128.158—1
160127.15.128.159/32127.15.128.159 to 127.15.128.159—1
161127.15.128.160/32127.15.128.160 to 127.15.128.160—1
162127.15.128.161/32127.15.128.161 to 127.15.128.161—1
163127.15.128.162/32127.15.128.162 to 127.15.128.162—1
164127.15.128.163/32127.15.128.163 to 127.15.128.163—1
165127.15.128.164/32127.15.128.164 to 127.15.128.164—1
166127.15.128.165/32127.15.128.165 to 127.15.128.165—1
167127.15.128.166/32127.15.128.166 to 127.15.128.166—1
168127.15.128.167/32127.15.128.167 to 127.15.128.167—1
169127.15.128.168/32127.15.128.168 to 127.15.128.168—1
170127.15.128.169/32127.15.128.169 to 127.15.128.169—1
171127.15.128.170/32127.15.128.170 to 127.15.128.170—1
172127.15.128.171/32127.15.128.171 to 127.15.128.171—1
173127.15.128.172/32127.15.128.172 to 127.15.128.172—1
174127.15.128.173/32127.15.128.173 to 127.15.128.173—1
175127.15.128.174/32127.15.128.174 to 127.15.128.174—1
176127.15.128.175/32127.15.128.175 to 127.15.128.175—1
177127.15.128.176/32127.15.128.176 to 127.15.128.176—1
178127.15.128.177/32127.15.128.177 to 127.15.128.177—1
179127.15.128.178/32127.15.128.178 to 127.15.128.178—1
180127.15.128.179/32127.15.128.179 to 127.15.128.179—1
181127.15.128.180/32127.15.128.180 to 127.15.128.180—1
182127.15.128.181/32127.15.128.181 to 127.15.128.181—1
183127.15.128.182/32127.15.128.182 to 127.15.128.182—1
184127.15.128.183/32127.15.128.183 to 127.15.128.183—1
185127.15.128.184/32127.15.128.184 to 127.15.128.184—1
186127.15.128.185/32127.15.128.185 to 127.15.128.185—1
187127.15.128.186/32127.15.128.186 to 127.15.128.186—1
188127.15.128.187/32127.15.128.187 to 127.15.128.187—1
189127.15.128.188/32127.15.128.188 to 127.15.128.188—1
190127.15.128.189/32127.15.128.189 to 127.15.128.189—1
191127.15.128.190/32127.15.128.190 to 127.15.128.190—1
192127.15.128.191/32127.15.128.191 to 127.15.128.191—1
193127.15.128.192/32127.15.128.192 to 127.15.128.192—1
194127.15.128.193/32127.15.128.193 to 127.15.128.193—1
195127.15.128.194/32127.15.128.194 to 127.15.128.194—1
196127.15.128.195/32127.15.128.195 to 127.15.128.195—1
197127.15.128.196/32127.15.128.196 to 127.15.128.196—1
198127.15.128.197/32127.15.128.197 to 127.15.128.197—1
199127.15.128.198/32127.15.128.198 to 127.15.128.198—1
200127.15.128.199/32127.15.128.199 to 127.15.128.199—1
201127.15.128.200/32127.15.128.200 to 127.15.128.200—1
202127.15.128.201/32127.15.128.201 to 127.15.128.201—1
203127.15.128.202/32127.15.128.202 to 127.15.128.202—1
204127.15.128.203/32127.15.128.203 to 127.15.128.203—1
205127.15.128.204/32127.15.128.204 to 127.15.128.204—1
206127.15.128.205/32127.15.128.205 to 127.15.128.205—1
207127.15.128.206/32127.15.128.206 to 127.15.128.206—1
208127.15.128.207/32127.15.128.207 to 127.15.128.207—1
209127.15.128.208/32127.15.128.208 to 127.15.128.208—1
210127.15.128.209/32127.15.128.209 to 127.15.128.209—1
211127.15.128.210/32127.15.128.210 to 127.15.128.210—1
212127.15.128.211/32127.15.128.211 to 127.15.128.211—1
213127.15.128.212/32127.15.128.212 to 127.15.128.212—1
214127.15.128.213/32127.15.128.213 to 127.15.128.213—1
215127.15.128.214/32127.15.128.214 to 127.15.128.214—1
216127.15.128.215/32127.15.128.215 to 127.15.128.215—1
217127.15.128.216/32127.15.128.216 to 127.15.128.216—1
218127.15.128.217/32127.15.128.217 to 127.15.128.217—1
219127.15.128.218/32127.15.128.218 to 127.15.128.218—1
220127.15.128.219/32127.15.128.219 to 127.15.128.219—1
221127.15.128.220/32127.15.128.220 to 127.15.128.220—1
222127.15.128.221/32127.15.128.221 to 127.15.128.221—1
223127.15.128.222/32127.15.128.222 to 127.15.128.222—1
224127.15.128.223/32127.15.128.223 to 127.15.128.223—1
225127.15.128.224/32127.15.128.224 to 127.15.128.224—1
226127.15.128.225/32127.15.128.225 to 127.15.128.225—1
227127.15.128.226/32127.15.128.226 to 127.15.128.226—1
228127.15.128.227/32127.15.128.227 to 127.15.128.227—1
229127.15.128.228/32127.15.128.228 to 127.15.128.228—1
230127.15.128.229/32127.15.128.229 to 127.15.128.229—1
231127.15.128.230/32127.15.128.230 to 127.15.128.230—1
232127.15.128.231/32127.15.128.231 to 127.15.128.231—1
233127.15.128.232/32127.15.128.232 to 127.15.128.232—1
234127.15.128.233/32127.15.128.233 to 127.15.128.233—1
235127.15.128.234/32127.15.128.234 to 127.15.128.234—1
236127.15.128.235/32127.15.128.235 to 127.15.128.235—1
237127.15.128.236/32127.15.128.236 to 127.15.128.236—1
238127.15.128.237/32127.15.128.237 to 127.15.128.237—1
239127.15.128.238/32127.15.128.238 to 127.15.128.238—1
240127.15.128.239/32127.15.128.239 to 127.15.128.239—1
241127.15.128.240/32127.15.128.240 to 127.15.128.240—1
242127.15.128.241/32127.15.128.241 to 127.15.128.241—1
243127.15.128.242/32127.15.128.242 to 127.15.128.242—1
244127.15.128.243/32127.15.128.243 to 127.15.128.243—1
245127.15.128.244/32127.15.128.244 to 127.15.128.244—1
246127.15.128.245/32127.15.128.245 to 127.15.128.245—1
247127.15.128.246/32127.15.128.246 to 127.15.128.246—1
248127.15.128.247/32127.15.128.247 to 127.15.128.247—1
249127.15.128.248/32127.15.128.248 to 127.15.128.248—1
250127.15.128.249/32127.15.128.249 to 127.15.128.249—1
251127.15.128.250/32127.15.128.250 to 127.15.128.250—1
252127.15.128.251/32127.15.128.251 to 127.15.128.251—1
253127.15.128.252/32127.15.128.252 to 127.15.128.252—1
254127.15.128.253/32127.15.128.253 to 127.15.128.253—1
255127.15.128.254/32127.15.128.254 to 127.15.128.254—1
256127.15.128.255/32127.15.128.255 to 127.15.128.255—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.