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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.

Network124.2.16.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
124.2.16.0
Broadcast address
124.2.31.255
First usable
124.2.16.1
Last usable
124.2.31.254
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
A (default /8)
As numbers
Hex 7C021000 · Integer 2080509952 to 2080514047
Reverse DNS zones
16.2.124.in-addr.arpa
17.2.124.in-addr.arpa
18.2.124.in-addr.arpa
19.2.124.in-addr.arpa
20.2.124.in-addr.arpa
21.2.124.in-addr.arpa
22.2.124.in-addr.arpa
23.2.124.in-addr.arpa
24.2.124.in-addr.arpa
25.2.124.in-addr.arpa
26.2.124.in-addr.arpa
27.2.124.in-addr.arpa
28.2.124.in-addr.arpa
29.2.124.in-addr.arpa
30.2.124.in-addr.arpa
31.2.124.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
Address01111100.00000010.00010000.00000000124.2.16.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network01111100.00000010.00010000.00000000124.2.16.0
Broadcast01111100.00000010.00011111.11111111124.2.31.255
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)

124.2.16.0/20 makes 4,096 subnets of /32; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1124.2.16.0/32124.2.16.0 to 124.2.16.0—1
2124.2.16.1/32124.2.16.1 to 124.2.16.1—1
3124.2.16.2/32124.2.16.2 to 124.2.16.2—1
4124.2.16.3/32124.2.16.3 to 124.2.16.3—1
5124.2.16.4/32124.2.16.4 to 124.2.16.4—1
6124.2.16.5/32124.2.16.5 to 124.2.16.5—1
7124.2.16.6/32124.2.16.6 to 124.2.16.6—1
8124.2.16.7/32124.2.16.7 to 124.2.16.7—1
9124.2.16.8/32124.2.16.8 to 124.2.16.8—1
10124.2.16.9/32124.2.16.9 to 124.2.16.9—1
11124.2.16.10/32124.2.16.10 to 124.2.16.10—1
12124.2.16.11/32124.2.16.11 to 124.2.16.11—1
13124.2.16.12/32124.2.16.12 to 124.2.16.12—1
14124.2.16.13/32124.2.16.13 to 124.2.16.13—1
15124.2.16.14/32124.2.16.14 to 124.2.16.14—1
16124.2.16.15/32124.2.16.15 to 124.2.16.15—1
17124.2.16.16/32124.2.16.16 to 124.2.16.16—1
18124.2.16.17/32124.2.16.17 to 124.2.16.17—1
19124.2.16.18/32124.2.16.18 to 124.2.16.18—1
20124.2.16.19/32124.2.16.19 to 124.2.16.19—1
21124.2.16.20/32124.2.16.20 to 124.2.16.20—1
22124.2.16.21/32124.2.16.21 to 124.2.16.21—1
23124.2.16.22/32124.2.16.22 to 124.2.16.22—1
24124.2.16.23/32124.2.16.23 to 124.2.16.23—1
25124.2.16.24/32124.2.16.24 to 124.2.16.24—1
26124.2.16.25/32124.2.16.25 to 124.2.16.25—1
27124.2.16.26/32124.2.16.26 to 124.2.16.26—1
28124.2.16.27/32124.2.16.27 to 124.2.16.27—1
29124.2.16.28/32124.2.16.28 to 124.2.16.28—1
30124.2.16.29/32124.2.16.29 to 124.2.16.29—1
31124.2.16.30/32124.2.16.30 to 124.2.16.30—1
32124.2.16.31/32124.2.16.31 to 124.2.16.31—1
33124.2.16.32/32124.2.16.32 to 124.2.16.32—1
34124.2.16.33/32124.2.16.33 to 124.2.16.33—1
35124.2.16.34/32124.2.16.34 to 124.2.16.34—1
36124.2.16.35/32124.2.16.35 to 124.2.16.35—1
37124.2.16.36/32124.2.16.36 to 124.2.16.36—1
38124.2.16.37/32124.2.16.37 to 124.2.16.37—1
39124.2.16.38/32124.2.16.38 to 124.2.16.38—1
40124.2.16.39/32124.2.16.39 to 124.2.16.39—1
41124.2.16.40/32124.2.16.40 to 124.2.16.40—1
42124.2.16.41/32124.2.16.41 to 124.2.16.41—1
43124.2.16.42/32124.2.16.42 to 124.2.16.42—1
44124.2.16.43/32124.2.16.43 to 124.2.16.43—1
45124.2.16.44/32124.2.16.44 to 124.2.16.44—1
46124.2.16.45/32124.2.16.45 to 124.2.16.45—1
47124.2.16.46/32124.2.16.46 to 124.2.16.46—1
48124.2.16.47/32124.2.16.47 to 124.2.16.47—1
49124.2.16.48/32124.2.16.48 to 124.2.16.48—1
50124.2.16.49/32124.2.16.49 to 124.2.16.49—1
51124.2.16.50/32124.2.16.50 to 124.2.16.50—1
52124.2.16.51/32124.2.16.51 to 124.2.16.51—1
53124.2.16.52/32124.2.16.52 to 124.2.16.52—1
54124.2.16.53/32124.2.16.53 to 124.2.16.53—1
55124.2.16.54/32124.2.16.54 to 124.2.16.54—1
56124.2.16.55/32124.2.16.55 to 124.2.16.55—1
57124.2.16.56/32124.2.16.56 to 124.2.16.56—1
58124.2.16.57/32124.2.16.57 to 124.2.16.57—1
59124.2.16.58/32124.2.16.58 to 124.2.16.58—1
60124.2.16.59/32124.2.16.59 to 124.2.16.59—1
61124.2.16.60/32124.2.16.60 to 124.2.16.60—1
62124.2.16.61/32124.2.16.61 to 124.2.16.61—1
63124.2.16.62/32124.2.16.62 to 124.2.16.62—1
64124.2.16.63/32124.2.16.63 to 124.2.16.63—1
65124.2.16.64/32124.2.16.64 to 124.2.16.64—1
66124.2.16.65/32124.2.16.65 to 124.2.16.65—1
67124.2.16.66/32124.2.16.66 to 124.2.16.66—1
68124.2.16.67/32124.2.16.67 to 124.2.16.67—1
69124.2.16.68/32124.2.16.68 to 124.2.16.68—1
70124.2.16.69/32124.2.16.69 to 124.2.16.69—1
71124.2.16.70/32124.2.16.70 to 124.2.16.70—1
72124.2.16.71/32124.2.16.71 to 124.2.16.71—1
73124.2.16.72/32124.2.16.72 to 124.2.16.72—1
74124.2.16.73/32124.2.16.73 to 124.2.16.73—1
75124.2.16.74/32124.2.16.74 to 124.2.16.74—1
76124.2.16.75/32124.2.16.75 to 124.2.16.75—1
77124.2.16.76/32124.2.16.76 to 124.2.16.76—1
78124.2.16.77/32124.2.16.77 to 124.2.16.77—1
79124.2.16.78/32124.2.16.78 to 124.2.16.78—1
80124.2.16.79/32124.2.16.79 to 124.2.16.79—1
81124.2.16.80/32124.2.16.80 to 124.2.16.80—1
82124.2.16.81/32124.2.16.81 to 124.2.16.81—1
83124.2.16.82/32124.2.16.82 to 124.2.16.82—1
84124.2.16.83/32124.2.16.83 to 124.2.16.83—1
85124.2.16.84/32124.2.16.84 to 124.2.16.84—1
86124.2.16.85/32124.2.16.85 to 124.2.16.85—1
87124.2.16.86/32124.2.16.86 to 124.2.16.86—1
88124.2.16.87/32124.2.16.87 to 124.2.16.87—1
89124.2.16.88/32124.2.16.88 to 124.2.16.88—1
90124.2.16.89/32124.2.16.89 to 124.2.16.89—1
91124.2.16.90/32124.2.16.90 to 124.2.16.90—1
92124.2.16.91/32124.2.16.91 to 124.2.16.91—1
93124.2.16.92/32124.2.16.92 to 124.2.16.92—1
94124.2.16.93/32124.2.16.93 to 124.2.16.93—1
95124.2.16.94/32124.2.16.94 to 124.2.16.94—1
96124.2.16.95/32124.2.16.95 to 124.2.16.95—1
97124.2.16.96/32124.2.16.96 to 124.2.16.96—1
98124.2.16.97/32124.2.16.97 to 124.2.16.97—1
99124.2.16.98/32124.2.16.98 to 124.2.16.98—1
100124.2.16.99/32124.2.16.99 to 124.2.16.99—1
101124.2.16.100/32124.2.16.100 to 124.2.16.100—1
102124.2.16.101/32124.2.16.101 to 124.2.16.101—1
103124.2.16.102/32124.2.16.102 to 124.2.16.102—1
104124.2.16.103/32124.2.16.103 to 124.2.16.103—1
105124.2.16.104/32124.2.16.104 to 124.2.16.104—1
106124.2.16.105/32124.2.16.105 to 124.2.16.105—1
107124.2.16.106/32124.2.16.106 to 124.2.16.106—1
108124.2.16.107/32124.2.16.107 to 124.2.16.107—1
109124.2.16.108/32124.2.16.108 to 124.2.16.108—1
110124.2.16.109/32124.2.16.109 to 124.2.16.109—1
111124.2.16.110/32124.2.16.110 to 124.2.16.110—1
112124.2.16.111/32124.2.16.111 to 124.2.16.111—1
113124.2.16.112/32124.2.16.112 to 124.2.16.112—1
114124.2.16.113/32124.2.16.113 to 124.2.16.113—1
115124.2.16.114/32124.2.16.114 to 124.2.16.114—1
116124.2.16.115/32124.2.16.115 to 124.2.16.115—1
117124.2.16.116/32124.2.16.116 to 124.2.16.116—1
118124.2.16.117/32124.2.16.117 to 124.2.16.117—1
119124.2.16.118/32124.2.16.118 to 124.2.16.118—1
120124.2.16.119/32124.2.16.119 to 124.2.16.119—1
121124.2.16.120/32124.2.16.120 to 124.2.16.120—1
122124.2.16.121/32124.2.16.121 to 124.2.16.121—1
123124.2.16.122/32124.2.16.122 to 124.2.16.122—1
124124.2.16.123/32124.2.16.123 to 124.2.16.123—1
125124.2.16.124/32124.2.16.124 to 124.2.16.124—1
126124.2.16.125/32124.2.16.125 to 124.2.16.125—1
127124.2.16.126/32124.2.16.126 to 124.2.16.126—1
128124.2.16.127/32124.2.16.127 to 124.2.16.127—1
129124.2.16.128/32124.2.16.128 to 124.2.16.128—1
130124.2.16.129/32124.2.16.129 to 124.2.16.129—1
131124.2.16.130/32124.2.16.130 to 124.2.16.130—1
132124.2.16.131/32124.2.16.131 to 124.2.16.131—1
133124.2.16.132/32124.2.16.132 to 124.2.16.132—1
134124.2.16.133/32124.2.16.133 to 124.2.16.133—1
135124.2.16.134/32124.2.16.134 to 124.2.16.134—1
136124.2.16.135/32124.2.16.135 to 124.2.16.135—1
137124.2.16.136/32124.2.16.136 to 124.2.16.136—1
138124.2.16.137/32124.2.16.137 to 124.2.16.137—1
139124.2.16.138/32124.2.16.138 to 124.2.16.138—1
140124.2.16.139/32124.2.16.139 to 124.2.16.139—1
141124.2.16.140/32124.2.16.140 to 124.2.16.140—1
142124.2.16.141/32124.2.16.141 to 124.2.16.141—1
143124.2.16.142/32124.2.16.142 to 124.2.16.142—1
144124.2.16.143/32124.2.16.143 to 124.2.16.143—1
145124.2.16.144/32124.2.16.144 to 124.2.16.144—1
146124.2.16.145/32124.2.16.145 to 124.2.16.145—1
147124.2.16.146/32124.2.16.146 to 124.2.16.146—1
148124.2.16.147/32124.2.16.147 to 124.2.16.147—1
149124.2.16.148/32124.2.16.148 to 124.2.16.148—1
150124.2.16.149/32124.2.16.149 to 124.2.16.149—1
151124.2.16.150/32124.2.16.150 to 124.2.16.150—1
152124.2.16.151/32124.2.16.151 to 124.2.16.151—1
153124.2.16.152/32124.2.16.152 to 124.2.16.152—1
154124.2.16.153/32124.2.16.153 to 124.2.16.153—1
155124.2.16.154/32124.2.16.154 to 124.2.16.154—1
156124.2.16.155/32124.2.16.155 to 124.2.16.155—1
157124.2.16.156/32124.2.16.156 to 124.2.16.156—1
158124.2.16.157/32124.2.16.157 to 124.2.16.157—1
159124.2.16.158/32124.2.16.158 to 124.2.16.158—1
160124.2.16.159/32124.2.16.159 to 124.2.16.159—1
161124.2.16.160/32124.2.16.160 to 124.2.16.160—1
162124.2.16.161/32124.2.16.161 to 124.2.16.161—1
163124.2.16.162/32124.2.16.162 to 124.2.16.162—1
164124.2.16.163/32124.2.16.163 to 124.2.16.163—1
165124.2.16.164/32124.2.16.164 to 124.2.16.164—1
166124.2.16.165/32124.2.16.165 to 124.2.16.165—1
167124.2.16.166/32124.2.16.166 to 124.2.16.166—1
168124.2.16.167/32124.2.16.167 to 124.2.16.167—1
169124.2.16.168/32124.2.16.168 to 124.2.16.168—1
170124.2.16.169/32124.2.16.169 to 124.2.16.169—1
171124.2.16.170/32124.2.16.170 to 124.2.16.170—1
172124.2.16.171/32124.2.16.171 to 124.2.16.171—1
173124.2.16.172/32124.2.16.172 to 124.2.16.172—1
174124.2.16.173/32124.2.16.173 to 124.2.16.173—1
175124.2.16.174/32124.2.16.174 to 124.2.16.174—1
176124.2.16.175/32124.2.16.175 to 124.2.16.175—1
177124.2.16.176/32124.2.16.176 to 124.2.16.176—1
178124.2.16.177/32124.2.16.177 to 124.2.16.177—1
179124.2.16.178/32124.2.16.178 to 124.2.16.178—1
180124.2.16.179/32124.2.16.179 to 124.2.16.179—1
181124.2.16.180/32124.2.16.180 to 124.2.16.180—1
182124.2.16.181/32124.2.16.181 to 124.2.16.181—1
183124.2.16.182/32124.2.16.182 to 124.2.16.182—1
184124.2.16.183/32124.2.16.183 to 124.2.16.183—1
185124.2.16.184/32124.2.16.184 to 124.2.16.184—1
186124.2.16.185/32124.2.16.185 to 124.2.16.185—1
187124.2.16.186/32124.2.16.186 to 124.2.16.186—1
188124.2.16.187/32124.2.16.187 to 124.2.16.187—1
189124.2.16.188/32124.2.16.188 to 124.2.16.188—1
190124.2.16.189/32124.2.16.189 to 124.2.16.189—1
191124.2.16.190/32124.2.16.190 to 124.2.16.190—1
192124.2.16.191/32124.2.16.191 to 124.2.16.191—1
193124.2.16.192/32124.2.16.192 to 124.2.16.192—1
194124.2.16.193/32124.2.16.193 to 124.2.16.193—1
195124.2.16.194/32124.2.16.194 to 124.2.16.194—1
196124.2.16.195/32124.2.16.195 to 124.2.16.195—1
197124.2.16.196/32124.2.16.196 to 124.2.16.196—1
198124.2.16.197/32124.2.16.197 to 124.2.16.197—1
199124.2.16.198/32124.2.16.198 to 124.2.16.198—1
200124.2.16.199/32124.2.16.199 to 124.2.16.199—1
201124.2.16.200/32124.2.16.200 to 124.2.16.200—1
202124.2.16.201/32124.2.16.201 to 124.2.16.201—1
203124.2.16.202/32124.2.16.202 to 124.2.16.202—1
204124.2.16.203/32124.2.16.203 to 124.2.16.203—1
205124.2.16.204/32124.2.16.204 to 124.2.16.204—1
206124.2.16.205/32124.2.16.205 to 124.2.16.205—1
207124.2.16.206/32124.2.16.206 to 124.2.16.206—1
208124.2.16.207/32124.2.16.207 to 124.2.16.207—1
209124.2.16.208/32124.2.16.208 to 124.2.16.208—1
210124.2.16.209/32124.2.16.209 to 124.2.16.209—1
211124.2.16.210/32124.2.16.210 to 124.2.16.210—1
212124.2.16.211/32124.2.16.211 to 124.2.16.211—1
213124.2.16.212/32124.2.16.212 to 124.2.16.212—1
214124.2.16.213/32124.2.16.213 to 124.2.16.213—1
215124.2.16.214/32124.2.16.214 to 124.2.16.214—1
216124.2.16.215/32124.2.16.215 to 124.2.16.215—1
217124.2.16.216/32124.2.16.216 to 124.2.16.216—1
218124.2.16.217/32124.2.16.217 to 124.2.16.217—1
219124.2.16.218/32124.2.16.218 to 124.2.16.218—1
220124.2.16.219/32124.2.16.219 to 124.2.16.219—1
221124.2.16.220/32124.2.16.220 to 124.2.16.220—1
222124.2.16.221/32124.2.16.221 to 124.2.16.221—1
223124.2.16.222/32124.2.16.222 to 124.2.16.222—1
224124.2.16.223/32124.2.16.223 to 124.2.16.223—1
225124.2.16.224/32124.2.16.224 to 124.2.16.224—1
226124.2.16.225/32124.2.16.225 to 124.2.16.225—1
227124.2.16.226/32124.2.16.226 to 124.2.16.226—1
228124.2.16.227/32124.2.16.227 to 124.2.16.227—1
229124.2.16.228/32124.2.16.228 to 124.2.16.228—1
230124.2.16.229/32124.2.16.229 to 124.2.16.229—1
231124.2.16.230/32124.2.16.230 to 124.2.16.230—1
232124.2.16.231/32124.2.16.231 to 124.2.16.231—1
233124.2.16.232/32124.2.16.232 to 124.2.16.232—1
234124.2.16.233/32124.2.16.233 to 124.2.16.233—1
235124.2.16.234/32124.2.16.234 to 124.2.16.234—1
236124.2.16.235/32124.2.16.235 to 124.2.16.235—1
237124.2.16.236/32124.2.16.236 to 124.2.16.236—1
238124.2.16.237/32124.2.16.237 to 124.2.16.237—1
239124.2.16.238/32124.2.16.238 to 124.2.16.238—1
240124.2.16.239/32124.2.16.239 to 124.2.16.239—1
241124.2.16.240/32124.2.16.240 to 124.2.16.240—1
242124.2.16.241/32124.2.16.241 to 124.2.16.241—1
243124.2.16.242/32124.2.16.242 to 124.2.16.242—1
244124.2.16.243/32124.2.16.243 to 124.2.16.243—1
245124.2.16.244/32124.2.16.244 to 124.2.16.244—1
246124.2.16.245/32124.2.16.245 to 124.2.16.245—1
247124.2.16.246/32124.2.16.246 to 124.2.16.246—1
248124.2.16.247/32124.2.16.247 to 124.2.16.247—1
249124.2.16.248/32124.2.16.248 to 124.2.16.248—1
250124.2.16.249/32124.2.16.249 to 124.2.16.249—1
251124.2.16.250/32124.2.16.250 to 124.2.16.250—1
252124.2.16.251/32124.2.16.251 to 124.2.16.251—1
253124.2.16.252/32124.2.16.252 to 124.2.16.252—1
254124.2.16.253/32124.2.16.253 to 124.2.16.253—1
255124.2.16.254/32124.2.16.254 to 124.2.16.254—1
256124.2.16.255/32124.2.16.255 to 124.2.16.255—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.