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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.

Network192.168.72.0/21
Usable hosts2,046
Subnet mask255.255.248.0
Addresses2,048
Network address
192.168.72.0
Broadcast address
192.168.79.255
First usable
192.168.72.1
Last usable
192.168.79.254
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
Private (RFC 1918) 192.168.0.0/16
Office and home networks; not routed on the internet
Old class
C (default /24)
As numbers
Hex C0A84800 · Integer 3232253952 to 3232255999
Reverse DNS zones
72.168.192.in-addr.arpa
73.168.192.in-addr.arpa
74.168.192.in-addr.arpa
75.168.192.in-addr.arpa
76.168.192.in-addr.arpa
77.168.192.in-addr.arpa
78.168.192.in-addr.arpa
79.168.192.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
Address11000000.10101000.01001000.00000000192.168.72.0
Subnet mask11111111.11111111.11111000.00000000255.255.248.0
Network11000000.10101000.01001000.00000000192.168.72.0
Broadcast11000000.10101000.01001111.11111111192.168.79.255
Split into smaller subnets/31
/22 (2)/23 (4)/24 (8)/25 (16)/26 (32)/27 (64)/28 (128)/29 (256)/30 (512)/31 (1,024)/32 (2,048)

192.168.72.0/21 makes 1,024 subnets of /31; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1192.168.72.0/31192.168.72.0 to 192.168.72.1—2
2192.168.72.2/31192.168.72.2 to 192.168.72.3—2
3192.168.72.4/31192.168.72.4 to 192.168.72.5—2
4192.168.72.6/31192.168.72.6 to 192.168.72.7—2
5192.168.72.8/31192.168.72.8 to 192.168.72.9—2
6192.168.72.10/31192.168.72.10 to 192.168.72.11—2
7192.168.72.12/31192.168.72.12 to 192.168.72.13—2
8192.168.72.14/31192.168.72.14 to 192.168.72.15—2
9192.168.72.16/31192.168.72.16 to 192.168.72.17—2
10192.168.72.18/31192.168.72.18 to 192.168.72.19—2
11192.168.72.20/31192.168.72.20 to 192.168.72.21—2
12192.168.72.22/31192.168.72.22 to 192.168.72.23—2
13192.168.72.24/31192.168.72.24 to 192.168.72.25—2
14192.168.72.26/31192.168.72.26 to 192.168.72.27—2
15192.168.72.28/31192.168.72.28 to 192.168.72.29—2
16192.168.72.30/31192.168.72.30 to 192.168.72.31—2
17192.168.72.32/31192.168.72.32 to 192.168.72.33—2
18192.168.72.34/31192.168.72.34 to 192.168.72.35—2
19192.168.72.36/31192.168.72.36 to 192.168.72.37—2
20192.168.72.38/31192.168.72.38 to 192.168.72.39—2
21192.168.72.40/31192.168.72.40 to 192.168.72.41—2
22192.168.72.42/31192.168.72.42 to 192.168.72.43—2
23192.168.72.44/31192.168.72.44 to 192.168.72.45—2
24192.168.72.46/31192.168.72.46 to 192.168.72.47—2
25192.168.72.48/31192.168.72.48 to 192.168.72.49—2
26192.168.72.50/31192.168.72.50 to 192.168.72.51—2
27192.168.72.52/31192.168.72.52 to 192.168.72.53—2
28192.168.72.54/31192.168.72.54 to 192.168.72.55—2
29192.168.72.56/31192.168.72.56 to 192.168.72.57—2
30192.168.72.58/31192.168.72.58 to 192.168.72.59—2
31192.168.72.60/31192.168.72.60 to 192.168.72.61—2
32192.168.72.62/31192.168.72.62 to 192.168.72.63—2
33192.168.72.64/31192.168.72.64 to 192.168.72.65—2
34192.168.72.66/31192.168.72.66 to 192.168.72.67—2
35192.168.72.68/31192.168.72.68 to 192.168.72.69—2
36192.168.72.70/31192.168.72.70 to 192.168.72.71—2
37192.168.72.72/31192.168.72.72 to 192.168.72.73—2
38192.168.72.74/31192.168.72.74 to 192.168.72.75—2
39192.168.72.76/31192.168.72.76 to 192.168.72.77—2
40192.168.72.78/31192.168.72.78 to 192.168.72.79—2
41192.168.72.80/31192.168.72.80 to 192.168.72.81—2
42192.168.72.82/31192.168.72.82 to 192.168.72.83—2
43192.168.72.84/31192.168.72.84 to 192.168.72.85—2
44192.168.72.86/31192.168.72.86 to 192.168.72.87—2
45192.168.72.88/31192.168.72.88 to 192.168.72.89—2
46192.168.72.90/31192.168.72.90 to 192.168.72.91—2
47192.168.72.92/31192.168.72.92 to 192.168.72.93—2
48192.168.72.94/31192.168.72.94 to 192.168.72.95—2
49192.168.72.96/31192.168.72.96 to 192.168.72.97—2
50192.168.72.98/31192.168.72.98 to 192.168.72.99—2
51192.168.72.100/31192.168.72.100 to 192.168.72.101—2
52192.168.72.102/31192.168.72.102 to 192.168.72.103—2
53192.168.72.104/31192.168.72.104 to 192.168.72.105—2
54192.168.72.106/31192.168.72.106 to 192.168.72.107—2
55192.168.72.108/31192.168.72.108 to 192.168.72.109—2
56192.168.72.110/31192.168.72.110 to 192.168.72.111—2
57192.168.72.112/31192.168.72.112 to 192.168.72.113—2
58192.168.72.114/31192.168.72.114 to 192.168.72.115—2
59192.168.72.116/31192.168.72.116 to 192.168.72.117—2
60192.168.72.118/31192.168.72.118 to 192.168.72.119—2
61192.168.72.120/31192.168.72.120 to 192.168.72.121—2
62192.168.72.122/31192.168.72.122 to 192.168.72.123—2
63192.168.72.124/31192.168.72.124 to 192.168.72.125—2
64192.168.72.126/31192.168.72.126 to 192.168.72.127—2
65192.168.72.128/31192.168.72.128 to 192.168.72.129—2
66192.168.72.130/31192.168.72.130 to 192.168.72.131—2
67192.168.72.132/31192.168.72.132 to 192.168.72.133—2
68192.168.72.134/31192.168.72.134 to 192.168.72.135—2
69192.168.72.136/31192.168.72.136 to 192.168.72.137—2
70192.168.72.138/31192.168.72.138 to 192.168.72.139—2
71192.168.72.140/31192.168.72.140 to 192.168.72.141—2
72192.168.72.142/31192.168.72.142 to 192.168.72.143—2
73192.168.72.144/31192.168.72.144 to 192.168.72.145—2
74192.168.72.146/31192.168.72.146 to 192.168.72.147—2
75192.168.72.148/31192.168.72.148 to 192.168.72.149—2
76192.168.72.150/31192.168.72.150 to 192.168.72.151—2
77192.168.72.152/31192.168.72.152 to 192.168.72.153—2
78192.168.72.154/31192.168.72.154 to 192.168.72.155—2
79192.168.72.156/31192.168.72.156 to 192.168.72.157—2
80192.168.72.158/31192.168.72.158 to 192.168.72.159—2
81192.168.72.160/31192.168.72.160 to 192.168.72.161—2
82192.168.72.162/31192.168.72.162 to 192.168.72.163—2
83192.168.72.164/31192.168.72.164 to 192.168.72.165—2
84192.168.72.166/31192.168.72.166 to 192.168.72.167—2
85192.168.72.168/31192.168.72.168 to 192.168.72.169—2
86192.168.72.170/31192.168.72.170 to 192.168.72.171—2
87192.168.72.172/31192.168.72.172 to 192.168.72.173—2
88192.168.72.174/31192.168.72.174 to 192.168.72.175—2
89192.168.72.176/31192.168.72.176 to 192.168.72.177—2
90192.168.72.178/31192.168.72.178 to 192.168.72.179—2
91192.168.72.180/31192.168.72.180 to 192.168.72.181—2
92192.168.72.182/31192.168.72.182 to 192.168.72.183—2
93192.168.72.184/31192.168.72.184 to 192.168.72.185—2
94192.168.72.186/31192.168.72.186 to 192.168.72.187—2
95192.168.72.188/31192.168.72.188 to 192.168.72.189—2
96192.168.72.190/31192.168.72.190 to 192.168.72.191—2
97192.168.72.192/31192.168.72.192 to 192.168.72.193—2
98192.168.72.194/31192.168.72.194 to 192.168.72.195—2
99192.168.72.196/31192.168.72.196 to 192.168.72.197—2
100192.168.72.198/31192.168.72.198 to 192.168.72.199—2
101192.168.72.200/31192.168.72.200 to 192.168.72.201—2
102192.168.72.202/31192.168.72.202 to 192.168.72.203—2
103192.168.72.204/31192.168.72.204 to 192.168.72.205—2
104192.168.72.206/31192.168.72.206 to 192.168.72.207—2
105192.168.72.208/31192.168.72.208 to 192.168.72.209—2
106192.168.72.210/31192.168.72.210 to 192.168.72.211—2
107192.168.72.212/31192.168.72.212 to 192.168.72.213—2
108192.168.72.214/31192.168.72.214 to 192.168.72.215—2
109192.168.72.216/31192.168.72.216 to 192.168.72.217—2
110192.168.72.218/31192.168.72.218 to 192.168.72.219—2
111192.168.72.220/31192.168.72.220 to 192.168.72.221—2
112192.168.72.222/31192.168.72.222 to 192.168.72.223—2
113192.168.72.224/31192.168.72.224 to 192.168.72.225—2
114192.168.72.226/31192.168.72.226 to 192.168.72.227—2
115192.168.72.228/31192.168.72.228 to 192.168.72.229—2
116192.168.72.230/31192.168.72.230 to 192.168.72.231—2
117192.168.72.232/31192.168.72.232 to 192.168.72.233—2
118192.168.72.234/31192.168.72.234 to 192.168.72.235—2
119192.168.72.236/31192.168.72.236 to 192.168.72.237—2
120192.168.72.238/31192.168.72.238 to 192.168.72.239—2
121192.168.72.240/31192.168.72.240 to 192.168.72.241—2
122192.168.72.242/31192.168.72.242 to 192.168.72.243—2
123192.168.72.244/31192.168.72.244 to 192.168.72.245—2
124192.168.72.246/31192.168.72.246 to 192.168.72.247—2
125192.168.72.248/31192.168.72.248 to 192.168.72.249—2
126192.168.72.250/31192.168.72.250 to 192.168.72.251—2
127192.168.72.252/31192.168.72.252 to 192.168.72.253—2
128192.168.72.254/31192.168.72.254 to 192.168.72.255—2
129192.168.73.0/31192.168.73.0 to 192.168.73.1—2
130192.168.73.2/31192.168.73.2 to 192.168.73.3—2
131192.168.73.4/31192.168.73.4 to 192.168.73.5—2
132192.168.73.6/31192.168.73.6 to 192.168.73.7—2
133192.168.73.8/31192.168.73.8 to 192.168.73.9—2
134192.168.73.10/31192.168.73.10 to 192.168.73.11—2
135192.168.73.12/31192.168.73.12 to 192.168.73.13—2
136192.168.73.14/31192.168.73.14 to 192.168.73.15—2
137192.168.73.16/31192.168.73.16 to 192.168.73.17—2
138192.168.73.18/31192.168.73.18 to 192.168.73.19—2
139192.168.73.20/31192.168.73.20 to 192.168.73.21—2
140192.168.73.22/31192.168.73.22 to 192.168.73.23—2
141192.168.73.24/31192.168.73.24 to 192.168.73.25—2
142192.168.73.26/31192.168.73.26 to 192.168.73.27—2
143192.168.73.28/31192.168.73.28 to 192.168.73.29—2
144192.168.73.30/31192.168.73.30 to 192.168.73.31—2
145192.168.73.32/31192.168.73.32 to 192.168.73.33—2
146192.168.73.34/31192.168.73.34 to 192.168.73.35—2
147192.168.73.36/31192.168.73.36 to 192.168.73.37—2
148192.168.73.38/31192.168.73.38 to 192.168.73.39—2
149192.168.73.40/31192.168.73.40 to 192.168.73.41—2
150192.168.73.42/31192.168.73.42 to 192.168.73.43—2
151192.168.73.44/31192.168.73.44 to 192.168.73.45—2
152192.168.73.46/31192.168.73.46 to 192.168.73.47—2
153192.168.73.48/31192.168.73.48 to 192.168.73.49—2
154192.168.73.50/31192.168.73.50 to 192.168.73.51—2
155192.168.73.52/31192.168.73.52 to 192.168.73.53—2
156192.168.73.54/31192.168.73.54 to 192.168.73.55—2
157192.168.73.56/31192.168.73.56 to 192.168.73.57—2
158192.168.73.58/31192.168.73.58 to 192.168.73.59—2
159192.168.73.60/31192.168.73.60 to 192.168.73.61—2
160192.168.73.62/31192.168.73.62 to 192.168.73.63—2
161192.168.73.64/31192.168.73.64 to 192.168.73.65—2
162192.168.73.66/31192.168.73.66 to 192.168.73.67—2
163192.168.73.68/31192.168.73.68 to 192.168.73.69—2
164192.168.73.70/31192.168.73.70 to 192.168.73.71—2
165192.168.73.72/31192.168.73.72 to 192.168.73.73—2
166192.168.73.74/31192.168.73.74 to 192.168.73.75—2
167192.168.73.76/31192.168.73.76 to 192.168.73.77—2
168192.168.73.78/31192.168.73.78 to 192.168.73.79—2
169192.168.73.80/31192.168.73.80 to 192.168.73.81—2
170192.168.73.82/31192.168.73.82 to 192.168.73.83—2
171192.168.73.84/31192.168.73.84 to 192.168.73.85—2
172192.168.73.86/31192.168.73.86 to 192.168.73.87—2
173192.168.73.88/31192.168.73.88 to 192.168.73.89—2
174192.168.73.90/31192.168.73.90 to 192.168.73.91—2
175192.168.73.92/31192.168.73.92 to 192.168.73.93—2
176192.168.73.94/31192.168.73.94 to 192.168.73.95—2
177192.168.73.96/31192.168.73.96 to 192.168.73.97—2
178192.168.73.98/31192.168.73.98 to 192.168.73.99—2
179192.168.73.100/31192.168.73.100 to 192.168.73.101—2
180192.168.73.102/31192.168.73.102 to 192.168.73.103—2
181192.168.73.104/31192.168.73.104 to 192.168.73.105—2
182192.168.73.106/31192.168.73.106 to 192.168.73.107—2
183192.168.73.108/31192.168.73.108 to 192.168.73.109—2
184192.168.73.110/31192.168.73.110 to 192.168.73.111—2
185192.168.73.112/31192.168.73.112 to 192.168.73.113—2
186192.168.73.114/31192.168.73.114 to 192.168.73.115—2
187192.168.73.116/31192.168.73.116 to 192.168.73.117—2
188192.168.73.118/31192.168.73.118 to 192.168.73.119—2
189192.168.73.120/31192.168.73.120 to 192.168.73.121—2
190192.168.73.122/31192.168.73.122 to 192.168.73.123—2
191192.168.73.124/31192.168.73.124 to 192.168.73.125—2
192192.168.73.126/31192.168.73.126 to 192.168.73.127—2
193192.168.73.128/31192.168.73.128 to 192.168.73.129—2
194192.168.73.130/31192.168.73.130 to 192.168.73.131—2
195192.168.73.132/31192.168.73.132 to 192.168.73.133—2
196192.168.73.134/31192.168.73.134 to 192.168.73.135—2
197192.168.73.136/31192.168.73.136 to 192.168.73.137—2
198192.168.73.138/31192.168.73.138 to 192.168.73.139—2
199192.168.73.140/31192.168.73.140 to 192.168.73.141—2
200192.168.73.142/31192.168.73.142 to 192.168.73.143—2
201192.168.73.144/31192.168.73.144 to 192.168.73.145—2
202192.168.73.146/31192.168.73.146 to 192.168.73.147—2
203192.168.73.148/31192.168.73.148 to 192.168.73.149—2
204192.168.73.150/31192.168.73.150 to 192.168.73.151—2
205192.168.73.152/31192.168.73.152 to 192.168.73.153—2
206192.168.73.154/31192.168.73.154 to 192.168.73.155—2
207192.168.73.156/31192.168.73.156 to 192.168.73.157—2
208192.168.73.158/31192.168.73.158 to 192.168.73.159—2
209192.168.73.160/31192.168.73.160 to 192.168.73.161—2
210192.168.73.162/31192.168.73.162 to 192.168.73.163—2
211192.168.73.164/31192.168.73.164 to 192.168.73.165—2
212192.168.73.166/31192.168.73.166 to 192.168.73.167—2
213192.168.73.168/31192.168.73.168 to 192.168.73.169—2
214192.168.73.170/31192.168.73.170 to 192.168.73.171—2
215192.168.73.172/31192.168.73.172 to 192.168.73.173—2
216192.168.73.174/31192.168.73.174 to 192.168.73.175—2
217192.168.73.176/31192.168.73.176 to 192.168.73.177—2
218192.168.73.178/31192.168.73.178 to 192.168.73.179—2
219192.168.73.180/31192.168.73.180 to 192.168.73.181—2
220192.168.73.182/31192.168.73.182 to 192.168.73.183—2
221192.168.73.184/31192.168.73.184 to 192.168.73.185—2
222192.168.73.186/31192.168.73.186 to 192.168.73.187—2
223192.168.73.188/31192.168.73.188 to 192.168.73.189—2
224192.168.73.190/31192.168.73.190 to 192.168.73.191—2
225192.168.73.192/31192.168.73.192 to 192.168.73.193—2
226192.168.73.194/31192.168.73.194 to 192.168.73.195—2
227192.168.73.196/31192.168.73.196 to 192.168.73.197—2
228192.168.73.198/31192.168.73.198 to 192.168.73.199—2
229192.168.73.200/31192.168.73.200 to 192.168.73.201—2
230192.168.73.202/31192.168.73.202 to 192.168.73.203—2
231192.168.73.204/31192.168.73.204 to 192.168.73.205—2
232192.168.73.206/31192.168.73.206 to 192.168.73.207—2
233192.168.73.208/31192.168.73.208 to 192.168.73.209—2
234192.168.73.210/31192.168.73.210 to 192.168.73.211—2
235192.168.73.212/31192.168.73.212 to 192.168.73.213—2
236192.168.73.214/31192.168.73.214 to 192.168.73.215—2
237192.168.73.216/31192.168.73.216 to 192.168.73.217—2
238192.168.73.218/31192.168.73.218 to 192.168.73.219—2
239192.168.73.220/31192.168.73.220 to 192.168.73.221—2
240192.168.73.222/31192.168.73.222 to 192.168.73.223—2
241192.168.73.224/31192.168.73.224 to 192.168.73.225—2
242192.168.73.226/31192.168.73.226 to 192.168.73.227—2
243192.168.73.228/31192.168.73.228 to 192.168.73.229—2
244192.168.73.230/31192.168.73.230 to 192.168.73.231—2
245192.168.73.232/31192.168.73.232 to 192.168.73.233—2
246192.168.73.234/31192.168.73.234 to 192.168.73.235—2
247192.168.73.236/31192.168.73.236 to 192.168.73.237—2
248192.168.73.238/31192.168.73.238 to 192.168.73.239—2
249192.168.73.240/31192.168.73.240 to 192.168.73.241—2
250192.168.73.242/31192.168.73.242 to 192.168.73.243—2
251192.168.73.244/31192.168.73.244 to 192.168.73.245—2
252192.168.73.246/31192.168.73.246 to 192.168.73.247—2
253192.168.73.248/31192.168.73.248 to 192.168.73.249—2
254192.168.73.250/31192.168.73.250 to 192.168.73.251—2
255192.168.73.252/31192.168.73.252 to 192.168.73.253—2
256192.168.73.254/31192.168.73.254 to 192.168.73.255—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.