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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.

Network187.4.16.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
187.4.16.0
Broadcast address
187.4.31.255
First usable
187.4.16.1
Last usable
187.4.31.254
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
B (default /16)
As numbers
Hex BB041000 · Integer 3137605632 to 3137609727
Reverse DNS zones
16.4.187.in-addr.arpa
17.4.187.in-addr.arpa
18.4.187.in-addr.arpa
19.4.187.in-addr.arpa
20.4.187.in-addr.arpa
21.4.187.in-addr.arpa
22.4.187.in-addr.arpa
23.4.187.in-addr.arpa
24.4.187.in-addr.arpa
25.4.187.in-addr.arpa
26.4.187.in-addr.arpa
27.4.187.in-addr.arpa
28.4.187.in-addr.arpa
29.4.187.in-addr.arpa
30.4.187.in-addr.arpa
31.4.187.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
Address10111011.00000100.00010000.00000000187.4.16.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network10111011.00000100.00010000.00000000187.4.16.0
Broadcast10111011.00000100.00011111.11111111187.4.31.255
Split into smaller subnets/30
/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)

187.4.16.0/20 makes 1,024 subnets of /30; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1187.4.16.0/30187.4.16.1 to 187.4.16.2187.4.16.32
2187.4.16.4/30187.4.16.5 to 187.4.16.6187.4.16.72
3187.4.16.8/30187.4.16.9 to 187.4.16.10187.4.16.112
4187.4.16.12/30187.4.16.13 to 187.4.16.14187.4.16.152
5187.4.16.16/30187.4.16.17 to 187.4.16.18187.4.16.192
6187.4.16.20/30187.4.16.21 to 187.4.16.22187.4.16.232
7187.4.16.24/30187.4.16.25 to 187.4.16.26187.4.16.272
8187.4.16.28/30187.4.16.29 to 187.4.16.30187.4.16.312
9187.4.16.32/30187.4.16.33 to 187.4.16.34187.4.16.352
10187.4.16.36/30187.4.16.37 to 187.4.16.38187.4.16.392
11187.4.16.40/30187.4.16.41 to 187.4.16.42187.4.16.432
12187.4.16.44/30187.4.16.45 to 187.4.16.46187.4.16.472
13187.4.16.48/30187.4.16.49 to 187.4.16.50187.4.16.512
14187.4.16.52/30187.4.16.53 to 187.4.16.54187.4.16.552
15187.4.16.56/30187.4.16.57 to 187.4.16.58187.4.16.592
16187.4.16.60/30187.4.16.61 to 187.4.16.62187.4.16.632
17187.4.16.64/30187.4.16.65 to 187.4.16.66187.4.16.672
18187.4.16.68/30187.4.16.69 to 187.4.16.70187.4.16.712
19187.4.16.72/30187.4.16.73 to 187.4.16.74187.4.16.752
20187.4.16.76/30187.4.16.77 to 187.4.16.78187.4.16.792
21187.4.16.80/30187.4.16.81 to 187.4.16.82187.4.16.832
22187.4.16.84/30187.4.16.85 to 187.4.16.86187.4.16.872
23187.4.16.88/30187.4.16.89 to 187.4.16.90187.4.16.912
24187.4.16.92/30187.4.16.93 to 187.4.16.94187.4.16.952
25187.4.16.96/30187.4.16.97 to 187.4.16.98187.4.16.992
26187.4.16.100/30187.4.16.101 to 187.4.16.102187.4.16.1032
27187.4.16.104/30187.4.16.105 to 187.4.16.106187.4.16.1072
28187.4.16.108/30187.4.16.109 to 187.4.16.110187.4.16.1112
29187.4.16.112/30187.4.16.113 to 187.4.16.114187.4.16.1152
30187.4.16.116/30187.4.16.117 to 187.4.16.118187.4.16.1192
31187.4.16.120/30187.4.16.121 to 187.4.16.122187.4.16.1232
32187.4.16.124/30187.4.16.125 to 187.4.16.126187.4.16.1272
33187.4.16.128/30187.4.16.129 to 187.4.16.130187.4.16.1312
34187.4.16.132/30187.4.16.133 to 187.4.16.134187.4.16.1352
35187.4.16.136/30187.4.16.137 to 187.4.16.138187.4.16.1392
36187.4.16.140/30187.4.16.141 to 187.4.16.142187.4.16.1432
37187.4.16.144/30187.4.16.145 to 187.4.16.146187.4.16.1472
38187.4.16.148/30187.4.16.149 to 187.4.16.150187.4.16.1512
39187.4.16.152/30187.4.16.153 to 187.4.16.154187.4.16.1552
40187.4.16.156/30187.4.16.157 to 187.4.16.158187.4.16.1592
41187.4.16.160/30187.4.16.161 to 187.4.16.162187.4.16.1632
42187.4.16.164/30187.4.16.165 to 187.4.16.166187.4.16.1672
43187.4.16.168/30187.4.16.169 to 187.4.16.170187.4.16.1712
44187.4.16.172/30187.4.16.173 to 187.4.16.174187.4.16.1752
45187.4.16.176/30187.4.16.177 to 187.4.16.178187.4.16.1792
46187.4.16.180/30187.4.16.181 to 187.4.16.182187.4.16.1832
47187.4.16.184/30187.4.16.185 to 187.4.16.186187.4.16.1872
48187.4.16.188/30187.4.16.189 to 187.4.16.190187.4.16.1912
49187.4.16.192/30187.4.16.193 to 187.4.16.194187.4.16.1952
50187.4.16.196/30187.4.16.197 to 187.4.16.198187.4.16.1992
51187.4.16.200/30187.4.16.201 to 187.4.16.202187.4.16.2032
52187.4.16.204/30187.4.16.205 to 187.4.16.206187.4.16.2072
53187.4.16.208/30187.4.16.209 to 187.4.16.210187.4.16.2112
54187.4.16.212/30187.4.16.213 to 187.4.16.214187.4.16.2152
55187.4.16.216/30187.4.16.217 to 187.4.16.218187.4.16.2192
56187.4.16.220/30187.4.16.221 to 187.4.16.222187.4.16.2232
57187.4.16.224/30187.4.16.225 to 187.4.16.226187.4.16.2272
58187.4.16.228/30187.4.16.229 to 187.4.16.230187.4.16.2312
59187.4.16.232/30187.4.16.233 to 187.4.16.234187.4.16.2352
60187.4.16.236/30187.4.16.237 to 187.4.16.238187.4.16.2392
61187.4.16.240/30187.4.16.241 to 187.4.16.242187.4.16.2432
62187.4.16.244/30187.4.16.245 to 187.4.16.246187.4.16.2472
63187.4.16.248/30187.4.16.249 to 187.4.16.250187.4.16.2512
64187.4.16.252/30187.4.16.253 to 187.4.16.254187.4.16.2552
65187.4.17.0/30187.4.17.1 to 187.4.17.2187.4.17.32
66187.4.17.4/30187.4.17.5 to 187.4.17.6187.4.17.72
67187.4.17.8/30187.4.17.9 to 187.4.17.10187.4.17.112
68187.4.17.12/30187.4.17.13 to 187.4.17.14187.4.17.152
69187.4.17.16/30187.4.17.17 to 187.4.17.18187.4.17.192
70187.4.17.20/30187.4.17.21 to 187.4.17.22187.4.17.232
71187.4.17.24/30187.4.17.25 to 187.4.17.26187.4.17.272
72187.4.17.28/30187.4.17.29 to 187.4.17.30187.4.17.312
73187.4.17.32/30187.4.17.33 to 187.4.17.34187.4.17.352
74187.4.17.36/30187.4.17.37 to 187.4.17.38187.4.17.392
75187.4.17.40/30187.4.17.41 to 187.4.17.42187.4.17.432
76187.4.17.44/30187.4.17.45 to 187.4.17.46187.4.17.472
77187.4.17.48/30187.4.17.49 to 187.4.17.50187.4.17.512
78187.4.17.52/30187.4.17.53 to 187.4.17.54187.4.17.552
79187.4.17.56/30187.4.17.57 to 187.4.17.58187.4.17.592
80187.4.17.60/30187.4.17.61 to 187.4.17.62187.4.17.632
81187.4.17.64/30187.4.17.65 to 187.4.17.66187.4.17.672
82187.4.17.68/30187.4.17.69 to 187.4.17.70187.4.17.712
83187.4.17.72/30187.4.17.73 to 187.4.17.74187.4.17.752
84187.4.17.76/30187.4.17.77 to 187.4.17.78187.4.17.792
85187.4.17.80/30187.4.17.81 to 187.4.17.82187.4.17.832
86187.4.17.84/30187.4.17.85 to 187.4.17.86187.4.17.872
87187.4.17.88/30187.4.17.89 to 187.4.17.90187.4.17.912
88187.4.17.92/30187.4.17.93 to 187.4.17.94187.4.17.952
89187.4.17.96/30187.4.17.97 to 187.4.17.98187.4.17.992
90187.4.17.100/30187.4.17.101 to 187.4.17.102187.4.17.1032
91187.4.17.104/30187.4.17.105 to 187.4.17.106187.4.17.1072
92187.4.17.108/30187.4.17.109 to 187.4.17.110187.4.17.1112
93187.4.17.112/30187.4.17.113 to 187.4.17.114187.4.17.1152
94187.4.17.116/30187.4.17.117 to 187.4.17.118187.4.17.1192
95187.4.17.120/30187.4.17.121 to 187.4.17.122187.4.17.1232
96187.4.17.124/30187.4.17.125 to 187.4.17.126187.4.17.1272
97187.4.17.128/30187.4.17.129 to 187.4.17.130187.4.17.1312
98187.4.17.132/30187.4.17.133 to 187.4.17.134187.4.17.1352
99187.4.17.136/30187.4.17.137 to 187.4.17.138187.4.17.1392
100187.4.17.140/30187.4.17.141 to 187.4.17.142187.4.17.1432
101187.4.17.144/30187.4.17.145 to 187.4.17.146187.4.17.1472
102187.4.17.148/30187.4.17.149 to 187.4.17.150187.4.17.1512
103187.4.17.152/30187.4.17.153 to 187.4.17.154187.4.17.1552
104187.4.17.156/30187.4.17.157 to 187.4.17.158187.4.17.1592
105187.4.17.160/30187.4.17.161 to 187.4.17.162187.4.17.1632
106187.4.17.164/30187.4.17.165 to 187.4.17.166187.4.17.1672
107187.4.17.168/30187.4.17.169 to 187.4.17.170187.4.17.1712
108187.4.17.172/30187.4.17.173 to 187.4.17.174187.4.17.1752
109187.4.17.176/30187.4.17.177 to 187.4.17.178187.4.17.1792
110187.4.17.180/30187.4.17.181 to 187.4.17.182187.4.17.1832
111187.4.17.184/30187.4.17.185 to 187.4.17.186187.4.17.1872
112187.4.17.188/30187.4.17.189 to 187.4.17.190187.4.17.1912
113187.4.17.192/30187.4.17.193 to 187.4.17.194187.4.17.1952
114187.4.17.196/30187.4.17.197 to 187.4.17.198187.4.17.1992
115187.4.17.200/30187.4.17.201 to 187.4.17.202187.4.17.2032
116187.4.17.204/30187.4.17.205 to 187.4.17.206187.4.17.2072
117187.4.17.208/30187.4.17.209 to 187.4.17.210187.4.17.2112
118187.4.17.212/30187.4.17.213 to 187.4.17.214187.4.17.2152
119187.4.17.216/30187.4.17.217 to 187.4.17.218187.4.17.2192
120187.4.17.220/30187.4.17.221 to 187.4.17.222187.4.17.2232
121187.4.17.224/30187.4.17.225 to 187.4.17.226187.4.17.2272
122187.4.17.228/30187.4.17.229 to 187.4.17.230187.4.17.2312
123187.4.17.232/30187.4.17.233 to 187.4.17.234187.4.17.2352
124187.4.17.236/30187.4.17.237 to 187.4.17.238187.4.17.2392
125187.4.17.240/30187.4.17.241 to 187.4.17.242187.4.17.2432
126187.4.17.244/30187.4.17.245 to 187.4.17.246187.4.17.2472
127187.4.17.248/30187.4.17.249 to 187.4.17.250187.4.17.2512
128187.4.17.252/30187.4.17.253 to 187.4.17.254187.4.17.2552
129187.4.18.0/30187.4.18.1 to 187.4.18.2187.4.18.32
130187.4.18.4/30187.4.18.5 to 187.4.18.6187.4.18.72
131187.4.18.8/30187.4.18.9 to 187.4.18.10187.4.18.112
132187.4.18.12/30187.4.18.13 to 187.4.18.14187.4.18.152
133187.4.18.16/30187.4.18.17 to 187.4.18.18187.4.18.192
134187.4.18.20/30187.4.18.21 to 187.4.18.22187.4.18.232
135187.4.18.24/30187.4.18.25 to 187.4.18.26187.4.18.272
136187.4.18.28/30187.4.18.29 to 187.4.18.30187.4.18.312
137187.4.18.32/30187.4.18.33 to 187.4.18.34187.4.18.352
138187.4.18.36/30187.4.18.37 to 187.4.18.38187.4.18.392
139187.4.18.40/30187.4.18.41 to 187.4.18.42187.4.18.432
140187.4.18.44/30187.4.18.45 to 187.4.18.46187.4.18.472
141187.4.18.48/30187.4.18.49 to 187.4.18.50187.4.18.512
142187.4.18.52/30187.4.18.53 to 187.4.18.54187.4.18.552
143187.4.18.56/30187.4.18.57 to 187.4.18.58187.4.18.592
144187.4.18.60/30187.4.18.61 to 187.4.18.62187.4.18.632
145187.4.18.64/30187.4.18.65 to 187.4.18.66187.4.18.672
146187.4.18.68/30187.4.18.69 to 187.4.18.70187.4.18.712
147187.4.18.72/30187.4.18.73 to 187.4.18.74187.4.18.752
148187.4.18.76/30187.4.18.77 to 187.4.18.78187.4.18.792
149187.4.18.80/30187.4.18.81 to 187.4.18.82187.4.18.832
150187.4.18.84/30187.4.18.85 to 187.4.18.86187.4.18.872
151187.4.18.88/30187.4.18.89 to 187.4.18.90187.4.18.912
152187.4.18.92/30187.4.18.93 to 187.4.18.94187.4.18.952
153187.4.18.96/30187.4.18.97 to 187.4.18.98187.4.18.992
154187.4.18.100/30187.4.18.101 to 187.4.18.102187.4.18.1032
155187.4.18.104/30187.4.18.105 to 187.4.18.106187.4.18.1072
156187.4.18.108/30187.4.18.109 to 187.4.18.110187.4.18.1112
157187.4.18.112/30187.4.18.113 to 187.4.18.114187.4.18.1152
158187.4.18.116/30187.4.18.117 to 187.4.18.118187.4.18.1192
159187.4.18.120/30187.4.18.121 to 187.4.18.122187.4.18.1232
160187.4.18.124/30187.4.18.125 to 187.4.18.126187.4.18.1272
161187.4.18.128/30187.4.18.129 to 187.4.18.130187.4.18.1312
162187.4.18.132/30187.4.18.133 to 187.4.18.134187.4.18.1352
163187.4.18.136/30187.4.18.137 to 187.4.18.138187.4.18.1392
164187.4.18.140/30187.4.18.141 to 187.4.18.142187.4.18.1432
165187.4.18.144/30187.4.18.145 to 187.4.18.146187.4.18.1472
166187.4.18.148/30187.4.18.149 to 187.4.18.150187.4.18.1512
167187.4.18.152/30187.4.18.153 to 187.4.18.154187.4.18.1552
168187.4.18.156/30187.4.18.157 to 187.4.18.158187.4.18.1592
169187.4.18.160/30187.4.18.161 to 187.4.18.162187.4.18.1632
170187.4.18.164/30187.4.18.165 to 187.4.18.166187.4.18.1672
171187.4.18.168/30187.4.18.169 to 187.4.18.170187.4.18.1712
172187.4.18.172/30187.4.18.173 to 187.4.18.174187.4.18.1752
173187.4.18.176/30187.4.18.177 to 187.4.18.178187.4.18.1792
174187.4.18.180/30187.4.18.181 to 187.4.18.182187.4.18.1832
175187.4.18.184/30187.4.18.185 to 187.4.18.186187.4.18.1872
176187.4.18.188/30187.4.18.189 to 187.4.18.190187.4.18.1912
177187.4.18.192/30187.4.18.193 to 187.4.18.194187.4.18.1952
178187.4.18.196/30187.4.18.197 to 187.4.18.198187.4.18.1992
179187.4.18.200/30187.4.18.201 to 187.4.18.202187.4.18.2032
180187.4.18.204/30187.4.18.205 to 187.4.18.206187.4.18.2072
181187.4.18.208/30187.4.18.209 to 187.4.18.210187.4.18.2112
182187.4.18.212/30187.4.18.213 to 187.4.18.214187.4.18.2152
183187.4.18.216/30187.4.18.217 to 187.4.18.218187.4.18.2192
184187.4.18.220/30187.4.18.221 to 187.4.18.222187.4.18.2232
185187.4.18.224/30187.4.18.225 to 187.4.18.226187.4.18.2272
186187.4.18.228/30187.4.18.229 to 187.4.18.230187.4.18.2312
187187.4.18.232/30187.4.18.233 to 187.4.18.234187.4.18.2352
188187.4.18.236/30187.4.18.237 to 187.4.18.238187.4.18.2392
189187.4.18.240/30187.4.18.241 to 187.4.18.242187.4.18.2432
190187.4.18.244/30187.4.18.245 to 187.4.18.246187.4.18.2472
191187.4.18.248/30187.4.18.249 to 187.4.18.250187.4.18.2512
192187.4.18.252/30187.4.18.253 to 187.4.18.254187.4.18.2552
193187.4.19.0/30187.4.19.1 to 187.4.19.2187.4.19.32
194187.4.19.4/30187.4.19.5 to 187.4.19.6187.4.19.72
195187.4.19.8/30187.4.19.9 to 187.4.19.10187.4.19.112
196187.4.19.12/30187.4.19.13 to 187.4.19.14187.4.19.152
197187.4.19.16/30187.4.19.17 to 187.4.19.18187.4.19.192
198187.4.19.20/30187.4.19.21 to 187.4.19.22187.4.19.232
199187.4.19.24/30187.4.19.25 to 187.4.19.26187.4.19.272
200187.4.19.28/30187.4.19.29 to 187.4.19.30187.4.19.312
201187.4.19.32/30187.4.19.33 to 187.4.19.34187.4.19.352
202187.4.19.36/30187.4.19.37 to 187.4.19.38187.4.19.392
203187.4.19.40/30187.4.19.41 to 187.4.19.42187.4.19.432
204187.4.19.44/30187.4.19.45 to 187.4.19.46187.4.19.472
205187.4.19.48/30187.4.19.49 to 187.4.19.50187.4.19.512
206187.4.19.52/30187.4.19.53 to 187.4.19.54187.4.19.552
207187.4.19.56/30187.4.19.57 to 187.4.19.58187.4.19.592
208187.4.19.60/30187.4.19.61 to 187.4.19.62187.4.19.632
209187.4.19.64/30187.4.19.65 to 187.4.19.66187.4.19.672
210187.4.19.68/30187.4.19.69 to 187.4.19.70187.4.19.712
211187.4.19.72/30187.4.19.73 to 187.4.19.74187.4.19.752
212187.4.19.76/30187.4.19.77 to 187.4.19.78187.4.19.792
213187.4.19.80/30187.4.19.81 to 187.4.19.82187.4.19.832
214187.4.19.84/30187.4.19.85 to 187.4.19.86187.4.19.872
215187.4.19.88/30187.4.19.89 to 187.4.19.90187.4.19.912
216187.4.19.92/30187.4.19.93 to 187.4.19.94187.4.19.952
217187.4.19.96/30187.4.19.97 to 187.4.19.98187.4.19.992
218187.4.19.100/30187.4.19.101 to 187.4.19.102187.4.19.1032
219187.4.19.104/30187.4.19.105 to 187.4.19.106187.4.19.1072
220187.4.19.108/30187.4.19.109 to 187.4.19.110187.4.19.1112
221187.4.19.112/30187.4.19.113 to 187.4.19.114187.4.19.1152
222187.4.19.116/30187.4.19.117 to 187.4.19.118187.4.19.1192
223187.4.19.120/30187.4.19.121 to 187.4.19.122187.4.19.1232
224187.4.19.124/30187.4.19.125 to 187.4.19.126187.4.19.1272
225187.4.19.128/30187.4.19.129 to 187.4.19.130187.4.19.1312
226187.4.19.132/30187.4.19.133 to 187.4.19.134187.4.19.1352
227187.4.19.136/30187.4.19.137 to 187.4.19.138187.4.19.1392
228187.4.19.140/30187.4.19.141 to 187.4.19.142187.4.19.1432
229187.4.19.144/30187.4.19.145 to 187.4.19.146187.4.19.1472
230187.4.19.148/30187.4.19.149 to 187.4.19.150187.4.19.1512
231187.4.19.152/30187.4.19.153 to 187.4.19.154187.4.19.1552
232187.4.19.156/30187.4.19.157 to 187.4.19.158187.4.19.1592
233187.4.19.160/30187.4.19.161 to 187.4.19.162187.4.19.1632
234187.4.19.164/30187.4.19.165 to 187.4.19.166187.4.19.1672
235187.4.19.168/30187.4.19.169 to 187.4.19.170187.4.19.1712
236187.4.19.172/30187.4.19.173 to 187.4.19.174187.4.19.1752
237187.4.19.176/30187.4.19.177 to 187.4.19.178187.4.19.1792
238187.4.19.180/30187.4.19.181 to 187.4.19.182187.4.19.1832
239187.4.19.184/30187.4.19.185 to 187.4.19.186187.4.19.1872
240187.4.19.188/30187.4.19.189 to 187.4.19.190187.4.19.1912
241187.4.19.192/30187.4.19.193 to 187.4.19.194187.4.19.1952
242187.4.19.196/30187.4.19.197 to 187.4.19.198187.4.19.1992
243187.4.19.200/30187.4.19.201 to 187.4.19.202187.4.19.2032
244187.4.19.204/30187.4.19.205 to 187.4.19.206187.4.19.2072
245187.4.19.208/30187.4.19.209 to 187.4.19.210187.4.19.2112
246187.4.19.212/30187.4.19.213 to 187.4.19.214187.4.19.2152
247187.4.19.216/30187.4.19.217 to 187.4.19.218187.4.19.2192
248187.4.19.220/30187.4.19.221 to 187.4.19.222187.4.19.2232
249187.4.19.224/30187.4.19.225 to 187.4.19.226187.4.19.2272
250187.4.19.228/30187.4.19.229 to 187.4.19.230187.4.19.2312
251187.4.19.232/30187.4.19.233 to 187.4.19.234187.4.19.2352
252187.4.19.236/30187.4.19.237 to 187.4.19.238187.4.19.2392
253187.4.19.240/30187.4.19.241 to 187.4.19.242187.4.19.2432
254187.4.19.244/30187.4.19.245 to 187.4.19.246187.4.19.2472
255187.4.19.248/30187.4.19.249 to 187.4.19.250187.4.19.2512
256187.4.19.252/30187.4.19.253 to 187.4.19.254187.4.19.2552

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.