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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.

Network137.32.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
137.32.0.0
Broadcast address
137.47.255.255
First usable
137.32.0.1
Last usable
137.47.255.254
Usable hosts
1,048,574 (1,048,576 less the network and broadcast addresses)
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255 (Cisco ACLs, OSPF)
Prefix length
/12
Type
Public public
Old class
B (default /16)
As numbers
Hex 89200000 · Integer 2300575744 to 2301624319
Reverse DNS zones
32.137.in-addr.arpa
33.137.in-addr.arpa
34.137.in-addr.arpa
35.137.in-addr.arpa
36.137.in-addr.arpa
37.137.in-addr.arpa
38.137.in-addr.arpa
39.137.in-addr.arpa
40.137.in-addr.arpa
41.137.in-addr.arpa
42.137.in-addr.arpa
43.137.in-addr.arpa
44.137.in-addr.arpa
45.137.in-addr.arpa
46.137.in-addr.arpa
47.137.in-addr.arpa
/12 is not on a 8-bit boundary, so it takes 16 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10001001.00100000.00000000.00000000137.32.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network10001001.00100000.00000000.00000000137.32.0.0
Broadcast10001001.00101111.11111111.11111111137.47.255.255
Split into smaller subnets/21
/13 (2)/14 (4)/15 (8)/16 (16)/17 (32)/18 (64)/19 (128)/20 (256)/21 (512)/22 (1,024)/23 (2,048)/24 (4,096)

137.32.0.0/12 makes 512 subnets of /21; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1137.32.0.0/21137.32.0.1 to 137.32.7.254137.32.7.2552,046
2137.32.8.0/21137.32.8.1 to 137.32.15.254137.32.15.2552,046
3137.32.16.0/21137.32.16.1 to 137.32.23.254137.32.23.2552,046
4137.32.24.0/21137.32.24.1 to 137.32.31.254137.32.31.2552,046
5137.32.32.0/21137.32.32.1 to 137.32.39.254137.32.39.2552,046
6137.32.40.0/21137.32.40.1 to 137.32.47.254137.32.47.2552,046
7137.32.48.0/21137.32.48.1 to 137.32.55.254137.32.55.2552,046
8137.32.56.0/21137.32.56.1 to 137.32.63.254137.32.63.2552,046
9137.32.64.0/21137.32.64.1 to 137.32.71.254137.32.71.2552,046
10137.32.72.0/21137.32.72.1 to 137.32.79.254137.32.79.2552,046
11137.32.80.0/21137.32.80.1 to 137.32.87.254137.32.87.2552,046
12137.32.88.0/21137.32.88.1 to 137.32.95.254137.32.95.2552,046
13137.32.96.0/21137.32.96.1 to 137.32.103.254137.32.103.2552,046
14137.32.104.0/21137.32.104.1 to 137.32.111.254137.32.111.2552,046
15137.32.112.0/21137.32.112.1 to 137.32.119.254137.32.119.2552,046
16137.32.120.0/21137.32.120.1 to 137.32.127.254137.32.127.2552,046
17137.32.128.0/21137.32.128.1 to 137.32.135.254137.32.135.2552,046
18137.32.136.0/21137.32.136.1 to 137.32.143.254137.32.143.2552,046
19137.32.144.0/21137.32.144.1 to 137.32.151.254137.32.151.2552,046
20137.32.152.0/21137.32.152.1 to 137.32.159.254137.32.159.2552,046
21137.32.160.0/21137.32.160.1 to 137.32.167.254137.32.167.2552,046
22137.32.168.0/21137.32.168.1 to 137.32.175.254137.32.175.2552,046
23137.32.176.0/21137.32.176.1 to 137.32.183.254137.32.183.2552,046
24137.32.184.0/21137.32.184.1 to 137.32.191.254137.32.191.2552,046
25137.32.192.0/21137.32.192.1 to 137.32.199.254137.32.199.2552,046
26137.32.200.0/21137.32.200.1 to 137.32.207.254137.32.207.2552,046
27137.32.208.0/21137.32.208.1 to 137.32.215.254137.32.215.2552,046
28137.32.216.0/21137.32.216.1 to 137.32.223.254137.32.223.2552,046
29137.32.224.0/21137.32.224.1 to 137.32.231.254137.32.231.2552,046
30137.32.232.0/21137.32.232.1 to 137.32.239.254137.32.239.2552,046
31137.32.240.0/21137.32.240.1 to 137.32.247.254137.32.247.2552,046
32137.32.248.0/21137.32.248.1 to 137.32.255.254137.32.255.2552,046
33137.33.0.0/21137.33.0.1 to 137.33.7.254137.33.7.2552,046
34137.33.8.0/21137.33.8.1 to 137.33.15.254137.33.15.2552,046
35137.33.16.0/21137.33.16.1 to 137.33.23.254137.33.23.2552,046
36137.33.24.0/21137.33.24.1 to 137.33.31.254137.33.31.2552,046
37137.33.32.0/21137.33.32.1 to 137.33.39.254137.33.39.2552,046
38137.33.40.0/21137.33.40.1 to 137.33.47.254137.33.47.2552,046
39137.33.48.0/21137.33.48.1 to 137.33.55.254137.33.55.2552,046
40137.33.56.0/21137.33.56.1 to 137.33.63.254137.33.63.2552,046
41137.33.64.0/21137.33.64.1 to 137.33.71.254137.33.71.2552,046
42137.33.72.0/21137.33.72.1 to 137.33.79.254137.33.79.2552,046
43137.33.80.0/21137.33.80.1 to 137.33.87.254137.33.87.2552,046
44137.33.88.0/21137.33.88.1 to 137.33.95.254137.33.95.2552,046
45137.33.96.0/21137.33.96.1 to 137.33.103.254137.33.103.2552,046
46137.33.104.0/21137.33.104.1 to 137.33.111.254137.33.111.2552,046
47137.33.112.0/21137.33.112.1 to 137.33.119.254137.33.119.2552,046
48137.33.120.0/21137.33.120.1 to 137.33.127.254137.33.127.2552,046
49137.33.128.0/21137.33.128.1 to 137.33.135.254137.33.135.2552,046
50137.33.136.0/21137.33.136.1 to 137.33.143.254137.33.143.2552,046
51137.33.144.0/21137.33.144.1 to 137.33.151.254137.33.151.2552,046
52137.33.152.0/21137.33.152.1 to 137.33.159.254137.33.159.2552,046
53137.33.160.0/21137.33.160.1 to 137.33.167.254137.33.167.2552,046
54137.33.168.0/21137.33.168.1 to 137.33.175.254137.33.175.2552,046
55137.33.176.0/21137.33.176.1 to 137.33.183.254137.33.183.2552,046
56137.33.184.0/21137.33.184.1 to 137.33.191.254137.33.191.2552,046
57137.33.192.0/21137.33.192.1 to 137.33.199.254137.33.199.2552,046
58137.33.200.0/21137.33.200.1 to 137.33.207.254137.33.207.2552,046
59137.33.208.0/21137.33.208.1 to 137.33.215.254137.33.215.2552,046
60137.33.216.0/21137.33.216.1 to 137.33.223.254137.33.223.2552,046
61137.33.224.0/21137.33.224.1 to 137.33.231.254137.33.231.2552,046
62137.33.232.0/21137.33.232.1 to 137.33.239.254137.33.239.2552,046
63137.33.240.0/21137.33.240.1 to 137.33.247.254137.33.247.2552,046
64137.33.248.0/21137.33.248.1 to 137.33.255.254137.33.255.2552,046
65137.34.0.0/21137.34.0.1 to 137.34.7.254137.34.7.2552,046
66137.34.8.0/21137.34.8.1 to 137.34.15.254137.34.15.2552,046
67137.34.16.0/21137.34.16.1 to 137.34.23.254137.34.23.2552,046
68137.34.24.0/21137.34.24.1 to 137.34.31.254137.34.31.2552,046
69137.34.32.0/21137.34.32.1 to 137.34.39.254137.34.39.2552,046
70137.34.40.0/21137.34.40.1 to 137.34.47.254137.34.47.2552,046
71137.34.48.0/21137.34.48.1 to 137.34.55.254137.34.55.2552,046
72137.34.56.0/21137.34.56.1 to 137.34.63.254137.34.63.2552,046
73137.34.64.0/21137.34.64.1 to 137.34.71.254137.34.71.2552,046
74137.34.72.0/21137.34.72.1 to 137.34.79.254137.34.79.2552,046
75137.34.80.0/21137.34.80.1 to 137.34.87.254137.34.87.2552,046
76137.34.88.0/21137.34.88.1 to 137.34.95.254137.34.95.2552,046
77137.34.96.0/21137.34.96.1 to 137.34.103.254137.34.103.2552,046
78137.34.104.0/21137.34.104.1 to 137.34.111.254137.34.111.2552,046
79137.34.112.0/21137.34.112.1 to 137.34.119.254137.34.119.2552,046
80137.34.120.0/21137.34.120.1 to 137.34.127.254137.34.127.2552,046
81137.34.128.0/21137.34.128.1 to 137.34.135.254137.34.135.2552,046
82137.34.136.0/21137.34.136.1 to 137.34.143.254137.34.143.2552,046
83137.34.144.0/21137.34.144.1 to 137.34.151.254137.34.151.2552,046
84137.34.152.0/21137.34.152.1 to 137.34.159.254137.34.159.2552,046
85137.34.160.0/21137.34.160.1 to 137.34.167.254137.34.167.2552,046
86137.34.168.0/21137.34.168.1 to 137.34.175.254137.34.175.2552,046
87137.34.176.0/21137.34.176.1 to 137.34.183.254137.34.183.2552,046
88137.34.184.0/21137.34.184.1 to 137.34.191.254137.34.191.2552,046
89137.34.192.0/21137.34.192.1 to 137.34.199.254137.34.199.2552,046
90137.34.200.0/21137.34.200.1 to 137.34.207.254137.34.207.2552,046
91137.34.208.0/21137.34.208.1 to 137.34.215.254137.34.215.2552,046
92137.34.216.0/21137.34.216.1 to 137.34.223.254137.34.223.2552,046
93137.34.224.0/21137.34.224.1 to 137.34.231.254137.34.231.2552,046
94137.34.232.0/21137.34.232.1 to 137.34.239.254137.34.239.2552,046
95137.34.240.0/21137.34.240.1 to 137.34.247.254137.34.247.2552,046
96137.34.248.0/21137.34.248.1 to 137.34.255.254137.34.255.2552,046
97137.35.0.0/21137.35.0.1 to 137.35.7.254137.35.7.2552,046
98137.35.8.0/21137.35.8.1 to 137.35.15.254137.35.15.2552,046
99137.35.16.0/21137.35.16.1 to 137.35.23.254137.35.23.2552,046
100137.35.24.0/21137.35.24.1 to 137.35.31.254137.35.31.2552,046
101137.35.32.0/21137.35.32.1 to 137.35.39.254137.35.39.2552,046
102137.35.40.0/21137.35.40.1 to 137.35.47.254137.35.47.2552,046
103137.35.48.0/21137.35.48.1 to 137.35.55.254137.35.55.2552,046
104137.35.56.0/21137.35.56.1 to 137.35.63.254137.35.63.2552,046
105137.35.64.0/21137.35.64.1 to 137.35.71.254137.35.71.2552,046
106137.35.72.0/21137.35.72.1 to 137.35.79.254137.35.79.2552,046
107137.35.80.0/21137.35.80.1 to 137.35.87.254137.35.87.2552,046
108137.35.88.0/21137.35.88.1 to 137.35.95.254137.35.95.2552,046
109137.35.96.0/21137.35.96.1 to 137.35.103.254137.35.103.2552,046
110137.35.104.0/21137.35.104.1 to 137.35.111.254137.35.111.2552,046
111137.35.112.0/21137.35.112.1 to 137.35.119.254137.35.119.2552,046
112137.35.120.0/21137.35.120.1 to 137.35.127.254137.35.127.2552,046
113137.35.128.0/21137.35.128.1 to 137.35.135.254137.35.135.2552,046
114137.35.136.0/21137.35.136.1 to 137.35.143.254137.35.143.2552,046
115137.35.144.0/21137.35.144.1 to 137.35.151.254137.35.151.2552,046
116137.35.152.0/21137.35.152.1 to 137.35.159.254137.35.159.2552,046
117137.35.160.0/21137.35.160.1 to 137.35.167.254137.35.167.2552,046
118137.35.168.0/21137.35.168.1 to 137.35.175.254137.35.175.2552,046
119137.35.176.0/21137.35.176.1 to 137.35.183.254137.35.183.2552,046
120137.35.184.0/21137.35.184.1 to 137.35.191.254137.35.191.2552,046
121137.35.192.0/21137.35.192.1 to 137.35.199.254137.35.199.2552,046
122137.35.200.0/21137.35.200.1 to 137.35.207.254137.35.207.2552,046
123137.35.208.0/21137.35.208.1 to 137.35.215.254137.35.215.2552,046
124137.35.216.0/21137.35.216.1 to 137.35.223.254137.35.223.2552,046
125137.35.224.0/21137.35.224.1 to 137.35.231.254137.35.231.2552,046
126137.35.232.0/21137.35.232.1 to 137.35.239.254137.35.239.2552,046
127137.35.240.0/21137.35.240.1 to 137.35.247.254137.35.247.2552,046
128137.35.248.0/21137.35.248.1 to 137.35.255.254137.35.255.2552,046
129137.36.0.0/21137.36.0.1 to 137.36.7.254137.36.7.2552,046
130137.36.8.0/21137.36.8.1 to 137.36.15.254137.36.15.2552,046
131137.36.16.0/21137.36.16.1 to 137.36.23.254137.36.23.2552,046
132137.36.24.0/21137.36.24.1 to 137.36.31.254137.36.31.2552,046
133137.36.32.0/21137.36.32.1 to 137.36.39.254137.36.39.2552,046
134137.36.40.0/21137.36.40.1 to 137.36.47.254137.36.47.2552,046
135137.36.48.0/21137.36.48.1 to 137.36.55.254137.36.55.2552,046
136137.36.56.0/21137.36.56.1 to 137.36.63.254137.36.63.2552,046
137137.36.64.0/21137.36.64.1 to 137.36.71.254137.36.71.2552,046
138137.36.72.0/21137.36.72.1 to 137.36.79.254137.36.79.2552,046
139137.36.80.0/21137.36.80.1 to 137.36.87.254137.36.87.2552,046
140137.36.88.0/21137.36.88.1 to 137.36.95.254137.36.95.2552,046
141137.36.96.0/21137.36.96.1 to 137.36.103.254137.36.103.2552,046
142137.36.104.0/21137.36.104.1 to 137.36.111.254137.36.111.2552,046
143137.36.112.0/21137.36.112.1 to 137.36.119.254137.36.119.2552,046
144137.36.120.0/21137.36.120.1 to 137.36.127.254137.36.127.2552,046
145137.36.128.0/21137.36.128.1 to 137.36.135.254137.36.135.2552,046
146137.36.136.0/21137.36.136.1 to 137.36.143.254137.36.143.2552,046
147137.36.144.0/21137.36.144.1 to 137.36.151.254137.36.151.2552,046
148137.36.152.0/21137.36.152.1 to 137.36.159.254137.36.159.2552,046
149137.36.160.0/21137.36.160.1 to 137.36.167.254137.36.167.2552,046
150137.36.168.0/21137.36.168.1 to 137.36.175.254137.36.175.2552,046
151137.36.176.0/21137.36.176.1 to 137.36.183.254137.36.183.2552,046
152137.36.184.0/21137.36.184.1 to 137.36.191.254137.36.191.2552,046
153137.36.192.0/21137.36.192.1 to 137.36.199.254137.36.199.2552,046
154137.36.200.0/21137.36.200.1 to 137.36.207.254137.36.207.2552,046
155137.36.208.0/21137.36.208.1 to 137.36.215.254137.36.215.2552,046
156137.36.216.0/21137.36.216.1 to 137.36.223.254137.36.223.2552,046
157137.36.224.0/21137.36.224.1 to 137.36.231.254137.36.231.2552,046
158137.36.232.0/21137.36.232.1 to 137.36.239.254137.36.239.2552,046
159137.36.240.0/21137.36.240.1 to 137.36.247.254137.36.247.2552,046
160137.36.248.0/21137.36.248.1 to 137.36.255.254137.36.255.2552,046
161137.37.0.0/21137.37.0.1 to 137.37.7.254137.37.7.2552,046
162137.37.8.0/21137.37.8.1 to 137.37.15.254137.37.15.2552,046
163137.37.16.0/21137.37.16.1 to 137.37.23.254137.37.23.2552,046
164137.37.24.0/21137.37.24.1 to 137.37.31.254137.37.31.2552,046
165137.37.32.0/21137.37.32.1 to 137.37.39.254137.37.39.2552,046
166137.37.40.0/21137.37.40.1 to 137.37.47.254137.37.47.2552,046
167137.37.48.0/21137.37.48.1 to 137.37.55.254137.37.55.2552,046
168137.37.56.0/21137.37.56.1 to 137.37.63.254137.37.63.2552,046
169137.37.64.0/21137.37.64.1 to 137.37.71.254137.37.71.2552,046
170137.37.72.0/21137.37.72.1 to 137.37.79.254137.37.79.2552,046
171137.37.80.0/21137.37.80.1 to 137.37.87.254137.37.87.2552,046
172137.37.88.0/21137.37.88.1 to 137.37.95.254137.37.95.2552,046
173137.37.96.0/21137.37.96.1 to 137.37.103.254137.37.103.2552,046
174137.37.104.0/21137.37.104.1 to 137.37.111.254137.37.111.2552,046
175137.37.112.0/21137.37.112.1 to 137.37.119.254137.37.119.2552,046
176137.37.120.0/21137.37.120.1 to 137.37.127.254137.37.127.2552,046
177137.37.128.0/21137.37.128.1 to 137.37.135.254137.37.135.2552,046
178137.37.136.0/21137.37.136.1 to 137.37.143.254137.37.143.2552,046
179137.37.144.0/21137.37.144.1 to 137.37.151.254137.37.151.2552,046
180137.37.152.0/21137.37.152.1 to 137.37.159.254137.37.159.2552,046
181137.37.160.0/21137.37.160.1 to 137.37.167.254137.37.167.2552,046
182137.37.168.0/21137.37.168.1 to 137.37.175.254137.37.175.2552,046
183137.37.176.0/21137.37.176.1 to 137.37.183.254137.37.183.2552,046
184137.37.184.0/21137.37.184.1 to 137.37.191.254137.37.191.2552,046
185137.37.192.0/21137.37.192.1 to 137.37.199.254137.37.199.2552,046
186137.37.200.0/21137.37.200.1 to 137.37.207.254137.37.207.2552,046
187137.37.208.0/21137.37.208.1 to 137.37.215.254137.37.215.2552,046
188137.37.216.0/21137.37.216.1 to 137.37.223.254137.37.223.2552,046
189137.37.224.0/21137.37.224.1 to 137.37.231.254137.37.231.2552,046
190137.37.232.0/21137.37.232.1 to 137.37.239.254137.37.239.2552,046
191137.37.240.0/21137.37.240.1 to 137.37.247.254137.37.247.2552,046
192137.37.248.0/21137.37.248.1 to 137.37.255.254137.37.255.2552,046
193137.38.0.0/21137.38.0.1 to 137.38.7.254137.38.7.2552,046
194137.38.8.0/21137.38.8.1 to 137.38.15.254137.38.15.2552,046
195137.38.16.0/21137.38.16.1 to 137.38.23.254137.38.23.2552,046
196137.38.24.0/21137.38.24.1 to 137.38.31.254137.38.31.2552,046
197137.38.32.0/21137.38.32.1 to 137.38.39.254137.38.39.2552,046
198137.38.40.0/21137.38.40.1 to 137.38.47.254137.38.47.2552,046
199137.38.48.0/21137.38.48.1 to 137.38.55.254137.38.55.2552,046
200137.38.56.0/21137.38.56.1 to 137.38.63.254137.38.63.2552,046
201137.38.64.0/21137.38.64.1 to 137.38.71.254137.38.71.2552,046
202137.38.72.0/21137.38.72.1 to 137.38.79.254137.38.79.2552,046
203137.38.80.0/21137.38.80.1 to 137.38.87.254137.38.87.2552,046
204137.38.88.0/21137.38.88.1 to 137.38.95.254137.38.95.2552,046
205137.38.96.0/21137.38.96.1 to 137.38.103.254137.38.103.2552,046
206137.38.104.0/21137.38.104.1 to 137.38.111.254137.38.111.2552,046
207137.38.112.0/21137.38.112.1 to 137.38.119.254137.38.119.2552,046
208137.38.120.0/21137.38.120.1 to 137.38.127.254137.38.127.2552,046
209137.38.128.0/21137.38.128.1 to 137.38.135.254137.38.135.2552,046
210137.38.136.0/21137.38.136.1 to 137.38.143.254137.38.143.2552,046
211137.38.144.0/21137.38.144.1 to 137.38.151.254137.38.151.2552,046
212137.38.152.0/21137.38.152.1 to 137.38.159.254137.38.159.2552,046
213137.38.160.0/21137.38.160.1 to 137.38.167.254137.38.167.2552,046
214137.38.168.0/21137.38.168.1 to 137.38.175.254137.38.175.2552,046
215137.38.176.0/21137.38.176.1 to 137.38.183.254137.38.183.2552,046
216137.38.184.0/21137.38.184.1 to 137.38.191.254137.38.191.2552,046
217137.38.192.0/21137.38.192.1 to 137.38.199.254137.38.199.2552,046
218137.38.200.0/21137.38.200.1 to 137.38.207.254137.38.207.2552,046
219137.38.208.0/21137.38.208.1 to 137.38.215.254137.38.215.2552,046
220137.38.216.0/21137.38.216.1 to 137.38.223.254137.38.223.2552,046
221137.38.224.0/21137.38.224.1 to 137.38.231.254137.38.231.2552,046
222137.38.232.0/21137.38.232.1 to 137.38.239.254137.38.239.2552,046
223137.38.240.0/21137.38.240.1 to 137.38.247.254137.38.247.2552,046
224137.38.248.0/21137.38.248.1 to 137.38.255.254137.38.255.2552,046
225137.39.0.0/21137.39.0.1 to 137.39.7.254137.39.7.2552,046
226137.39.8.0/21137.39.8.1 to 137.39.15.254137.39.15.2552,046
227137.39.16.0/21137.39.16.1 to 137.39.23.254137.39.23.2552,046
228137.39.24.0/21137.39.24.1 to 137.39.31.254137.39.31.2552,046
229137.39.32.0/21137.39.32.1 to 137.39.39.254137.39.39.2552,046
230137.39.40.0/21137.39.40.1 to 137.39.47.254137.39.47.2552,046
231137.39.48.0/21137.39.48.1 to 137.39.55.254137.39.55.2552,046
232137.39.56.0/21137.39.56.1 to 137.39.63.254137.39.63.2552,046
233137.39.64.0/21137.39.64.1 to 137.39.71.254137.39.71.2552,046
234137.39.72.0/21137.39.72.1 to 137.39.79.254137.39.79.2552,046
235137.39.80.0/21137.39.80.1 to 137.39.87.254137.39.87.2552,046
236137.39.88.0/21137.39.88.1 to 137.39.95.254137.39.95.2552,046
237137.39.96.0/21137.39.96.1 to 137.39.103.254137.39.103.2552,046
238137.39.104.0/21137.39.104.1 to 137.39.111.254137.39.111.2552,046
239137.39.112.0/21137.39.112.1 to 137.39.119.254137.39.119.2552,046
240137.39.120.0/21137.39.120.1 to 137.39.127.254137.39.127.2552,046
241137.39.128.0/21137.39.128.1 to 137.39.135.254137.39.135.2552,046
242137.39.136.0/21137.39.136.1 to 137.39.143.254137.39.143.2552,046
243137.39.144.0/21137.39.144.1 to 137.39.151.254137.39.151.2552,046
244137.39.152.0/21137.39.152.1 to 137.39.159.254137.39.159.2552,046
245137.39.160.0/21137.39.160.1 to 137.39.167.254137.39.167.2552,046
246137.39.168.0/21137.39.168.1 to 137.39.175.254137.39.175.2552,046
247137.39.176.0/21137.39.176.1 to 137.39.183.254137.39.183.2552,046
248137.39.184.0/21137.39.184.1 to 137.39.191.254137.39.191.2552,046
249137.39.192.0/21137.39.192.1 to 137.39.199.254137.39.199.2552,046
250137.39.200.0/21137.39.200.1 to 137.39.207.254137.39.207.2552,046
251137.39.208.0/21137.39.208.1 to 137.39.215.254137.39.215.2552,046
252137.39.216.0/21137.39.216.1 to 137.39.223.254137.39.223.2552,046
253137.39.224.0/21137.39.224.1 to 137.39.231.254137.39.231.2552,046
254137.39.232.0/21137.39.232.1 to 137.39.239.254137.39.239.2552,046
255137.39.240.0/21137.39.240.1 to 137.39.247.254137.39.247.2552,046
256137.39.248.0/21137.39.248.1 to 137.39.255.254137.39.255.2552,046

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.