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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.

Network251.64.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
251.64.0.0
Broadcast address
251.127.255.255
First usable
251.64.0.1
Last usable
251.127.255.254
Usable hosts
4,194,302 (4,194,304 less the network and broadcast addresses)
Subnet mask
255.192.0.0
Wildcard mask
0.63.255.255 (Cisco ACLs, OSPF)
Prefix length
/10
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex FB400000 · Integer 4215275520 to 4219469823
Reverse DNS zones
64.251.in-addr.arpa
65.251.in-addr.arpa
66.251.in-addr.arpa
67.251.in-addr.arpa
68.251.in-addr.arpa
69.251.in-addr.arpa
70.251.in-addr.arpa
71.251.in-addr.arpa
72.251.in-addr.arpa
73.251.in-addr.arpa
74.251.in-addr.arpa
75.251.in-addr.arpa
76.251.in-addr.arpa
77.251.in-addr.arpa
78.251.in-addr.arpa
79.251.in-addr.arpa
and 48 more
/10 is not on a 8-bit boundary, so it takes 64 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11111011.01000000.00000000.00000000251.64.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network11111011.01000000.00000000.00000000251.64.0.0
Broadcast11111011.01111111.11111111.11111111251.127.255.255
Split into smaller subnets/21
/11 (2)/12 (4)/13 (8)/14 (16)/15 (32)/16 (64)/17 (128)/18 (256)/19 (512)/20 (1,024)/21 (2,048)/22 (4,096)

251.64.0.0/10 makes 2,048 subnets of /21; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1251.64.0.0/21251.64.0.1 to 251.64.7.254251.64.7.2552,046
2251.64.8.0/21251.64.8.1 to 251.64.15.254251.64.15.2552,046
3251.64.16.0/21251.64.16.1 to 251.64.23.254251.64.23.2552,046
4251.64.24.0/21251.64.24.1 to 251.64.31.254251.64.31.2552,046
5251.64.32.0/21251.64.32.1 to 251.64.39.254251.64.39.2552,046
6251.64.40.0/21251.64.40.1 to 251.64.47.254251.64.47.2552,046
7251.64.48.0/21251.64.48.1 to 251.64.55.254251.64.55.2552,046
8251.64.56.0/21251.64.56.1 to 251.64.63.254251.64.63.2552,046
9251.64.64.0/21251.64.64.1 to 251.64.71.254251.64.71.2552,046
10251.64.72.0/21251.64.72.1 to 251.64.79.254251.64.79.2552,046
11251.64.80.0/21251.64.80.1 to 251.64.87.254251.64.87.2552,046
12251.64.88.0/21251.64.88.1 to 251.64.95.254251.64.95.2552,046
13251.64.96.0/21251.64.96.1 to 251.64.103.254251.64.103.2552,046
14251.64.104.0/21251.64.104.1 to 251.64.111.254251.64.111.2552,046
15251.64.112.0/21251.64.112.1 to 251.64.119.254251.64.119.2552,046
16251.64.120.0/21251.64.120.1 to 251.64.127.254251.64.127.2552,046
17251.64.128.0/21251.64.128.1 to 251.64.135.254251.64.135.2552,046
18251.64.136.0/21251.64.136.1 to 251.64.143.254251.64.143.2552,046
19251.64.144.0/21251.64.144.1 to 251.64.151.254251.64.151.2552,046
20251.64.152.0/21251.64.152.1 to 251.64.159.254251.64.159.2552,046
21251.64.160.0/21251.64.160.1 to 251.64.167.254251.64.167.2552,046
22251.64.168.0/21251.64.168.1 to 251.64.175.254251.64.175.2552,046
23251.64.176.0/21251.64.176.1 to 251.64.183.254251.64.183.2552,046
24251.64.184.0/21251.64.184.1 to 251.64.191.254251.64.191.2552,046
25251.64.192.0/21251.64.192.1 to 251.64.199.254251.64.199.2552,046
26251.64.200.0/21251.64.200.1 to 251.64.207.254251.64.207.2552,046
27251.64.208.0/21251.64.208.1 to 251.64.215.254251.64.215.2552,046
28251.64.216.0/21251.64.216.1 to 251.64.223.254251.64.223.2552,046
29251.64.224.0/21251.64.224.1 to 251.64.231.254251.64.231.2552,046
30251.64.232.0/21251.64.232.1 to 251.64.239.254251.64.239.2552,046
31251.64.240.0/21251.64.240.1 to 251.64.247.254251.64.247.2552,046
32251.64.248.0/21251.64.248.1 to 251.64.255.254251.64.255.2552,046
33251.65.0.0/21251.65.0.1 to 251.65.7.254251.65.7.2552,046
34251.65.8.0/21251.65.8.1 to 251.65.15.254251.65.15.2552,046
35251.65.16.0/21251.65.16.1 to 251.65.23.254251.65.23.2552,046
36251.65.24.0/21251.65.24.1 to 251.65.31.254251.65.31.2552,046
37251.65.32.0/21251.65.32.1 to 251.65.39.254251.65.39.2552,046
38251.65.40.0/21251.65.40.1 to 251.65.47.254251.65.47.2552,046
39251.65.48.0/21251.65.48.1 to 251.65.55.254251.65.55.2552,046
40251.65.56.0/21251.65.56.1 to 251.65.63.254251.65.63.2552,046
41251.65.64.0/21251.65.64.1 to 251.65.71.254251.65.71.2552,046
42251.65.72.0/21251.65.72.1 to 251.65.79.254251.65.79.2552,046
43251.65.80.0/21251.65.80.1 to 251.65.87.254251.65.87.2552,046
44251.65.88.0/21251.65.88.1 to 251.65.95.254251.65.95.2552,046
45251.65.96.0/21251.65.96.1 to 251.65.103.254251.65.103.2552,046
46251.65.104.0/21251.65.104.1 to 251.65.111.254251.65.111.2552,046
47251.65.112.0/21251.65.112.1 to 251.65.119.254251.65.119.2552,046
48251.65.120.0/21251.65.120.1 to 251.65.127.254251.65.127.2552,046
49251.65.128.0/21251.65.128.1 to 251.65.135.254251.65.135.2552,046
50251.65.136.0/21251.65.136.1 to 251.65.143.254251.65.143.2552,046
51251.65.144.0/21251.65.144.1 to 251.65.151.254251.65.151.2552,046
52251.65.152.0/21251.65.152.1 to 251.65.159.254251.65.159.2552,046
53251.65.160.0/21251.65.160.1 to 251.65.167.254251.65.167.2552,046
54251.65.168.0/21251.65.168.1 to 251.65.175.254251.65.175.2552,046
55251.65.176.0/21251.65.176.1 to 251.65.183.254251.65.183.2552,046
56251.65.184.0/21251.65.184.1 to 251.65.191.254251.65.191.2552,046
57251.65.192.0/21251.65.192.1 to 251.65.199.254251.65.199.2552,046
58251.65.200.0/21251.65.200.1 to 251.65.207.254251.65.207.2552,046
59251.65.208.0/21251.65.208.1 to 251.65.215.254251.65.215.2552,046
60251.65.216.0/21251.65.216.1 to 251.65.223.254251.65.223.2552,046
61251.65.224.0/21251.65.224.1 to 251.65.231.254251.65.231.2552,046
62251.65.232.0/21251.65.232.1 to 251.65.239.254251.65.239.2552,046
63251.65.240.0/21251.65.240.1 to 251.65.247.254251.65.247.2552,046
64251.65.248.0/21251.65.248.1 to 251.65.255.254251.65.255.2552,046
65251.66.0.0/21251.66.0.1 to 251.66.7.254251.66.7.2552,046
66251.66.8.0/21251.66.8.1 to 251.66.15.254251.66.15.2552,046
67251.66.16.0/21251.66.16.1 to 251.66.23.254251.66.23.2552,046
68251.66.24.0/21251.66.24.1 to 251.66.31.254251.66.31.2552,046
69251.66.32.0/21251.66.32.1 to 251.66.39.254251.66.39.2552,046
70251.66.40.0/21251.66.40.1 to 251.66.47.254251.66.47.2552,046
71251.66.48.0/21251.66.48.1 to 251.66.55.254251.66.55.2552,046
72251.66.56.0/21251.66.56.1 to 251.66.63.254251.66.63.2552,046
73251.66.64.0/21251.66.64.1 to 251.66.71.254251.66.71.2552,046
74251.66.72.0/21251.66.72.1 to 251.66.79.254251.66.79.2552,046
75251.66.80.0/21251.66.80.1 to 251.66.87.254251.66.87.2552,046
76251.66.88.0/21251.66.88.1 to 251.66.95.254251.66.95.2552,046
77251.66.96.0/21251.66.96.1 to 251.66.103.254251.66.103.2552,046
78251.66.104.0/21251.66.104.1 to 251.66.111.254251.66.111.2552,046
79251.66.112.0/21251.66.112.1 to 251.66.119.254251.66.119.2552,046
80251.66.120.0/21251.66.120.1 to 251.66.127.254251.66.127.2552,046
81251.66.128.0/21251.66.128.1 to 251.66.135.254251.66.135.2552,046
82251.66.136.0/21251.66.136.1 to 251.66.143.254251.66.143.2552,046
83251.66.144.0/21251.66.144.1 to 251.66.151.254251.66.151.2552,046
84251.66.152.0/21251.66.152.1 to 251.66.159.254251.66.159.2552,046
85251.66.160.0/21251.66.160.1 to 251.66.167.254251.66.167.2552,046
86251.66.168.0/21251.66.168.1 to 251.66.175.254251.66.175.2552,046
87251.66.176.0/21251.66.176.1 to 251.66.183.254251.66.183.2552,046
88251.66.184.0/21251.66.184.1 to 251.66.191.254251.66.191.2552,046
89251.66.192.0/21251.66.192.1 to 251.66.199.254251.66.199.2552,046
90251.66.200.0/21251.66.200.1 to 251.66.207.254251.66.207.2552,046
91251.66.208.0/21251.66.208.1 to 251.66.215.254251.66.215.2552,046
92251.66.216.0/21251.66.216.1 to 251.66.223.254251.66.223.2552,046
93251.66.224.0/21251.66.224.1 to 251.66.231.254251.66.231.2552,046
94251.66.232.0/21251.66.232.1 to 251.66.239.254251.66.239.2552,046
95251.66.240.0/21251.66.240.1 to 251.66.247.254251.66.247.2552,046
96251.66.248.0/21251.66.248.1 to 251.66.255.254251.66.255.2552,046
97251.67.0.0/21251.67.0.1 to 251.67.7.254251.67.7.2552,046
98251.67.8.0/21251.67.8.1 to 251.67.15.254251.67.15.2552,046
99251.67.16.0/21251.67.16.1 to 251.67.23.254251.67.23.2552,046
100251.67.24.0/21251.67.24.1 to 251.67.31.254251.67.31.2552,046
101251.67.32.0/21251.67.32.1 to 251.67.39.254251.67.39.2552,046
102251.67.40.0/21251.67.40.1 to 251.67.47.254251.67.47.2552,046
103251.67.48.0/21251.67.48.1 to 251.67.55.254251.67.55.2552,046
104251.67.56.0/21251.67.56.1 to 251.67.63.254251.67.63.2552,046
105251.67.64.0/21251.67.64.1 to 251.67.71.254251.67.71.2552,046
106251.67.72.0/21251.67.72.1 to 251.67.79.254251.67.79.2552,046
107251.67.80.0/21251.67.80.1 to 251.67.87.254251.67.87.2552,046
108251.67.88.0/21251.67.88.1 to 251.67.95.254251.67.95.2552,046
109251.67.96.0/21251.67.96.1 to 251.67.103.254251.67.103.2552,046
110251.67.104.0/21251.67.104.1 to 251.67.111.254251.67.111.2552,046
111251.67.112.0/21251.67.112.1 to 251.67.119.254251.67.119.2552,046
112251.67.120.0/21251.67.120.1 to 251.67.127.254251.67.127.2552,046
113251.67.128.0/21251.67.128.1 to 251.67.135.254251.67.135.2552,046
114251.67.136.0/21251.67.136.1 to 251.67.143.254251.67.143.2552,046
115251.67.144.0/21251.67.144.1 to 251.67.151.254251.67.151.2552,046
116251.67.152.0/21251.67.152.1 to 251.67.159.254251.67.159.2552,046
117251.67.160.0/21251.67.160.1 to 251.67.167.254251.67.167.2552,046
118251.67.168.0/21251.67.168.1 to 251.67.175.254251.67.175.2552,046
119251.67.176.0/21251.67.176.1 to 251.67.183.254251.67.183.2552,046
120251.67.184.0/21251.67.184.1 to 251.67.191.254251.67.191.2552,046
121251.67.192.0/21251.67.192.1 to 251.67.199.254251.67.199.2552,046
122251.67.200.0/21251.67.200.1 to 251.67.207.254251.67.207.2552,046
123251.67.208.0/21251.67.208.1 to 251.67.215.254251.67.215.2552,046
124251.67.216.0/21251.67.216.1 to 251.67.223.254251.67.223.2552,046
125251.67.224.0/21251.67.224.1 to 251.67.231.254251.67.231.2552,046
126251.67.232.0/21251.67.232.1 to 251.67.239.254251.67.239.2552,046
127251.67.240.0/21251.67.240.1 to 251.67.247.254251.67.247.2552,046
128251.67.248.0/21251.67.248.1 to 251.67.255.254251.67.255.2552,046
129251.68.0.0/21251.68.0.1 to 251.68.7.254251.68.7.2552,046
130251.68.8.0/21251.68.8.1 to 251.68.15.254251.68.15.2552,046
131251.68.16.0/21251.68.16.1 to 251.68.23.254251.68.23.2552,046
132251.68.24.0/21251.68.24.1 to 251.68.31.254251.68.31.2552,046
133251.68.32.0/21251.68.32.1 to 251.68.39.254251.68.39.2552,046
134251.68.40.0/21251.68.40.1 to 251.68.47.254251.68.47.2552,046
135251.68.48.0/21251.68.48.1 to 251.68.55.254251.68.55.2552,046
136251.68.56.0/21251.68.56.1 to 251.68.63.254251.68.63.2552,046
137251.68.64.0/21251.68.64.1 to 251.68.71.254251.68.71.2552,046
138251.68.72.0/21251.68.72.1 to 251.68.79.254251.68.79.2552,046
139251.68.80.0/21251.68.80.1 to 251.68.87.254251.68.87.2552,046
140251.68.88.0/21251.68.88.1 to 251.68.95.254251.68.95.2552,046
141251.68.96.0/21251.68.96.1 to 251.68.103.254251.68.103.2552,046
142251.68.104.0/21251.68.104.1 to 251.68.111.254251.68.111.2552,046
143251.68.112.0/21251.68.112.1 to 251.68.119.254251.68.119.2552,046
144251.68.120.0/21251.68.120.1 to 251.68.127.254251.68.127.2552,046
145251.68.128.0/21251.68.128.1 to 251.68.135.254251.68.135.2552,046
146251.68.136.0/21251.68.136.1 to 251.68.143.254251.68.143.2552,046
147251.68.144.0/21251.68.144.1 to 251.68.151.254251.68.151.2552,046
148251.68.152.0/21251.68.152.1 to 251.68.159.254251.68.159.2552,046
149251.68.160.0/21251.68.160.1 to 251.68.167.254251.68.167.2552,046
150251.68.168.0/21251.68.168.1 to 251.68.175.254251.68.175.2552,046
151251.68.176.0/21251.68.176.1 to 251.68.183.254251.68.183.2552,046
152251.68.184.0/21251.68.184.1 to 251.68.191.254251.68.191.2552,046
153251.68.192.0/21251.68.192.1 to 251.68.199.254251.68.199.2552,046
154251.68.200.0/21251.68.200.1 to 251.68.207.254251.68.207.2552,046
155251.68.208.0/21251.68.208.1 to 251.68.215.254251.68.215.2552,046
156251.68.216.0/21251.68.216.1 to 251.68.223.254251.68.223.2552,046
157251.68.224.0/21251.68.224.1 to 251.68.231.254251.68.231.2552,046
158251.68.232.0/21251.68.232.1 to 251.68.239.254251.68.239.2552,046
159251.68.240.0/21251.68.240.1 to 251.68.247.254251.68.247.2552,046
160251.68.248.0/21251.68.248.1 to 251.68.255.254251.68.255.2552,046
161251.69.0.0/21251.69.0.1 to 251.69.7.254251.69.7.2552,046
162251.69.8.0/21251.69.8.1 to 251.69.15.254251.69.15.2552,046
163251.69.16.0/21251.69.16.1 to 251.69.23.254251.69.23.2552,046
164251.69.24.0/21251.69.24.1 to 251.69.31.254251.69.31.2552,046
165251.69.32.0/21251.69.32.1 to 251.69.39.254251.69.39.2552,046
166251.69.40.0/21251.69.40.1 to 251.69.47.254251.69.47.2552,046
167251.69.48.0/21251.69.48.1 to 251.69.55.254251.69.55.2552,046
168251.69.56.0/21251.69.56.1 to 251.69.63.254251.69.63.2552,046
169251.69.64.0/21251.69.64.1 to 251.69.71.254251.69.71.2552,046
170251.69.72.0/21251.69.72.1 to 251.69.79.254251.69.79.2552,046
171251.69.80.0/21251.69.80.1 to 251.69.87.254251.69.87.2552,046
172251.69.88.0/21251.69.88.1 to 251.69.95.254251.69.95.2552,046
173251.69.96.0/21251.69.96.1 to 251.69.103.254251.69.103.2552,046
174251.69.104.0/21251.69.104.1 to 251.69.111.254251.69.111.2552,046
175251.69.112.0/21251.69.112.1 to 251.69.119.254251.69.119.2552,046
176251.69.120.0/21251.69.120.1 to 251.69.127.254251.69.127.2552,046
177251.69.128.0/21251.69.128.1 to 251.69.135.254251.69.135.2552,046
178251.69.136.0/21251.69.136.1 to 251.69.143.254251.69.143.2552,046
179251.69.144.0/21251.69.144.1 to 251.69.151.254251.69.151.2552,046
180251.69.152.0/21251.69.152.1 to 251.69.159.254251.69.159.2552,046
181251.69.160.0/21251.69.160.1 to 251.69.167.254251.69.167.2552,046
182251.69.168.0/21251.69.168.1 to 251.69.175.254251.69.175.2552,046
183251.69.176.0/21251.69.176.1 to 251.69.183.254251.69.183.2552,046
184251.69.184.0/21251.69.184.1 to 251.69.191.254251.69.191.2552,046
185251.69.192.0/21251.69.192.1 to 251.69.199.254251.69.199.2552,046
186251.69.200.0/21251.69.200.1 to 251.69.207.254251.69.207.2552,046
187251.69.208.0/21251.69.208.1 to 251.69.215.254251.69.215.2552,046
188251.69.216.0/21251.69.216.1 to 251.69.223.254251.69.223.2552,046
189251.69.224.0/21251.69.224.1 to 251.69.231.254251.69.231.2552,046
190251.69.232.0/21251.69.232.1 to 251.69.239.254251.69.239.2552,046
191251.69.240.0/21251.69.240.1 to 251.69.247.254251.69.247.2552,046
192251.69.248.0/21251.69.248.1 to 251.69.255.254251.69.255.2552,046
193251.70.0.0/21251.70.0.1 to 251.70.7.254251.70.7.2552,046
194251.70.8.0/21251.70.8.1 to 251.70.15.254251.70.15.2552,046
195251.70.16.0/21251.70.16.1 to 251.70.23.254251.70.23.2552,046
196251.70.24.0/21251.70.24.1 to 251.70.31.254251.70.31.2552,046
197251.70.32.0/21251.70.32.1 to 251.70.39.254251.70.39.2552,046
198251.70.40.0/21251.70.40.1 to 251.70.47.254251.70.47.2552,046
199251.70.48.0/21251.70.48.1 to 251.70.55.254251.70.55.2552,046
200251.70.56.0/21251.70.56.1 to 251.70.63.254251.70.63.2552,046
201251.70.64.0/21251.70.64.1 to 251.70.71.254251.70.71.2552,046
202251.70.72.0/21251.70.72.1 to 251.70.79.254251.70.79.2552,046
203251.70.80.0/21251.70.80.1 to 251.70.87.254251.70.87.2552,046
204251.70.88.0/21251.70.88.1 to 251.70.95.254251.70.95.2552,046
205251.70.96.0/21251.70.96.1 to 251.70.103.254251.70.103.2552,046
206251.70.104.0/21251.70.104.1 to 251.70.111.254251.70.111.2552,046
207251.70.112.0/21251.70.112.1 to 251.70.119.254251.70.119.2552,046
208251.70.120.0/21251.70.120.1 to 251.70.127.254251.70.127.2552,046
209251.70.128.0/21251.70.128.1 to 251.70.135.254251.70.135.2552,046
210251.70.136.0/21251.70.136.1 to 251.70.143.254251.70.143.2552,046
211251.70.144.0/21251.70.144.1 to 251.70.151.254251.70.151.2552,046
212251.70.152.0/21251.70.152.1 to 251.70.159.254251.70.159.2552,046
213251.70.160.0/21251.70.160.1 to 251.70.167.254251.70.167.2552,046
214251.70.168.0/21251.70.168.1 to 251.70.175.254251.70.175.2552,046
215251.70.176.0/21251.70.176.1 to 251.70.183.254251.70.183.2552,046
216251.70.184.0/21251.70.184.1 to 251.70.191.254251.70.191.2552,046
217251.70.192.0/21251.70.192.1 to 251.70.199.254251.70.199.2552,046
218251.70.200.0/21251.70.200.1 to 251.70.207.254251.70.207.2552,046
219251.70.208.0/21251.70.208.1 to 251.70.215.254251.70.215.2552,046
220251.70.216.0/21251.70.216.1 to 251.70.223.254251.70.223.2552,046
221251.70.224.0/21251.70.224.1 to 251.70.231.254251.70.231.2552,046
222251.70.232.0/21251.70.232.1 to 251.70.239.254251.70.239.2552,046
223251.70.240.0/21251.70.240.1 to 251.70.247.254251.70.247.2552,046
224251.70.248.0/21251.70.248.1 to 251.70.255.254251.70.255.2552,046
225251.71.0.0/21251.71.0.1 to 251.71.7.254251.71.7.2552,046
226251.71.8.0/21251.71.8.1 to 251.71.15.254251.71.15.2552,046
227251.71.16.0/21251.71.16.1 to 251.71.23.254251.71.23.2552,046
228251.71.24.0/21251.71.24.1 to 251.71.31.254251.71.31.2552,046
229251.71.32.0/21251.71.32.1 to 251.71.39.254251.71.39.2552,046
230251.71.40.0/21251.71.40.1 to 251.71.47.254251.71.47.2552,046
231251.71.48.0/21251.71.48.1 to 251.71.55.254251.71.55.2552,046
232251.71.56.0/21251.71.56.1 to 251.71.63.254251.71.63.2552,046
233251.71.64.0/21251.71.64.1 to 251.71.71.254251.71.71.2552,046
234251.71.72.0/21251.71.72.1 to 251.71.79.254251.71.79.2552,046
235251.71.80.0/21251.71.80.1 to 251.71.87.254251.71.87.2552,046
236251.71.88.0/21251.71.88.1 to 251.71.95.254251.71.95.2552,046
237251.71.96.0/21251.71.96.1 to 251.71.103.254251.71.103.2552,046
238251.71.104.0/21251.71.104.1 to 251.71.111.254251.71.111.2552,046
239251.71.112.0/21251.71.112.1 to 251.71.119.254251.71.119.2552,046
240251.71.120.0/21251.71.120.1 to 251.71.127.254251.71.127.2552,046
241251.71.128.0/21251.71.128.1 to 251.71.135.254251.71.135.2552,046
242251.71.136.0/21251.71.136.1 to 251.71.143.254251.71.143.2552,046
243251.71.144.0/21251.71.144.1 to 251.71.151.254251.71.151.2552,046
244251.71.152.0/21251.71.152.1 to 251.71.159.254251.71.159.2552,046
245251.71.160.0/21251.71.160.1 to 251.71.167.254251.71.167.2552,046
246251.71.168.0/21251.71.168.1 to 251.71.175.254251.71.175.2552,046
247251.71.176.0/21251.71.176.1 to 251.71.183.254251.71.183.2552,046
248251.71.184.0/21251.71.184.1 to 251.71.191.254251.71.191.2552,046
249251.71.192.0/21251.71.192.1 to 251.71.199.254251.71.199.2552,046
250251.71.200.0/21251.71.200.1 to 251.71.207.254251.71.207.2552,046
251251.71.208.0/21251.71.208.1 to 251.71.215.254251.71.215.2552,046
252251.71.216.0/21251.71.216.1 to 251.71.223.254251.71.223.2552,046
253251.71.224.0/21251.71.224.1 to 251.71.231.254251.71.231.2552,046
254251.71.232.0/21251.71.232.1 to 251.71.239.254251.71.239.2552,046
255251.71.240.0/21251.71.240.1 to 251.71.247.254251.71.247.2552,046
256251.71.248.0/21251.71.248.1 to 251.71.255.254251.71.255.2552,046

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.