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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.

Network172.16.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
172.16.0.0
Broadcast address
172.31.255.255
First usable
172.16.0.1
Last usable
172.31.255.254
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
Private (RFC 1918) 172.16.0.0/12
Office and home networks; not routed on the internet
Old class
B (default /16)
As numbers
Hex AC100000 · Integer 2886729728 to 2887778303
Reverse DNS zones
16.172.in-addr.arpa
17.172.in-addr.arpa
18.172.in-addr.arpa
19.172.in-addr.arpa
20.172.in-addr.arpa
21.172.in-addr.arpa
22.172.in-addr.arpa
23.172.in-addr.arpa
24.172.in-addr.arpa
25.172.in-addr.arpa
26.172.in-addr.arpa
27.172.in-addr.arpa
28.172.in-addr.arpa
29.172.in-addr.arpa
30.172.in-addr.arpa
31.172.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
Address10101100.00010000.00000000.00000000172.16.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network10101100.00010000.00000000.00000000172.16.0.0
Broadcast10101100.00011111.11111111.11111111172.31.255.255
Split into smaller subnets/20
/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)

172.16.0.0/12 makes 256 subnets of /20.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1172.16.0.0/20172.16.0.1 to 172.16.15.254172.16.15.2554,094
2172.16.16.0/20172.16.16.1 to 172.16.31.254172.16.31.2554,094
3172.16.32.0/20172.16.32.1 to 172.16.47.254172.16.47.2554,094
4172.16.48.0/20172.16.48.1 to 172.16.63.254172.16.63.2554,094
5172.16.64.0/20172.16.64.1 to 172.16.79.254172.16.79.2554,094
6172.16.80.0/20172.16.80.1 to 172.16.95.254172.16.95.2554,094
7172.16.96.0/20172.16.96.1 to 172.16.111.254172.16.111.2554,094
8172.16.112.0/20172.16.112.1 to 172.16.127.254172.16.127.2554,094
9172.16.128.0/20172.16.128.1 to 172.16.143.254172.16.143.2554,094
10172.16.144.0/20172.16.144.1 to 172.16.159.254172.16.159.2554,094
11172.16.160.0/20172.16.160.1 to 172.16.175.254172.16.175.2554,094
12172.16.176.0/20172.16.176.1 to 172.16.191.254172.16.191.2554,094
13172.16.192.0/20172.16.192.1 to 172.16.207.254172.16.207.2554,094
14172.16.208.0/20172.16.208.1 to 172.16.223.254172.16.223.2554,094
15172.16.224.0/20172.16.224.1 to 172.16.239.254172.16.239.2554,094
16172.16.240.0/20172.16.240.1 to 172.16.255.254172.16.255.2554,094
17172.17.0.0/20172.17.0.1 to 172.17.15.254172.17.15.2554,094
18172.17.16.0/20172.17.16.1 to 172.17.31.254172.17.31.2554,094
19172.17.32.0/20172.17.32.1 to 172.17.47.254172.17.47.2554,094
20172.17.48.0/20172.17.48.1 to 172.17.63.254172.17.63.2554,094
21172.17.64.0/20172.17.64.1 to 172.17.79.254172.17.79.2554,094
22172.17.80.0/20172.17.80.1 to 172.17.95.254172.17.95.2554,094
23172.17.96.0/20172.17.96.1 to 172.17.111.254172.17.111.2554,094
24172.17.112.0/20172.17.112.1 to 172.17.127.254172.17.127.2554,094
25172.17.128.0/20172.17.128.1 to 172.17.143.254172.17.143.2554,094
26172.17.144.0/20172.17.144.1 to 172.17.159.254172.17.159.2554,094
27172.17.160.0/20172.17.160.1 to 172.17.175.254172.17.175.2554,094
28172.17.176.0/20172.17.176.1 to 172.17.191.254172.17.191.2554,094
29172.17.192.0/20172.17.192.1 to 172.17.207.254172.17.207.2554,094
30172.17.208.0/20172.17.208.1 to 172.17.223.254172.17.223.2554,094
31172.17.224.0/20172.17.224.1 to 172.17.239.254172.17.239.2554,094
32172.17.240.0/20172.17.240.1 to 172.17.255.254172.17.255.2554,094
33172.18.0.0/20172.18.0.1 to 172.18.15.254172.18.15.2554,094
34172.18.16.0/20172.18.16.1 to 172.18.31.254172.18.31.2554,094
35172.18.32.0/20172.18.32.1 to 172.18.47.254172.18.47.2554,094
36172.18.48.0/20172.18.48.1 to 172.18.63.254172.18.63.2554,094
37172.18.64.0/20172.18.64.1 to 172.18.79.254172.18.79.2554,094
38172.18.80.0/20172.18.80.1 to 172.18.95.254172.18.95.2554,094
39172.18.96.0/20172.18.96.1 to 172.18.111.254172.18.111.2554,094
40172.18.112.0/20172.18.112.1 to 172.18.127.254172.18.127.2554,094
41172.18.128.0/20172.18.128.1 to 172.18.143.254172.18.143.2554,094
42172.18.144.0/20172.18.144.1 to 172.18.159.254172.18.159.2554,094
43172.18.160.0/20172.18.160.1 to 172.18.175.254172.18.175.2554,094
44172.18.176.0/20172.18.176.1 to 172.18.191.254172.18.191.2554,094
45172.18.192.0/20172.18.192.1 to 172.18.207.254172.18.207.2554,094
46172.18.208.0/20172.18.208.1 to 172.18.223.254172.18.223.2554,094
47172.18.224.0/20172.18.224.1 to 172.18.239.254172.18.239.2554,094
48172.18.240.0/20172.18.240.1 to 172.18.255.254172.18.255.2554,094
49172.19.0.0/20172.19.0.1 to 172.19.15.254172.19.15.2554,094
50172.19.16.0/20172.19.16.1 to 172.19.31.254172.19.31.2554,094
51172.19.32.0/20172.19.32.1 to 172.19.47.254172.19.47.2554,094
52172.19.48.0/20172.19.48.1 to 172.19.63.254172.19.63.2554,094
53172.19.64.0/20172.19.64.1 to 172.19.79.254172.19.79.2554,094
54172.19.80.0/20172.19.80.1 to 172.19.95.254172.19.95.2554,094
55172.19.96.0/20172.19.96.1 to 172.19.111.254172.19.111.2554,094
56172.19.112.0/20172.19.112.1 to 172.19.127.254172.19.127.2554,094
57172.19.128.0/20172.19.128.1 to 172.19.143.254172.19.143.2554,094
58172.19.144.0/20172.19.144.1 to 172.19.159.254172.19.159.2554,094
59172.19.160.0/20172.19.160.1 to 172.19.175.254172.19.175.2554,094
60172.19.176.0/20172.19.176.1 to 172.19.191.254172.19.191.2554,094
61172.19.192.0/20172.19.192.1 to 172.19.207.254172.19.207.2554,094
62172.19.208.0/20172.19.208.1 to 172.19.223.254172.19.223.2554,094
63172.19.224.0/20172.19.224.1 to 172.19.239.254172.19.239.2554,094
64172.19.240.0/20172.19.240.1 to 172.19.255.254172.19.255.2554,094
65172.20.0.0/20172.20.0.1 to 172.20.15.254172.20.15.2554,094
66172.20.16.0/20172.20.16.1 to 172.20.31.254172.20.31.2554,094
67172.20.32.0/20172.20.32.1 to 172.20.47.254172.20.47.2554,094
68172.20.48.0/20172.20.48.1 to 172.20.63.254172.20.63.2554,094
69172.20.64.0/20172.20.64.1 to 172.20.79.254172.20.79.2554,094
70172.20.80.0/20172.20.80.1 to 172.20.95.254172.20.95.2554,094
71172.20.96.0/20172.20.96.1 to 172.20.111.254172.20.111.2554,094
72172.20.112.0/20172.20.112.1 to 172.20.127.254172.20.127.2554,094
73172.20.128.0/20172.20.128.1 to 172.20.143.254172.20.143.2554,094
74172.20.144.0/20172.20.144.1 to 172.20.159.254172.20.159.2554,094
75172.20.160.0/20172.20.160.1 to 172.20.175.254172.20.175.2554,094
76172.20.176.0/20172.20.176.1 to 172.20.191.254172.20.191.2554,094
77172.20.192.0/20172.20.192.1 to 172.20.207.254172.20.207.2554,094
78172.20.208.0/20172.20.208.1 to 172.20.223.254172.20.223.2554,094
79172.20.224.0/20172.20.224.1 to 172.20.239.254172.20.239.2554,094
80172.20.240.0/20172.20.240.1 to 172.20.255.254172.20.255.2554,094
81172.21.0.0/20172.21.0.1 to 172.21.15.254172.21.15.2554,094
82172.21.16.0/20172.21.16.1 to 172.21.31.254172.21.31.2554,094
83172.21.32.0/20172.21.32.1 to 172.21.47.254172.21.47.2554,094
84172.21.48.0/20172.21.48.1 to 172.21.63.254172.21.63.2554,094
85172.21.64.0/20172.21.64.1 to 172.21.79.254172.21.79.2554,094
86172.21.80.0/20172.21.80.1 to 172.21.95.254172.21.95.2554,094
87172.21.96.0/20172.21.96.1 to 172.21.111.254172.21.111.2554,094
88172.21.112.0/20172.21.112.1 to 172.21.127.254172.21.127.2554,094
89172.21.128.0/20172.21.128.1 to 172.21.143.254172.21.143.2554,094
90172.21.144.0/20172.21.144.1 to 172.21.159.254172.21.159.2554,094
91172.21.160.0/20172.21.160.1 to 172.21.175.254172.21.175.2554,094
92172.21.176.0/20172.21.176.1 to 172.21.191.254172.21.191.2554,094
93172.21.192.0/20172.21.192.1 to 172.21.207.254172.21.207.2554,094
94172.21.208.0/20172.21.208.1 to 172.21.223.254172.21.223.2554,094
95172.21.224.0/20172.21.224.1 to 172.21.239.254172.21.239.2554,094
96172.21.240.0/20172.21.240.1 to 172.21.255.254172.21.255.2554,094
97172.22.0.0/20172.22.0.1 to 172.22.15.254172.22.15.2554,094
98172.22.16.0/20172.22.16.1 to 172.22.31.254172.22.31.2554,094
99172.22.32.0/20172.22.32.1 to 172.22.47.254172.22.47.2554,094
100172.22.48.0/20172.22.48.1 to 172.22.63.254172.22.63.2554,094
101172.22.64.0/20172.22.64.1 to 172.22.79.254172.22.79.2554,094
102172.22.80.0/20172.22.80.1 to 172.22.95.254172.22.95.2554,094
103172.22.96.0/20172.22.96.1 to 172.22.111.254172.22.111.2554,094
104172.22.112.0/20172.22.112.1 to 172.22.127.254172.22.127.2554,094
105172.22.128.0/20172.22.128.1 to 172.22.143.254172.22.143.2554,094
106172.22.144.0/20172.22.144.1 to 172.22.159.254172.22.159.2554,094
107172.22.160.0/20172.22.160.1 to 172.22.175.254172.22.175.2554,094
108172.22.176.0/20172.22.176.1 to 172.22.191.254172.22.191.2554,094
109172.22.192.0/20172.22.192.1 to 172.22.207.254172.22.207.2554,094
110172.22.208.0/20172.22.208.1 to 172.22.223.254172.22.223.2554,094
111172.22.224.0/20172.22.224.1 to 172.22.239.254172.22.239.2554,094
112172.22.240.0/20172.22.240.1 to 172.22.255.254172.22.255.2554,094
113172.23.0.0/20172.23.0.1 to 172.23.15.254172.23.15.2554,094
114172.23.16.0/20172.23.16.1 to 172.23.31.254172.23.31.2554,094
115172.23.32.0/20172.23.32.1 to 172.23.47.254172.23.47.2554,094
116172.23.48.0/20172.23.48.1 to 172.23.63.254172.23.63.2554,094
117172.23.64.0/20172.23.64.1 to 172.23.79.254172.23.79.2554,094
118172.23.80.0/20172.23.80.1 to 172.23.95.254172.23.95.2554,094
119172.23.96.0/20172.23.96.1 to 172.23.111.254172.23.111.2554,094
120172.23.112.0/20172.23.112.1 to 172.23.127.254172.23.127.2554,094
121172.23.128.0/20172.23.128.1 to 172.23.143.254172.23.143.2554,094
122172.23.144.0/20172.23.144.1 to 172.23.159.254172.23.159.2554,094
123172.23.160.0/20172.23.160.1 to 172.23.175.254172.23.175.2554,094
124172.23.176.0/20172.23.176.1 to 172.23.191.254172.23.191.2554,094
125172.23.192.0/20172.23.192.1 to 172.23.207.254172.23.207.2554,094
126172.23.208.0/20172.23.208.1 to 172.23.223.254172.23.223.2554,094
127172.23.224.0/20172.23.224.1 to 172.23.239.254172.23.239.2554,094
128172.23.240.0/20172.23.240.1 to 172.23.255.254172.23.255.2554,094
129172.24.0.0/20172.24.0.1 to 172.24.15.254172.24.15.2554,094
130172.24.16.0/20172.24.16.1 to 172.24.31.254172.24.31.2554,094
131172.24.32.0/20172.24.32.1 to 172.24.47.254172.24.47.2554,094
132172.24.48.0/20172.24.48.1 to 172.24.63.254172.24.63.2554,094
133172.24.64.0/20172.24.64.1 to 172.24.79.254172.24.79.2554,094
134172.24.80.0/20172.24.80.1 to 172.24.95.254172.24.95.2554,094
135172.24.96.0/20172.24.96.1 to 172.24.111.254172.24.111.2554,094
136172.24.112.0/20172.24.112.1 to 172.24.127.254172.24.127.2554,094
137172.24.128.0/20172.24.128.1 to 172.24.143.254172.24.143.2554,094
138172.24.144.0/20172.24.144.1 to 172.24.159.254172.24.159.2554,094
139172.24.160.0/20172.24.160.1 to 172.24.175.254172.24.175.2554,094
140172.24.176.0/20172.24.176.1 to 172.24.191.254172.24.191.2554,094
141172.24.192.0/20172.24.192.1 to 172.24.207.254172.24.207.2554,094
142172.24.208.0/20172.24.208.1 to 172.24.223.254172.24.223.2554,094
143172.24.224.0/20172.24.224.1 to 172.24.239.254172.24.239.2554,094
144172.24.240.0/20172.24.240.1 to 172.24.255.254172.24.255.2554,094
145172.25.0.0/20172.25.0.1 to 172.25.15.254172.25.15.2554,094
146172.25.16.0/20172.25.16.1 to 172.25.31.254172.25.31.2554,094
147172.25.32.0/20172.25.32.1 to 172.25.47.254172.25.47.2554,094
148172.25.48.0/20172.25.48.1 to 172.25.63.254172.25.63.2554,094
149172.25.64.0/20172.25.64.1 to 172.25.79.254172.25.79.2554,094
150172.25.80.0/20172.25.80.1 to 172.25.95.254172.25.95.2554,094
151172.25.96.0/20172.25.96.1 to 172.25.111.254172.25.111.2554,094
152172.25.112.0/20172.25.112.1 to 172.25.127.254172.25.127.2554,094
153172.25.128.0/20172.25.128.1 to 172.25.143.254172.25.143.2554,094
154172.25.144.0/20172.25.144.1 to 172.25.159.254172.25.159.2554,094
155172.25.160.0/20172.25.160.1 to 172.25.175.254172.25.175.2554,094
156172.25.176.0/20172.25.176.1 to 172.25.191.254172.25.191.2554,094
157172.25.192.0/20172.25.192.1 to 172.25.207.254172.25.207.2554,094
158172.25.208.0/20172.25.208.1 to 172.25.223.254172.25.223.2554,094
159172.25.224.0/20172.25.224.1 to 172.25.239.254172.25.239.2554,094
160172.25.240.0/20172.25.240.1 to 172.25.255.254172.25.255.2554,094
161172.26.0.0/20172.26.0.1 to 172.26.15.254172.26.15.2554,094
162172.26.16.0/20172.26.16.1 to 172.26.31.254172.26.31.2554,094
163172.26.32.0/20172.26.32.1 to 172.26.47.254172.26.47.2554,094
164172.26.48.0/20172.26.48.1 to 172.26.63.254172.26.63.2554,094
165172.26.64.0/20172.26.64.1 to 172.26.79.254172.26.79.2554,094
166172.26.80.0/20172.26.80.1 to 172.26.95.254172.26.95.2554,094
167172.26.96.0/20172.26.96.1 to 172.26.111.254172.26.111.2554,094
168172.26.112.0/20172.26.112.1 to 172.26.127.254172.26.127.2554,094
169172.26.128.0/20172.26.128.1 to 172.26.143.254172.26.143.2554,094
170172.26.144.0/20172.26.144.1 to 172.26.159.254172.26.159.2554,094
171172.26.160.0/20172.26.160.1 to 172.26.175.254172.26.175.2554,094
172172.26.176.0/20172.26.176.1 to 172.26.191.254172.26.191.2554,094
173172.26.192.0/20172.26.192.1 to 172.26.207.254172.26.207.2554,094
174172.26.208.0/20172.26.208.1 to 172.26.223.254172.26.223.2554,094
175172.26.224.0/20172.26.224.1 to 172.26.239.254172.26.239.2554,094
176172.26.240.0/20172.26.240.1 to 172.26.255.254172.26.255.2554,094
177172.27.0.0/20172.27.0.1 to 172.27.15.254172.27.15.2554,094
178172.27.16.0/20172.27.16.1 to 172.27.31.254172.27.31.2554,094
179172.27.32.0/20172.27.32.1 to 172.27.47.254172.27.47.2554,094
180172.27.48.0/20172.27.48.1 to 172.27.63.254172.27.63.2554,094
181172.27.64.0/20172.27.64.1 to 172.27.79.254172.27.79.2554,094
182172.27.80.0/20172.27.80.1 to 172.27.95.254172.27.95.2554,094
183172.27.96.0/20172.27.96.1 to 172.27.111.254172.27.111.2554,094
184172.27.112.0/20172.27.112.1 to 172.27.127.254172.27.127.2554,094
185172.27.128.0/20172.27.128.1 to 172.27.143.254172.27.143.2554,094
186172.27.144.0/20172.27.144.1 to 172.27.159.254172.27.159.2554,094
187172.27.160.0/20172.27.160.1 to 172.27.175.254172.27.175.2554,094
188172.27.176.0/20172.27.176.1 to 172.27.191.254172.27.191.2554,094
189172.27.192.0/20172.27.192.1 to 172.27.207.254172.27.207.2554,094
190172.27.208.0/20172.27.208.1 to 172.27.223.254172.27.223.2554,094
191172.27.224.0/20172.27.224.1 to 172.27.239.254172.27.239.2554,094
192172.27.240.0/20172.27.240.1 to 172.27.255.254172.27.255.2554,094
193172.28.0.0/20172.28.0.1 to 172.28.15.254172.28.15.2554,094
194172.28.16.0/20172.28.16.1 to 172.28.31.254172.28.31.2554,094
195172.28.32.0/20172.28.32.1 to 172.28.47.254172.28.47.2554,094
196172.28.48.0/20172.28.48.1 to 172.28.63.254172.28.63.2554,094
197172.28.64.0/20172.28.64.1 to 172.28.79.254172.28.79.2554,094
198172.28.80.0/20172.28.80.1 to 172.28.95.254172.28.95.2554,094
199172.28.96.0/20172.28.96.1 to 172.28.111.254172.28.111.2554,094
200172.28.112.0/20172.28.112.1 to 172.28.127.254172.28.127.2554,094
201172.28.128.0/20172.28.128.1 to 172.28.143.254172.28.143.2554,094
202172.28.144.0/20172.28.144.1 to 172.28.159.254172.28.159.2554,094
203172.28.160.0/20172.28.160.1 to 172.28.175.254172.28.175.2554,094
204172.28.176.0/20172.28.176.1 to 172.28.191.254172.28.191.2554,094
205172.28.192.0/20172.28.192.1 to 172.28.207.254172.28.207.2554,094
206172.28.208.0/20172.28.208.1 to 172.28.223.254172.28.223.2554,094
207172.28.224.0/20172.28.224.1 to 172.28.239.254172.28.239.2554,094
208172.28.240.0/20172.28.240.1 to 172.28.255.254172.28.255.2554,094
209172.29.0.0/20172.29.0.1 to 172.29.15.254172.29.15.2554,094
210172.29.16.0/20172.29.16.1 to 172.29.31.254172.29.31.2554,094
211172.29.32.0/20172.29.32.1 to 172.29.47.254172.29.47.2554,094
212172.29.48.0/20172.29.48.1 to 172.29.63.254172.29.63.2554,094
213172.29.64.0/20172.29.64.1 to 172.29.79.254172.29.79.2554,094
214172.29.80.0/20172.29.80.1 to 172.29.95.254172.29.95.2554,094
215172.29.96.0/20172.29.96.1 to 172.29.111.254172.29.111.2554,094
216172.29.112.0/20172.29.112.1 to 172.29.127.254172.29.127.2554,094
217172.29.128.0/20172.29.128.1 to 172.29.143.254172.29.143.2554,094
218172.29.144.0/20172.29.144.1 to 172.29.159.254172.29.159.2554,094
219172.29.160.0/20172.29.160.1 to 172.29.175.254172.29.175.2554,094
220172.29.176.0/20172.29.176.1 to 172.29.191.254172.29.191.2554,094
221172.29.192.0/20172.29.192.1 to 172.29.207.254172.29.207.2554,094
222172.29.208.0/20172.29.208.1 to 172.29.223.254172.29.223.2554,094
223172.29.224.0/20172.29.224.1 to 172.29.239.254172.29.239.2554,094
224172.29.240.0/20172.29.240.1 to 172.29.255.254172.29.255.2554,094
225172.30.0.0/20172.30.0.1 to 172.30.15.254172.30.15.2554,094
226172.30.16.0/20172.30.16.1 to 172.30.31.254172.30.31.2554,094
227172.30.32.0/20172.30.32.1 to 172.30.47.254172.30.47.2554,094
228172.30.48.0/20172.30.48.1 to 172.30.63.254172.30.63.2554,094
229172.30.64.0/20172.30.64.1 to 172.30.79.254172.30.79.2554,094
230172.30.80.0/20172.30.80.1 to 172.30.95.254172.30.95.2554,094
231172.30.96.0/20172.30.96.1 to 172.30.111.254172.30.111.2554,094
232172.30.112.0/20172.30.112.1 to 172.30.127.254172.30.127.2554,094
233172.30.128.0/20172.30.128.1 to 172.30.143.254172.30.143.2554,094
234172.30.144.0/20172.30.144.1 to 172.30.159.254172.30.159.2554,094
235172.30.160.0/20172.30.160.1 to 172.30.175.254172.30.175.2554,094
236172.30.176.0/20172.30.176.1 to 172.30.191.254172.30.191.2554,094
237172.30.192.0/20172.30.192.1 to 172.30.207.254172.30.207.2554,094
238172.30.208.0/20172.30.208.1 to 172.30.223.254172.30.223.2554,094
239172.30.224.0/20172.30.224.1 to 172.30.239.254172.30.239.2554,094
240172.30.240.0/20172.30.240.1 to 172.30.255.254172.30.255.2554,094
241172.31.0.0/20172.31.0.1 to 172.31.15.254172.31.15.2554,094
242172.31.16.0/20172.31.16.1 to 172.31.31.254172.31.31.2554,094
243172.31.32.0/20172.31.32.1 to 172.31.47.254172.31.47.2554,094
244172.31.48.0/20172.31.48.1 to 172.31.63.254172.31.63.2554,094
245172.31.64.0/20172.31.64.1 to 172.31.79.254172.31.79.2554,094
246172.31.80.0/20172.31.80.1 to 172.31.95.254172.31.95.2554,094
247172.31.96.0/20172.31.96.1 to 172.31.111.254172.31.111.2554,094
248172.31.112.0/20172.31.112.1 to 172.31.127.254172.31.127.2554,094
249172.31.128.0/20172.31.128.1 to 172.31.143.254172.31.143.2554,094
250172.31.144.0/20172.31.144.1 to 172.31.159.254172.31.159.2554,094
251172.31.160.0/20172.31.160.1 to 172.31.175.254172.31.175.2554,094
252172.31.176.0/20172.31.176.1 to 172.31.191.254172.31.191.2554,094
253172.31.192.0/20172.31.192.1 to 172.31.207.254172.31.207.2554,094
254172.31.208.0/20172.31.208.1 to 172.31.223.254172.31.223.2554,094
255172.31.224.0/20172.31.224.1 to 172.31.239.254172.31.239.2554,094
256172.31.240.0/20172.31.240.1 to 172.31.255.254172.31.255.2554,094

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.