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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.

Network205.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
205.0.0.0
Broadcast address
205.255.255.255
First usable
205.0.0.1
Last usable
205.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
Public public
Old class
C (default /24)
As numbers
Hex CD000000 · Integer 3439329280 to 3456106495
Reverse DNS zone
205.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11001101..00000000.00000000.00000000205.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network11001101..00000000.00000000.00000000205.0.0.0
Broadcast11001101..11111111.11111111.11111111205.255.255.255
Split into smaller subnets/20
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

205.0.0.0/8 makes 4,096 subnets of /20; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1205.0.0.0/20205.0.0.1 to 205.0.15.254205.0.15.2554,094
2205.0.16.0/20205.0.16.1 to 205.0.31.254205.0.31.2554,094
3205.0.32.0/20205.0.32.1 to 205.0.47.254205.0.47.2554,094
4205.0.48.0/20205.0.48.1 to 205.0.63.254205.0.63.2554,094
5205.0.64.0/20205.0.64.1 to 205.0.79.254205.0.79.2554,094
6205.0.80.0/20205.0.80.1 to 205.0.95.254205.0.95.2554,094
7205.0.96.0/20205.0.96.1 to 205.0.111.254205.0.111.2554,094
8205.0.112.0/20205.0.112.1 to 205.0.127.254205.0.127.2554,094
9205.0.128.0/20205.0.128.1 to 205.0.143.254205.0.143.2554,094
10205.0.144.0/20205.0.144.1 to 205.0.159.254205.0.159.2554,094
11205.0.160.0/20205.0.160.1 to 205.0.175.254205.0.175.2554,094
12205.0.176.0/20205.0.176.1 to 205.0.191.254205.0.191.2554,094
13205.0.192.0/20205.0.192.1 to 205.0.207.254205.0.207.2554,094
14205.0.208.0/20205.0.208.1 to 205.0.223.254205.0.223.2554,094
15205.0.224.0/20205.0.224.1 to 205.0.239.254205.0.239.2554,094
16205.0.240.0/20205.0.240.1 to 205.0.255.254205.0.255.2554,094
17205.1.0.0/20205.1.0.1 to 205.1.15.254205.1.15.2554,094
18205.1.16.0/20205.1.16.1 to 205.1.31.254205.1.31.2554,094
19205.1.32.0/20205.1.32.1 to 205.1.47.254205.1.47.2554,094
20205.1.48.0/20205.1.48.1 to 205.1.63.254205.1.63.2554,094
21205.1.64.0/20205.1.64.1 to 205.1.79.254205.1.79.2554,094
22205.1.80.0/20205.1.80.1 to 205.1.95.254205.1.95.2554,094
23205.1.96.0/20205.1.96.1 to 205.1.111.254205.1.111.2554,094
24205.1.112.0/20205.1.112.1 to 205.1.127.254205.1.127.2554,094
25205.1.128.0/20205.1.128.1 to 205.1.143.254205.1.143.2554,094
26205.1.144.0/20205.1.144.1 to 205.1.159.254205.1.159.2554,094
27205.1.160.0/20205.1.160.1 to 205.1.175.254205.1.175.2554,094
28205.1.176.0/20205.1.176.1 to 205.1.191.254205.1.191.2554,094
29205.1.192.0/20205.1.192.1 to 205.1.207.254205.1.207.2554,094
30205.1.208.0/20205.1.208.1 to 205.1.223.254205.1.223.2554,094
31205.1.224.0/20205.1.224.1 to 205.1.239.254205.1.239.2554,094
32205.1.240.0/20205.1.240.1 to 205.1.255.254205.1.255.2554,094
33205.2.0.0/20205.2.0.1 to 205.2.15.254205.2.15.2554,094
34205.2.16.0/20205.2.16.1 to 205.2.31.254205.2.31.2554,094
35205.2.32.0/20205.2.32.1 to 205.2.47.254205.2.47.2554,094
36205.2.48.0/20205.2.48.1 to 205.2.63.254205.2.63.2554,094
37205.2.64.0/20205.2.64.1 to 205.2.79.254205.2.79.2554,094
38205.2.80.0/20205.2.80.1 to 205.2.95.254205.2.95.2554,094
39205.2.96.0/20205.2.96.1 to 205.2.111.254205.2.111.2554,094
40205.2.112.0/20205.2.112.1 to 205.2.127.254205.2.127.2554,094
41205.2.128.0/20205.2.128.1 to 205.2.143.254205.2.143.2554,094
42205.2.144.0/20205.2.144.1 to 205.2.159.254205.2.159.2554,094
43205.2.160.0/20205.2.160.1 to 205.2.175.254205.2.175.2554,094
44205.2.176.0/20205.2.176.1 to 205.2.191.254205.2.191.2554,094
45205.2.192.0/20205.2.192.1 to 205.2.207.254205.2.207.2554,094
46205.2.208.0/20205.2.208.1 to 205.2.223.254205.2.223.2554,094
47205.2.224.0/20205.2.224.1 to 205.2.239.254205.2.239.2554,094
48205.2.240.0/20205.2.240.1 to 205.2.255.254205.2.255.2554,094
49205.3.0.0/20205.3.0.1 to 205.3.15.254205.3.15.2554,094
50205.3.16.0/20205.3.16.1 to 205.3.31.254205.3.31.2554,094
51205.3.32.0/20205.3.32.1 to 205.3.47.254205.3.47.2554,094
52205.3.48.0/20205.3.48.1 to 205.3.63.254205.3.63.2554,094
53205.3.64.0/20205.3.64.1 to 205.3.79.254205.3.79.2554,094
54205.3.80.0/20205.3.80.1 to 205.3.95.254205.3.95.2554,094
55205.3.96.0/20205.3.96.1 to 205.3.111.254205.3.111.2554,094
56205.3.112.0/20205.3.112.1 to 205.3.127.254205.3.127.2554,094
57205.3.128.0/20205.3.128.1 to 205.3.143.254205.3.143.2554,094
58205.3.144.0/20205.3.144.1 to 205.3.159.254205.3.159.2554,094
59205.3.160.0/20205.3.160.1 to 205.3.175.254205.3.175.2554,094
60205.3.176.0/20205.3.176.1 to 205.3.191.254205.3.191.2554,094
61205.3.192.0/20205.3.192.1 to 205.3.207.254205.3.207.2554,094
62205.3.208.0/20205.3.208.1 to 205.3.223.254205.3.223.2554,094
63205.3.224.0/20205.3.224.1 to 205.3.239.254205.3.239.2554,094
64205.3.240.0/20205.3.240.1 to 205.3.255.254205.3.255.2554,094
65205.4.0.0/20205.4.0.1 to 205.4.15.254205.4.15.2554,094
66205.4.16.0/20205.4.16.1 to 205.4.31.254205.4.31.2554,094
67205.4.32.0/20205.4.32.1 to 205.4.47.254205.4.47.2554,094
68205.4.48.0/20205.4.48.1 to 205.4.63.254205.4.63.2554,094
69205.4.64.0/20205.4.64.1 to 205.4.79.254205.4.79.2554,094
70205.4.80.0/20205.4.80.1 to 205.4.95.254205.4.95.2554,094
71205.4.96.0/20205.4.96.1 to 205.4.111.254205.4.111.2554,094
72205.4.112.0/20205.4.112.1 to 205.4.127.254205.4.127.2554,094
73205.4.128.0/20205.4.128.1 to 205.4.143.254205.4.143.2554,094
74205.4.144.0/20205.4.144.1 to 205.4.159.254205.4.159.2554,094
75205.4.160.0/20205.4.160.1 to 205.4.175.254205.4.175.2554,094
76205.4.176.0/20205.4.176.1 to 205.4.191.254205.4.191.2554,094
77205.4.192.0/20205.4.192.1 to 205.4.207.254205.4.207.2554,094
78205.4.208.0/20205.4.208.1 to 205.4.223.254205.4.223.2554,094
79205.4.224.0/20205.4.224.1 to 205.4.239.254205.4.239.2554,094
80205.4.240.0/20205.4.240.1 to 205.4.255.254205.4.255.2554,094
81205.5.0.0/20205.5.0.1 to 205.5.15.254205.5.15.2554,094
82205.5.16.0/20205.5.16.1 to 205.5.31.254205.5.31.2554,094
83205.5.32.0/20205.5.32.1 to 205.5.47.254205.5.47.2554,094
84205.5.48.0/20205.5.48.1 to 205.5.63.254205.5.63.2554,094
85205.5.64.0/20205.5.64.1 to 205.5.79.254205.5.79.2554,094
86205.5.80.0/20205.5.80.1 to 205.5.95.254205.5.95.2554,094
87205.5.96.0/20205.5.96.1 to 205.5.111.254205.5.111.2554,094
88205.5.112.0/20205.5.112.1 to 205.5.127.254205.5.127.2554,094
89205.5.128.0/20205.5.128.1 to 205.5.143.254205.5.143.2554,094
90205.5.144.0/20205.5.144.1 to 205.5.159.254205.5.159.2554,094
91205.5.160.0/20205.5.160.1 to 205.5.175.254205.5.175.2554,094
92205.5.176.0/20205.5.176.1 to 205.5.191.254205.5.191.2554,094
93205.5.192.0/20205.5.192.1 to 205.5.207.254205.5.207.2554,094
94205.5.208.0/20205.5.208.1 to 205.5.223.254205.5.223.2554,094
95205.5.224.0/20205.5.224.1 to 205.5.239.254205.5.239.2554,094
96205.5.240.0/20205.5.240.1 to 205.5.255.254205.5.255.2554,094
97205.6.0.0/20205.6.0.1 to 205.6.15.254205.6.15.2554,094
98205.6.16.0/20205.6.16.1 to 205.6.31.254205.6.31.2554,094
99205.6.32.0/20205.6.32.1 to 205.6.47.254205.6.47.2554,094
100205.6.48.0/20205.6.48.1 to 205.6.63.254205.6.63.2554,094
101205.6.64.0/20205.6.64.1 to 205.6.79.254205.6.79.2554,094
102205.6.80.0/20205.6.80.1 to 205.6.95.254205.6.95.2554,094
103205.6.96.0/20205.6.96.1 to 205.6.111.254205.6.111.2554,094
104205.6.112.0/20205.6.112.1 to 205.6.127.254205.6.127.2554,094
105205.6.128.0/20205.6.128.1 to 205.6.143.254205.6.143.2554,094
106205.6.144.0/20205.6.144.1 to 205.6.159.254205.6.159.2554,094
107205.6.160.0/20205.6.160.1 to 205.6.175.254205.6.175.2554,094
108205.6.176.0/20205.6.176.1 to 205.6.191.254205.6.191.2554,094
109205.6.192.0/20205.6.192.1 to 205.6.207.254205.6.207.2554,094
110205.6.208.0/20205.6.208.1 to 205.6.223.254205.6.223.2554,094
111205.6.224.0/20205.6.224.1 to 205.6.239.254205.6.239.2554,094
112205.6.240.0/20205.6.240.1 to 205.6.255.254205.6.255.2554,094
113205.7.0.0/20205.7.0.1 to 205.7.15.254205.7.15.2554,094
114205.7.16.0/20205.7.16.1 to 205.7.31.254205.7.31.2554,094
115205.7.32.0/20205.7.32.1 to 205.7.47.254205.7.47.2554,094
116205.7.48.0/20205.7.48.1 to 205.7.63.254205.7.63.2554,094
117205.7.64.0/20205.7.64.1 to 205.7.79.254205.7.79.2554,094
118205.7.80.0/20205.7.80.1 to 205.7.95.254205.7.95.2554,094
119205.7.96.0/20205.7.96.1 to 205.7.111.254205.7.111.2554,094
120205.7.112.0/20205.7.112.1 to 205.7.127.254205.7.127.2554,094
121205.7.128.0/20205.7.128.1 to 205.7.143.254205.7.143.2554,094
122205.7.144.0/20205.7.144.1 to 205.7.159.254205.7.159.2554,094
123205.7.160.0/20205.7.160.1 to 205.7.175.254205.7.175.2554,094
124205.7.176.0/20205.7.176.1 to 205.7.191.254205.7.191.2554,094
125205.7.192.0/20205.7.192.1 to 205.7.207.254205.7.207.2554,094
126205.7.208.0/20205.7.208.1 to 205.7.223.254205.7.223.2554,094
127205.7.224.0/20205.7.224.1 to 205.7.239.254205.7.239.2554,094
128205.7.240.0/20205.7.240.1 to 205.7.255.254205.7.255.2554,094
129205.8.0.0/20205.8.0.1 to 205.8.15.254205.8.15.2554,094
130205.8.16.0/20205.8.16.1 to 205.8.31.254205.8.31.2554,094
131205.8.32.0/20205.8.32.1 to 205.8.47.254205.8.47.2554,094
132205.8.48.0/20205.8.48.1 to 205.8.63.254205.8.63.2554,094
133205.8.64.0/20205.8.64.1 to 205.8.79.254205.8.79.2554,094
134205.8.80.0/20205.8.80.1 to 205.8.95.254205.8.95.2554,094
135205.8.96.0/20205.8.96.1 to 205.8.111.254205.8.111.2554,094
136205.8.112.0/20205.8.112.1 to 205.8.127.254205.8.127.2554,094
137205.8.128.0/20205.8.128.1 to 205.8.143.254205.8.143.2554,094
138205.8.144.0/20205.8.144.1 to 205.8.159.254205.8.159.2554,094
139205.8.160.0/20205.8.160.1 to 205.8.175.254205.8.175.2554,094
140205.8.176.0/20205.8.176.1 to 205.8.191.254205.8.191.2554,094
141205.8.192.0/20205.8.192.1 to 205.8.207.254205.8.207.2554,094
142205.8.208.0/20205.8.208.1 to 205.8.223.254205.8.223.2554,094
143205.8.224.0/20205.8.224.1 to 205.8.239.254205.8.239.2554,094
144205.8.240.0/20205.8.240.1 to 205.8.255.254205.8.255.2554,094
145205.9.0.0/20205.9.0.1 to 205.9.15.254205.9.15.2554,094
146205.9.16.0/20205.9.16.1 to 205.9.31.254205.9.31.2554,094
147205.9.32.0/20205.9.32.1 to 205.9.47.254205.9.47.2554,094
148205.9.48.0/20205.9.48.1 to 205.9.63.254205.9.63.2554,094
149205.9.64.0/20205.9.64.1 to 205.9.79.254205.9.79.2554,094
150205.9.80.0/20205.9.80.1 to 205.9.95.254205.9.95.2554,094
151205.9.96.0/20205.9.96.1 to 205.9.111.254205.9.111.2554,094
152205.9.112.0/20205.9.112.1 to 205.9.127.254205.9.127.2554,094
153205.9.128.0/20205.9.128.1 to 205.9.143.254205.9.143.2554,094
154205.9.144.0/20205.9.144.1 to 205.9.159.254205.9.159.2554,094
155205.9.160.0/20205.9.160.1 to 205.9.175.254205.9.175.2554,094
156205.9.176.0/20205.9.176.1 to 205.9.191.254205.9.191.2554,094
157205.9.192.0/20205.9.192.1 to 205.9.207.254205.9.207.2554,094
158205.9.208.0/20205.9.208.1 to 205.9.223.254205.9.223.2554,094
159205.9.224.0/20205.9.224.1 to 205.9.239.254205.9.239.2554,094
160205.9.240.0/20205.9.240.1 to 205.9.255.254205.9.255.2554,094
161205.10.0.0/20205.10.0.1 to 205.10.15.254205.10.15.2554,094
162205.10.16.0/20205.10.16.1 to 205.10.31.254205.10.31.2554,094
163205.10.32.0/20205.10.32.1 to 205.10.47.254205.10.47.2554,094
164205.10.48.0/20205.10.48.1 to 205.10.63.254205.10.63.2554,094
165205.10.64.0/20205.10.64.1 to 205.10.79.254205.10.79.2554,094
166205.10.80.0/20205.10.80.1 to 205.10.95.254205.10.95.2554,094
167205.10.96.0/20205.10.96.1 to 205.10.111.254205.10.111.2554,094
168205.10.112.0/20205.10.112.1 to 205.10.127.254205.10.127.2554,094
169205.10.128.0/20205.10.128.1 to 205.10.143.254205.10.143.2554,094
170205.10.144.0/20205.10.144.1 to 205.10.159.254205.10.159.2554,094
171205.10.160.0/20205.10.160.1 to 205.10.175.254205.10.175.2554,094
172205.10.176.0/20205.10.176.1 to 205.10.191.254205.10.191.2554,094
173205.10.192.0/20205.10.192.1 to 205.10.207.254205.10.207.2554,094
174205.10.208.0/20205.10.208.1 to 205.10.223.254205.10.223.2554,094
175205.10.224.0/20205.10.224.1 to 205.10.239.254205.10.239.2554,094
176205.10.240.0/20205.10.240.1 to 205.10.255.254205.10.255.2554,094
177205.11.0.0/20205.11.0.1 to 205.11.15.254205.11.15.2554,094
178205.11.16.0/20205.11.16.1 to 205.11.31.254205.11.31.2554,094
179205.11.32.0/20205.11.32.1 to 205.11.47.254205.11.47.2554,094
180205.11.48.0/20205.11.48.1 to 205.11.63.254205.11.63.2554,094
181205.11.64.0/20205.11.64.1 to 205.11.79.254205.11.79.2554,094
182205.11.80.0/20205.11.80.1 to 205.11.95.254205.11.95.2554,094
183205.11.96.0/20205.11.96.1 to 205.11.111.254205.11.111.2554,094
184205.11.112.0/20205.11.112.1 to 205.11.127.254205.11.127.2554,094
185205.11.128.0/20205.11.128.1 to 205.11.143.254205.11.143.2554,094
186205.11.144.0/20205.11.144.1 to 205.11.159.254205.11.159.2554,094
187205.11.160.0/20205.11.160.1 to 205.11.175.254205.11.175.2554,094
188205.11.176.0/20205.11.176.1 to 205.11.191.254205.11.191.2554,094
189205.11.192.0/20205.11.192.1 to 205.11.207.254205.11.207.2554,094
190205.11.208.0/20205.11.208.1 to 205.11.223.254205.11.223.2554,094
191205.11.224.0/20205.11.224.1 to 205.11.239.254205.11.239.2554,094
192205.11.240.0/20205.11.240.1 to 205.11.255.254205.11.255.2554,094
193205.12.0.0/20205.12.0.1 to 205.12.15.254205.12.15.2554,094
194205.12.16.0/20205.12.16.1 to 205.12.31.254205.12.31.2554,094
195205.12.32.0/20205.12.32.1 to 205.12.47.254205.12.47.2554,094
196205.12.48.0/20205.12.48.1 to 205.12.63.254205.12.63.2554,094
197205.12.64.0/20205.12.64.1 to 205.12.79.254205.12.79.2554,094
198205.12.80.0/20205.12.80.1 to 205.12.95.254205.12.95.2554,094
199205.12.96.0/20205.12.96.1 to 205.12.111.254205.12.111.2554,094
200205.12.112.0/20205.12.112.1 to 205.12.127.254205.12.127.2554,094
201205.12.128.0/20205.12.128.1 to 205.12.143.254205.12.143.2554,094
202205.12.144.0/20205.12.144.1 to 205.12.159.254205.12.159.2554,094
203205.12.160.0/20205.12.160.1 to 205.12.175.254205.12.175.2554,094
204205.12.176.0/20205.12.176.1 to 205.12.191.254205.12.191.2554,094
205205.12.192.0/20205.12.192.1 to 205.12.207.254205.12.207.2554,094
206205.12.208.0/20205.12.208.1 to 205.12.223.254205.12.223.2554,094
207205.12.224.0/20205.12.224.1 to 205.12.239.254205.12.239.2554,094
208205.12.240.0/20205.12.240.1 to 205.12.255.254205.12.255.2554,094
209205.13.0.0/20205.13.0.1 to 205.13.15.254205.13.15.2554,094
210205.13.16.0/20205.13.16.1 to 205.13.31.254205.13.31.2554,094
211205.13.32.0/20205.13.32.1 to 205.13.47.254205.13.47.2554,094
212205.13.48.0/20205.13.48.1 to 205.13.63.254205.13.63.2554,094
213205.13.64.0/20205.13.64.1 to 205.13.79.254205.13.79.2554,094
214205.13.80.0/20205.13.80.1 to 205.13.95.254205.13.95.2554,094
215205.13.96.0/20205.13.96.1 to 205.13.111.254205.13.111.2554,094
216205.13.112.0/20205.13.112.1 to 205.13.127.254205.13.127.2554,094
217205.13.128.0/20205.13.128.1 to 205.13.143.254205.13.143.2554,094
218205.13.144.0/20205.13.144.1 to 205.13.159.254205.13.159.2554,094
219205.13.160.0/20205.13.160.1 to 205.13.175.254205.13.175.2554,094
220205.13.176.0/20205.13.176.1 to 205.13.191.254205.13.191.2554,094
221205.13.192.0/20205.13.192.1 to 205.13.207.254205.13.207.2554,094
222205.13.208.0/20205.13.208.1 to 205.13.223.254205.13.223.2554,094
223205.13.224.0/20205.13.224.1 to 205.13.239.254205.13.239.2554,094
224205.13.240.0/20205.13.240.1 to 205.13.255.254205.13.255.2554,094
225205.14.0.0/20205.14.0.1 to 205.14.15.254205.14.15.2554,094
226205.14.16.0/20205.14.16.1 to 205.14.31.254205.14.31.2554,094
227205.14.32.0/20205.14.32.1 to 205.14.47.254205.14.47.2554,094
228205.14.48.0/20205.14.48.1 to 205.14.63.254205.14.63.2554,094
229205.14.64.0/20205.14.64.1 to 205.14.79.254205.14.79.2554,094
230205.14.80.0/20205.14.80.1 to 205.14.95.254205.14.95.2554,094
231205.14.96.0/20205.14.96.1 to 205.14.111.254205.14.111.2554,094
232205.14.112.0/20205.14.112.1 to 205.14.127.254205.14.127.2554,094
233205.14.128.0/20205.14.128.1 to 205.14.143.254205.14.143.2554,094
234205.14.144.0/20205.14.144.1 to 205.14.159.254205.14.159.2554,094
235205.14.160.0/20205.14.160.1 to 205.14.175.254205.14.175.2554,094
236205.14.176.0/20205.14.176.1 to 205.14.191.254205.14.191.2554,094
237205.14.192.0/20205.14.192.1 to 205.14.207.254205.14.207.2554,094
238205.14.208.0/20205.14.208.1 to 205.14.223.254205.14.223.2554,094
239205.14.224.0/20205.14.224.1 to 205.14.239.254205.14.239.2554,094
240205.14.240.0/20205.14.240.1 to 205.14.255.254205.14.255.2554,094
241205.15.0.0/20205.15.0.1 to 205.15.15.254205.15.15.2554,094
242205.15.16.0/20205.15.16.1 to 205.15.31.254205.15.31.2554,094
243205.15.32.0/20205.15.32.1 to 205.15.47.254205.15.47.2554,094
244205.15.48.0/20205.15.48.1 to 205.15.63.254205.15.63.2554,094
245205.15.64.0/20205.15.64.1 to 205.15.79.254205.15.79.2554,094
246205.15.80.0/20205.15.80.1 to 205.15.95.254205.15.95.2554,094
247205.15.96.0/20205.15.96.1 to 205.15.111.254205.15.111.2554,094
248205.15.112.0/20205.15.112.1 to 205.15.127.254205.15.127.2554,094
249205.15.128.0/20205.15.128.1 to 205.15.143.254205.15.143.2554,094
250205.15.144.0/20205.15.144.1 to 205.15.159.254205.15.159.2554,094
251205.15.160.0/20205.15.160.1 to 205.15.175.254205.15.175.2554,094
252205.15.176.0/20205.15.176.1 to 205.15.191.254205.15.191.2554,094
253205.15.192.0/20205.15.192.1 to 205.15.207.254205.15.207.2554,094
254205.15.208.0/20205.15.208.1 to 205.15.223.254205.15.223.2554,094
255205.15.224.0/20205.15.224.1 to 205.15.239.254205.15.239.2554,094
256205.15.240.0/20205.15.240.1 to 205.15.255.254205.15.255.2554,094

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.