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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.

Network203.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
203.0.0.0
Broadcast address
203.255.255.255
First usable
203.0.0.1
Last usable
203.255.255.254
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 CB000000 · Integer 3405774848 to 3422552063
Reverse DNS zone
203.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11001011..00000000.00000000.00000000203.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network11001011..00000000.00000000.00000000203.0.0.0
Broadcast11001011..11111111.11111111.11111111203.255.255.255
Split into smaller subnets/19
/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)

203.0.0.0/8 makes 2,048 subnets of /19; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1203.0.0.0/19203.0.0.1 to 203.0.31.254203.0.31.2558,190
2203.0.32.0/19203.0.32.1 to 203.0.63.254203.0.63.2558,190
3203.0.64.0/19203.0.64.1 to 203.0.95.254203.0.95.2558,190
4203.0.96.0/19203.0.96.1 to 203.0.127.254203.0.127.2558,190
5203.0.128.0/19203.0.128.1 to 203.0.159.254203.0.159.2558,190
6203.0.160.0/19203.0.160.1 to 203.0.191.254203.0.191.2558,190
7203.0.192.0/19203.0.192.1 to 203.0.223.254203.0.223.2558,190
8203.0.224.0/19203.0.224.1 to 203.0.255.254203.0.255.2558,190
9203.1.0.0/19203.1.0.1 to 203.1.31.254203.1.31.2558,190
10203.1.32.0/19203.1.32.1 to 203.1.63.254203.1.63.2558,190
11203.1.64.0/19203.1.64.1 to 203.1.95.254203.1.95.2558,190
12203.1.96.0/19203.1.96.1 to 203.1.127.254203.1.127.2558,190
13203.1.128.0/19203.1.128.1 to 203.1.159.254203.1.159.2558,190
14203.1.160.0/19203.1.160.1 to 203.1.191.254203.1.191.2558,190
15203.1.192.0/19203.1.192.1 to 203.1.223.254203.1.223.2558,190
16203.1.224.0/19203.1.224.1 to 203.1.255.254203.1.255.2558,190
17203.2.0.0/19203.2.0.1 to 203.2.31.254203.2.31.2558,190
18203.2.32.0/19203.2.32.1 to 203.2.63.254203.2.63.2558,190
19203.2.64.0/19203.2.64.1 to 203.2.95.254203.2.95.2558,190
20203.2.96.0/19203.2.96.1 to 203.2.127.254203.2.127.2558,190
21203.2.128.0/19203.2.128.1 to 203.2.159.254203.2.159.2558,190
22203.2.160.0/19203.2.160.1 to 203.2.191.254203.2.191.2558,190
23203.2.192.0/19203.2.192.1 to 203.2.223.254203.2.223.2558,190
24203.2.224.0/19203.2.224.1 to 203.2.255.254203.2.255.2558,190
25203.3.0.0/19203.3.0.1 to 203.3.31.254203.3.31.2558,190
26203.3.32.0/19203.3.32.1 to 203.3.63.254203.3.63.2558,190
27203.3.64.0/19203.3.64.1 to 203.3.95.254203.3.95.2558,190
28203.3.96.0/19203.3.96.1 to 203.3.127.254203.3.127.2558,190
29203.3.128.0/19203.3.128.1 to 203.3.159.254203.3.159.2558,190
30203.3.160.0/19203.3.160.1 to 203.3.191.254203.3.191.2558,190
31203.3.192.0/19203.3.192.1 to 203.3.223.254203.3.223.2558,190
32203.3.224.0/19203.3.224.1 to 203.3.255.254203.3.255.2558,190
33203.4.0.0/19203.4.0.1 to 203.4.31.254203.4.31.2558,190
34203.4.32.0/19203.4.32.1 to 203.4.63.254203.4.63.2558,190
35203.4.64.0/19203.4.64.1 to 203.4.95.254203.4.95.2558,190
36203.4.96.0/19203.4.96.1 to 203.4.127.254203.4.127.2558,190
37203.4.128.0/19203.4.128.1 to 203.4.159.254203.4.159.2558,190
38203.4.160.0/19203.4.160.1 to 203.4.191.254203.4.191.2558,190
39203.4.192.0/19203.4.192.1 to 203.4.223.254203.4.223.2558,190
40203.4.224.0/19203.4.224.1 to 203.4.255.254203.4.255.2558,190
41203.5.0.0/19203.5.0.1 to 203.5.31.254203.5.31.2558,190
42203.5.32.0/19203.5.32.1 to 203.5.63.254203.5.63.2558,190
43203.5.64.0/19203.5.64.1 to 203.5.95.254203.5.95.2558,190
44203.5.96.0/19203.5.96.1 to 203.5.127.254203.5.127.2558,190
45203.5.128.0/19203.5.128.1 to 203.5.159.254203.5.159.2558,190
46203.5.160.0/19203.5.160.1 to 203.5.191.254203.5.191.2558,190
47203.5.192.0/19203.5.192.1 to 203.5.223.254203.5.223.2558,190
48203.5.224.0/19203.5.224.1 to 203.5.255.254203.5.255.2558,190
49203.6.0.0/19203.6.0.1 to 203.6.31.254203.6.31.2558,190
50203.6.32.0/19203.6.32.1 to 203.6.63.254203.6.63.2558,190
51203.6.64.0/19203.6.64.1 to 203.6.95.254203.6.95.2558,190
52203.6.96.0/19203.6.96.1 to 203.6.127.254203.6.127.2558,190
53203.6.128.0/19203.6.128.1 to 203.6.159.254203.6.159.2558,190
54203.6.160.0/19203.6.160.1 to 203.6.191.254203.6.191.2558,190
55203.6.192.0/19203.6.192.1 to 203.6.223.254203.6.223.2558,190
56203.6.224.0/19203.6.224.1 to 203.6.255.254203.6.255.2558,190
57203.7.0.0/19203.7.0.1 to 203.7.31.254203.7.31.2558,190
58203.7.32.0/19203.7.32.1 to 203.7.63.254203.7.63.2558,190
59203.7.64.0/19203.7.64.1 to 203.7.95.254203.7.95.2558,190
60203.7.96.0/19203.7.96.1 to 203.7.127.254203.7.127.2558,190
61203.7.128.0/19203.7.128.1 to 203.7.159.254203.7.159.2558,190
62203.7.160.0/19203.7.160.1 to 203.7.191.254203.7.191.2558,190
63203.7.192.0/19203.7.192.1 to 203.7.223.254203.7.223.2558,190
64203.7.224.0/19203.7.224.1 to 203.7.255.254203.7.255.2558,190
65203.8.0.0/19203.8.0.1 to 203.8.31.254203.8.31.2558,190
66203.8.32.0/19203.8.32.1 to 203.8.63.254203.8.63.2558,190
67203.8.64.0/19203.8.64.1 to 203.8.95.254203.8.95.2558,190
68203.8.96.0/19203.8.96.1 to 203.8.127.254203.8.127.2558,190
69203.8.128.0/19203.8.128.1 to 203.8.159.254203.8.159.2558,190
70203.8.160.0/19203.8.160.1 to 203.8.191.254203.8.191.2558,190
71203.8.192.0/19203.8.192.1 to 203.8.223.254203.8.223.2558,190
72203.8.224.0/19203.8.224.1 to 203.8.255.254203.8.255.2558,190
73203.9.0.0/19203.9.0.1 to 203.9.31.254203.9.31.2558,190
74203.9.32.0/19203.9.32.1 to 203.9.63.254203.9.63.2558,190
75203.9.64.0/19203.9.64.1 to 203.9.95.254203.9.95.2558,190
76203.9.96.0/19203.9.96.1 to 203.9.127.254203.9.127.2558,190
77203.9.128.0/19203.9.128.1 to 203.9.159.254203.9.159.2558,190
78203.9.160.0/19203.9.160.1 to 203.9.191.254203.9.191.2558,190
79203.9.192.0/19203.9.192.1 to 203.9.223.254203.9.223.2558,190
80203.9.224.0/19203.9.224.1 to 203.9.255.254203.9.255.2558,190
81203.10.0.0/19203.10.0.1 to 203.10.31.254203.10.31.2558,190
82203.10.32.0/19203.10.32.1 to 203.10.63.254203.10.63.2558,190
83203.10.64.0/19203.10.64.1 to 203.10.95.254203.10.95.2558,190
84203.10.96.0/19203.10.96.1 to 203.10.127.254203.10.127.2558,190
85203.10.128.0/19203.10.128.1 to 203.10.159.254203.10.159.2558,190
86203.10.160.0/19203.10.160.1 to 203.10.191.254203.10.191.2558,190
87203.10.192.0/19203.10.192.1 to 203.10.223.254203.10.223.2558,190
88203.10.224.0/19203.10.224.1 to 203.10.255.254203.10.255.2558,190
89203.11.0.0/19203.11.0.1 to 203.11.31.254203.11.31.2558,190
90203.11.32.0/19203.11.32.1 to 203.11.63.254203.11.63.2558,190
91203.11.64.0/19203.11.64.1 to 203.11.95.254203.11.95.2558,190
92203.11.96.0/19203.11.96.1 to 203.11.127.254203.11.127.2558,190
93203.11.128.0/19203.11.128.1 to 203.11.159.254203.11.159.2558,190
94203.11.160.0/19203.11.160.1 to 203.11.191.254203.11.191.2558,190
95203.11.192.0/19203.11.192.1 to 203.11.223.254203.11.223.2558,190
96203.11.224.0/19203.11.224.1 to 203.11.255.254203.11.255.2558,190
97203.12.0.0/19203.12.0.1 to 203.12.31.254203.12.31.2558,190
98203.12.32.0/19203.12.32.1 to 203.12.63.254203.12.63.2558,190
99203.12.64.0/19203.12.64.1 to 203.12.95.254203.12.95.2558,190
100203.12.96.0/19203.12.96.1 to 203.12.127.254203.12.127.2558,190
101203.12.128.0/19203.12.128.1 to 203.12.159.254203.12.159.2558,190
102203.12.160.0/19203.12.160.1 to 203.12.191.254203.12.191.2558,190
103203.12.192.0/19203.12.192.1 to 203.12.223.254203.12.223.2558,190
104203.12.224.0/19203.12.224.1 to 203.12.255.254203.12.255.2558,190
105203.13.0.0/19203.13.0.1 to 203.13.31.254203.13.31.2558,190
106203.13.32.0/19203.13.32.1 to 203.13.63.254203.13.63.2558,190
107203.13.64.0/19203.13.64.1 to 203.13.95.254203.13.95.2558,190
108203.13.96.0/19203.13.96.1 to 203.13.127.254203.13.127.2558,190
109203.13.128.0/19203.13.128.1 to 203.13.159.254203.13.159.2558,190
110203.13.160.0/19203.13.160.1 to 203.13.191.254203.13.191.2558,190
111203.13.192.0/19203.13.192.1 to 203.13.223.254203.13.223.2558,190
112203.13.224.0/19203.13.224.1 to 203.13.255.254203.13.255.2558,190
113203.14.0.0/19203.14.0.1 to 203.14.31.254203.14.31.2558,190
114203.14.32.0/19203.14.32.1 to 203.14.63.254203.14.63.2558,190
115203.14.64.0/19203.14.64.1 to 203.14.95.254203.14.95.2558,190
116203.14.96.0/19203.14.96.1 to 203.14.127.254203.14.127.2558,190
117203.14.128.0/19203.14.128.1 to 203.14.159.254203.14.159.2558,190
118203.14.160.0/19203.14.160.1 to 203.14.191.254203.14.191.2558,190
119203.14.192.0/19203.14.192.1 to 203.14.223.254203.14.223.2558,190
120203.14.224.0/19203.14.224.1 to 203.14.255.254203.14.255.2558,190
121203.15.0.0/19203.15.0.1 to 203.15.31.254203.15.31.2558,190
122203.15.32.0/19203.15.32.1 to 203.15.63.254203.15.63.2558,190
123203.15.64.0/19203.15.64.1 to 203.15.95.254203.15.95.2558,190
124203.15.96.0/19203.15.96.1 to 203.15.127.254203.15.127.2558,190
125203.15.128.0/19203.15.128.1 to 203.15.159.254203.15.159.2558,190
126203.15.160.0/19203.15.160.1 to 203.15.191.254203.15.191.2558,190
127203.15.192.0/19203.15.192.1 to 203.15.223.254203.15.223.2558,190
128203.15.224.0/19203.15.224.1 to 203.15.255.254203.15.255.2558,190
129203.16.0.0/19203.16.0.1 to 203.16.31.254203.16.31.2558,190
130203.16.32.0/19203.16.32.1 to 203.16.63.254203.16.63.2558,190
131203.16.64.0/19203.16.64.1 to 203.16.95.254203.16.95.2558,190
132203.16.96.0/19203.16.96.1 to 203.16.127.254203.16.127.2558,190
133203.16.128.0/19203.16.128.1 to 203.16.159.254203.16.159.2558,190
134203.16.160.0/19203.16.160.1 to 203.16.191.254203.16.191.2558,190
135203.16.192.0/19203.16.192.1 to 203.16.223.254203.16.223.2558,190
136203.16.224.0/19203.16.224.1 to 203.16.255.254203.16.255.2558,190
137203.17.0.0/19203.17.0.1 to 203.17.31.254203.17.31.2558,190
138203.17.32.0/19203.17.32.1 to 203.17.63.254203.17.63.2558,190
139203.17.64.0/19203.17.64.1 to 203.17.95.254203.17.95.2558,190
140203.17.96.0/19203.17.96.1 to 203.17.127.254203.17.127.2558,190
141203.17.128.0/19203.17.128.1 to 203.17.159.254203.17.159.2558,190
142203.17.160.0/19203.17.160.1 to 203.17.191.254203.17.191.2558,190
143203.17.192.0/19203.17.192.1 to 203.17.223.254203.17.223.2558,190
144203.17.224.0/19203.17.224.1 to 203.17.255.254203.17.255.2558,190
145203.18.0.0/19203.18.0.1 to 203.18.31.254203.18.31.2558,190
146203.18.32.0/19203.18.32.1 to 203.18.63.254203.18.63.2558,190
147203.18.64.0/19203.18.64.1 to 203.18.95.254203.18.95.2558,190
148203.18.96.0/19203.18.96.1 to 203.18.127.254203.18.127.2558,190
149203.18.128.0/19203.18.128.1 to 203.18.159.254203.18.159.2558,190
150203.18.160.0/19203.18.160.1 to 203.18.191.254203.18.191.2558,190
151203.18.192.0/19203.18.192.1 to 203.18.223.254203.18.223.2558,190
152203.18.224.0/19203.18.224.1 to 203.18.255.254203.18.255.2558,190
153203.19.0.0/19203.19.0.1 to 203.19.31.254203.19.31.2558,190
154203.19.32.0/19203.19.32.1 to 203.19.63.254203.19.63.2558,190
155203.19.64.0/19203.19.64.1 to 203.19.95.254203.19.95.2558,190
156203.19.96.0/19203.19.96.1 to 203.19.127.254203.19.127.2558,190
157203.19.128.0/19203.19.128.1 to 203.19.159.254203.19.159.2558,190
158203.19.160.0/19203.19.160.1 to 203.19.191.254203.19.191.2558,190
159203.19.192.0/19203.19.192.1 to 203.19.223.254203.19.223.2558,190
160203.19.224.0/19203.19.224.1 to 203.19.255.254203.19.255.2558,190
161203.20.0.0/19203.20.0.1 to 203.20.31.254203.20.31.2558,190
162203.20.32.0/19203.20.32.1 to 203.20.63.254203.20.63.2558,190
163203.20.64.0/19203.20.64.1 to 203.20.95.254203.20.95.2558,190
164203.20.96.0/19203.20.96.1 to 203.20.127.254203.20.127.2558,190
165203.20.128.0/19203.20.128.1 to 203.20.159.254203.20.159.2558,190
166203.20.160.0/19203.20.160.1 to 203.20.191.254203.20.191.2558,190
167203.20.192.0/19203.20.192.1 to 203.20.223.254203.20.223.2558,190
168203.20.224.0/19203.20.224.1 to 203.20.255.254203.20.255.2558,190
169203.21.0.0/19203.21.0.1 to 203.21.31.254203.21.31.2558,190
170203.21.32.0/19203.21.32.1 to 203.21.63.254203.21.63.2558,190
171203.21.64.0/19203.21.64.1 to 203.21.95.254203.21.95.2558,190
172203.21.96.0/19203.21.96.1 to 203.21.127.254203.21.127.2558,190
173203.21.128.0/19203.21.128.1 to 203.21.159.254203.21.159.2558,190
174203.21.160.0/19203.21.160.1 to 203.21.191.254203.21.191.2558,190
175203.21.192.0/19203.21.192.1 to 203.21.223.254203.21.223.2558,190
176203.21.224.0/19203.21.224.1 to 203.21.255.254203.21.255.2558,190
177203.22.0.0/19203.22.0.1 to 203.22.31.254203.22.31.2558,190
178203.22.32.0/19203.22.32.1 to 203.22.63.254203.22.63.2558,190
179203.22.64.0/19203.22.64.1 to 203.22.95.254203.22.95.2558,190
180203.22.96.0/19203.22.96.1 to 203.22.127.254203.22.127.2558,190
181203.22.128.0/19203.22.128.1 to 203.22.159.254203.22.159.2558,190
182203.22.160.0/19203.22.160.1 to 203.22.191.254203.22.191.2558,190
183203.22.192.0/19203.22.192.1 to 203.22.223.254203.22.223.2558,190
184203.22.224.0/19203.22.224.1 to 203.22.255.254203.22.255.2558,190
185203.23.0.0/19203.23.0.1 to 203.23.31.254203.23.31.2558,190
186203.23.32.0/19203.23.32.1 to 203.23.63.254203.23.63.2558,190
187203.23.64.0/19203.23.64.1 to 203.23.95.254203.23.95.2558,190
188203.23.96.0/19203.23.96.1 to 203.23.127.254203.23.127.2558,190
189203.23.128.0/19203.23.128.1 to 203.23.159.254203.23.159.2558,190
190203.23.160.0/19203.23.160.1 to 203.23.191.254203.23.191.2558,190
191203.23.192.0/19203.23.192.1 to 203.23.223.254203.23.223.2558,190
192203.23.224.0/19203.23.224.1 to 203.23.255.254203.23.255.2558,190
193203.24.0.0/19203.24.0.1 to 203.24.31.254203.24.31.2558,190
194203.24.32.0/19203.24.32.1 to 203.24.63.254203.24.63.2558,190
195203.24.64.0/19203.24.64.1 to 203.24.95.254203.24.95.2558,190
196203.24.96.0/19203.24.96.1 to 203.24.127.254203.24.127.2558,190
197203.24.128.0/19203.24.128.1 to 203.24.159.254203.24.159.2558,190
198203.24.160.0/19203.24.160.1 to 203.24.191.254203.24.191.2558,190
199203.24.192.0/19203.24.192.1 to 203.24.223.254203.24.223.2558,190
200203.24.224.0/19203.24.224.1 to 203.24.255.254203.24.255.2558,190
201203.25.0.0/19203.25.0.1 to 203.25.31.254203.25.31.2558,190
202203.25.32.0/19203.25.32.1 to 203.25.63.254203.25.63.2558,190
203203.25.64.0/19203.25.64.1 to 203.25.95.254203.25.95.2558,190
204203.25.96.0/19203.25.96.1 to 203.25.127.254203.25.127.2558,190
205203.25.128.0/19203.25.128.1 to 203.25.159.254203.25.159.2558,190
206203.25.160.0/19203.25.160.1 to 203.25.191.254203.25.191.2558,190
207203.25.192.0/19203.25.192.1 to 203.25.223.254203.25.223.2558,190
208203.25.224.0/19203.25.224.1 to 203.25.255.254203.25.255.2558,190
209203.26.0.0/19203.26.0.1 to 203.26.31.254203.26.31.2558,190
210203.26.32.0/19203.26.32.1 to 203.26.63.254203.26.63.2558,190
211203.26.64.0/19203.26.64.1 to 203.26.95.254203.26.95.2558,190
212203.26.96.0/19203.26.96.1 to 203.26.127.254203.26.127.2558,190
213203.26.128.0/19203.26.128.1 to 203.26.159.254203.26.159.2558,190
214203.26.160.0/19203.26.160.1 to 203.26.191.254203.26.191.2558,190
215203.26.192.0/19203.26.192.1 to 203.26.223.254203.26.223.2558,190
216203.26.224.0/19203.26.224.1 to 203.26.255.254203.26.255.2558,190
217203.27.0.0/19203.27.0.1 to 203.27.31.254203.27.31.2558,190
218203.27.32.0/19203.27.32.1 to 203.27.63.254203.27.63.2558,190
219203.27.64.0/19203.27.64.1 to 203.27.95.254203.27.95.2558,190
220203.27.96.0/19203.27.96.1 to 203.27.127.254203.27.127.2558,190
221203.27.128.0/19203.27.128.1 to 203.27.159.254203.27.159.2558,190
222203.27.160.0/19203.27.160.1 to 203.27.191.254203.27.191.2558,190
223203.27.192.0/19203.27.192.1 to 203.27.223.254203.27.223.2558,190
224203.27.224.0/19203.27.224.1 to 203.27.255.254203.27.255.2558,190
225203.28.0.0/19203.28.0.1 to 203.28.31.254203.28.31.2558,190
226203.28.32.0/19203.28.32.1 to 203.28.63.254203.28.63.2558,190
227203.28.64.0/19203.28.64.1 to 203.28.95.254203.28.95.2558,190
228203.28.96.0/19203.28.96.1 to 203.28.127.254203.28.127.2558,190
229203.28.128.0/19203.28.128.1 to 203.28.159.254203.28.159.2558,190
230203.28.160.0/19203.28.160.1 to 203.28.191.254203.28.191.2558,190
231203.28.192.0/19203.28.192.1 to 203.28.223.254203.28.223.2558,190
232203.28.224.0/19203.28.224.1 to 203.28.255.254203.28.255.2558,190
233203.29.0.0/19203.29.0.1 to 203.29.31.254203.29.31.2558,190
234203.29.32.0/19203.29.32.1 to 203.29.63.254203.29.63.2558,190
235203.29.64.0/19203.29.64.1 to 203.29.95.254203.29.95.2558,190
236203.29.96.0/19203.29.96.1 to 203.29.127.254203.29.127.2558,190
237203.29.128.0/19203.29.128.1 to 203.29.159.254203.29.159.2558,190
238203.29.160.0/19203.29.160.1 to 203.29.191.254203.29.191.2558,190
239203.29.192.0/19203.29.192.1 to 203.29.223.254203.29.223.2558,190
240203.29.224.0/19203.29.224.1 to 203.29.255.254203.29.255.2558,190
241203.30.0.0/19203.30.0.1 to 203.30.31.254203.30.31.2558,190
242203.30.32.0/19203.30.32.1 to 203.30.63.254203.30.63.2558,190
243203.30.64.0/19203.30.64.1 to 203.30.95.254203.30.95.2558,190
244203.30.96.0/19203.30.96.1 to 203.30.127.254203.30.127.2558,190
245203.30.128.0/19203.30.128.1 to 203.30.159.254203.30.159.2558,190
246203.30.160.0/19203.30.160.1 to 203.30.191.254203.30.191.2558,190
247203.30.192.0/19203.30.192.1 to 203.30.223.254203.30.223.2558,190
248203.30.224.0/19203.30.224.1 to 203.30.255.254203.30.255.2558,190
249203.31.0.0/19203.31.0.1 to 203.31.31.254203.31.31.2558,190
250203.31.32.0/19203.31.32.1 to 203.31.63.254203.31.63.2558,190
251203.31.64.0/19203.31.64.1 to 203.31.95.254203.31.95.2558,190
252203.31.96.0/19203.31.96.1 to 203.31.127.254203.31.127.2558,190
253203.31.128.0/19203.31.128.1 to 203.31.159.254203.31.159.2558,190
254203.31.160.0/19203.31.160.1 to 203.31.191.254203.31.191.2558,190
255203.31.192.0/19203.31.192.1 to 203.31.223.254203.31.223.2558,190
256203.31.224.0/19203.31.224.1 to 203.31.255.254203.31.255.2558,190

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.