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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.

Network251.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
251.0.0.0
Broadcast address
251.255.255.255
First usable
251.0.0.1
Last usable
251.255.255.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex FB000000 · Integer 4211081216 to 4227858431
Reverse DNS zone
251.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11111011..00000000.00000000.00000000251.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network11111011..00000000.00000000.00000000251.0.0.0
Broadcast11111011..11111111.11111111.11111111251.255.255.255
Split into smaller subnets/18
/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)

251.0.0.0/8 makes 1,024 subnets of /18; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1251.0.0.0/18251.0.0.1 to 251.0.63.254251.0.63.25516,382
2251.0.64.0/18251.0.64.1 to 251.0.127.254251.0.127.25516,382
3251.0.128.0/18251.0.128.1 to 251.0.191.254251.0.191.25516,382
4251.0.192.0/18251.0.192.1 to 251.0.255.254251.0.255.25516,382
5251.1.0.0/18251.1.0.1 to 251.1.63.254251.1.63.25516,382
6251.1.64.0/18251.1.64.1 to 251.1.127.254251.1.127.25516,382
7251.1.128.0/18251.1.128.1 to 251.1.191.254251.1.191.25516,382
8251.1.192.0/18251.1.192.1 to 251.1.255.254251.1.255.25516,382
9251.2.0.0/18251.2.0.1 to 251.2.63.254251.2.63.25516,382
10251.2.64.0/18251.2.64.1 to 251.2.127.254251.2.127.25516,382
11251.2.128.0/18251.2.128.1 to 251.2.191.254251.2.191.25516,382
12251.2.192.0/18251.2.192.1 to 251.2.255.254251.2.255.25516,382
13251.3.0.0/18251.3.0.1 to 251.3.63.254251.3.63.25516,382
14251.3.64.0/18251.3.64.1 to 251.3.127.254251.3.127.25516,382
15251.3.128.0/18251.3.128.1 to 251.3.191.254251.3.191.25516,382
16251.3.192.0/18251.3.192.1 to 251.3.255.254251.3.255.25516,382
17251.4.0.0/18251.4.0.1 to 251.4.63.254251.4.63.25516,382
18251.4.64.0/18251.4.64.1 to 251.4.127.254251.4.127.25516,382
19251.4.128.0/18251.4.128.1 to 251.4.191.254251.4.191.25516,382
20251.4.192.0/18251.4.192.1 to 251.4.255.254251.4.255.25516,382
21251.5.0.0/18251.5.0.1 to 251.5.63.254251.5.63.25516,382
22251.5.64.0/18251.5.64.1 to 251.5.127.254251.5.127.25516,382
23251.5.128.0/18251.5.128.1 to 251.5.191.254251.5.191.25516,382
24251.5.192.0/18251.5.192.1 to 251.5.255.254251.5.255.25516,382
25251.6.0.0/18251.6.0.1 to 251.6.63.254251.6.63.25516,382
26251.6.64.0/18251.6.64.1 to 251.6.127.254251.6.127.25516,382
27251.6.128.0/18251.6.128.1 to 251.6.191.254251.6.191.25516,382
28251.6.192.0/18251.6.192.1 to 251.6.255.254251.6.255.25516,382
29251.7.0.0/18251.7.0.1 to 251.7.63.254251.7.63.25516,382
30251.7.64.0/18251.7.64.1 to 251.7.127.254251.7.127.25516,382
31251.7.128.0/18251.7.128.1 to 251.7.191.254251.7.191.25516,382
32251.7.192.0/18251.7.192.1 to 251.7.255.254251.7.255.25516,382
33251.8.0.0/18251.8.0.1 to 251.8.63.254251.8.63.25516,382
34251.8.64.0/18251.8.64.1 to 251.8.127.254251.8.127.25516,382
35251.8.128.0/18251.8.128.1 to 251.8.191.254251.8.191.25516,382
36251.8.192.0/18251.8.192.1 to 251.8.255.254251.8.255.25516,382
37251.9.0.0/18251.9.0.1 to 251.9.63.254251.9.63.25516,382
38251.9.64.0/18251.9.64.1 to 251.9.127.254251.9.127.25516,382
39251.9.128.0/18251.9.128.1 to 251.9.191.254251.9.191.25516,382
40251.9.192.0/18251.9.192.1 to 251.9.255.254251.9.255.25516,382
41251.10.0.0/18251.10.0.1 to 251.10.63.254251.10.63.25516,382
42251.10.64.0/18251.10.64.1 to 251.10.127.254251.10.127.25516,382
43251.10.128.0/18251.10.128.1 to 251.10.191.254251.10.191.25516,382
44251.10.192.0/18251.10.192.1 to 251.10.255.254251.10.255.25516,382
45251.11.0.0/18251.11.0.1 to 251.11.63.254251.11.63.25516,382
46251.11.64.0/18251.11.64.1 to 251.11.127.254251.11.127.25516,382
47251.11.128.0/18251.11.128.1 to 251.11.191.254251.11.191.25516,382
48251.11.192.0/18251.11.192.1 to 251.11.255.254251.11.255.25516,382
49251.12.0.0/18251.12.0.1 to 251.12.63.254251.12.63.25516,382
50251.12.64.0/18251.12.64.1 to 251.12.127.254251.12.127.25516,382
51251.12.128.0/18251.12.128.1 to 251.12.191.254251.12.191.25516,382
52251.12.192.0/18251.12.192.1 to 251.12.255.254251.12.255.25516,382
53251.13.0.0/18251.13.0.1 to 251.13.63.254251.13.63.25516,382
54251.13.64.0/18251.13.64.1 to 251.13.127.254251.13.127.25516,382
55251.13.128.0/18251.13.128.1 to 251.13.191.254251.13.191.25516,382
56251.13.192.0/18251.13.192.1 to 251.13.255.254251.13.255.25516,382
57251.14.0.0/18251.14.0.1 to 251.14.63.254251.14.63.25516,382
58251.14.64.0/18251.14.64.1 to 251.14.127.254251.14.127.25516,382
59251.14.128.0/18251.14.128.1 to 251.14.191.254251.14.191.25516,382
60251.14.192.0/18251.14.192.1 to 251.14.255.254251.14.255.25516,382
61251.15.0.0/18251.15.0.1 to 251.15.63.254251.15.63.25516,382
62251.15.64.0/18251.15.64.1 to 251.15.127.254251.15.127.25516,382
63251.15.128.0/18251.15.128.1 to 251.15.191.254251.15.191.25516,382
64251.15.192.0/18251.15.192.1 to 251.15.255.254251.15.255.25516,382
65251.16.0.0/18251.16.0.1 to 251.16.63.254251.16.63.25516,382
66251.16.64.0/18251.16.64.1 to 251.16.127.254251.16.127.25516,382
67251.16.128.0/18251.16.128.1 to 251.16.191.254251.16.191.25516,382
68251.16.192.0/18251.16.192.1 to 251.16.255.254251.16.255.25516,382
69251.17.0.0/18251.17.0.1 to 251.17.63.254251.17.63.25516,382
70251.17.64.0/18251.17.64.1 to 251.17.127.254251.17.127.25516,382
71251.17.128.0/18251.17.128.1 to 251.17.191.254251.17.191.25516,382
72251.17.192.0/18251.17.192.1 to 251.17.255.254251.17.255.25516,382
73251.18.0.0/18251.18.0.1 to 251.18.63.254251.18.63.25516,382
74251.18.64.0/18251.18.64.1 to 251.18.127.254251.18.127.25516,382
75251.18.128.0/18251.18.128.1 to 251.18.191.254251.18.191.25516,382
76251.18.192.0/18251.18.192.1 to 251.18.255.254251.18.255.25516,382
77251.19.0.0/18251.19.0.1 to 251.19.63.254251.19.63.25516,382
78251.19.64.0/18251.19.64.1 to 251.19.127.254251.19.127.25516,382
79251.19.128.0/18251.19.128.1 to 251.19.191.254251.19.191.25516,382
80251.19.192.0/18251.19.192.1 to 251.19.255.254251.19.255.25516,382
81251.20.0.0/18251.20.0.1 to 251.20.63.254251.20.63.25516,382
82251.20.64.0/18251.20.64.1 to 251.20.127.254251.20.127.25516,382
83251.20.128.0/18251.20.128.1 to 251.20.191.254251.20.191.25516,382
84251.20.192.0/18251.20.192.1 to 251.20.255.254251.20.255.25516,382
85251.21.0.0/18251.21.0.1 to 251.21.63.254251.21.63.25516,382
86251.21.64.0/18251.21.64.1 to 251.21.127.254251.21.127.25516,382
87251.21.128.0/18251.21.128.1 to 251.21.191.254251.21.191.25516,382
88251.21.192.0/18251.21.192.1 to 251.21.255.254251.21.255.25516,382
89251.22.0.0/18251.22.0.1 to 251.22.63.254251.22.63.25516,382
90251.22.64.0/18251.22.64.1 to 251.22.127.254251.22.127.25516,382
91251.22.128.0/18251.22.128.1 to 251.22.191.254251.22.191.25516,382
92251.22.192.0/18251.22.192.1 to 251.22.255.254251.22.255.25516,382
93251.23.0.0/18251.23.0.1 to 251.23.63.254251.23.63.25516,382
94251.23.64.0/18251.23.64.1 to 251.23.127.254251.23.127.25516,382
95251.23.128.0/18251.23.128.1 to 251.23.191.254251.23.191.25516,382
96251.23.192.0/18251.23.192.1 to 251.23.255.254251.23.255.25516,382
97251.24.0.0/18251.24.0.1 to 251.24.63.254251.24.63.25516,382
98251.24.64.0/18251.24.64.1 to 251.24.127.254251.24.127.25516,382
99251.24.128.0/18251.24.128.1 to 251.24.191.254251.24.191.25516,382
100251.24.192.0/18251.24.192.1 to 251.24.255.254251.24.255.25516,382
101251.25.0.0/18251.25.0.1 to 251.25.63.254251.25.63.25516,382
102251.25.64.0/18251.25.64.1 to 251.25.127.254251.25.127.25516,382
103251.25.128.0/18251.25.128.1 to 251.25.191.254251.25.191.25516,382
104251.25.192.0/18251.25.192.1 to 251.25.255.254251.25.255.25516,382
105251.26.0.0/18251.26.0.1 to 251.26.63.254251.26.63.25516,382
106251.26.64.0/18251.26.64.1 to 251.26.127.254251.26.127.25516,382
107251.26.128.0/18251.26.128.1 to 251.26.191.254251.26.191.25516,382
108251.26.192.0/18251.26.192.1 to 251.26.255.254251.26.255.25516,382
109251.27.0.0/18251.27.0.1 to 251.27.63.254251.27.63.25516,382
110251.27.64.0/18251.27.64.1 to 251.27.127.254251.27.127.25516,382
111251.27.128.0/18251.27.128.1 to 251.27.191.254251.27.191.25516,382
112251.27.192.0/18251.27.192.1 to 251.27.255.254251.27.255.25516,382
113251.28.0.0/18251.28.0.1 to 251.28.63.254251.28.63.25516,382
114251.28.64.0/18251.28.64.1 to 251.28.127.254251.28.127.25516,382
115251.28.128.0/18251.28.128.1 to 251.28.191.254251.28.191.25516,382
116251.28.192.0/18251.28.192.1 to 251.28.255.254251.28.255.25516,382
117251.29.0.0/18251.29.0.1 to 251.29.63.254251.29.63.25516,382
118251.29.64.0/18251.29.64.1 to 251.29.127.254251.29.127.25516,382
119251.29.128.0/18251.29.128.1 to 251.29.191.254251.29.191.25516,382
120251.29.192.0/18251.29.192.1 to 251.29.255.254251.29.255.25516,382
121251.30.0.0/18251.30.0.1 to 251.30.63.254251.30.63.25516,382
122251.30.64.0/18251.30.64.1 to 251.30.127.254251.30.127.25516,382
123251.30.128.0/18251.30.128.1 to 251.30.191.254251.30.191.25516,382
124251.30.192.0/18251.30.192.1 to 251.30.255.254251.30.255.25516,382
125251.31.0.0/18251.31.0.1 to 251.31.63.254251.31.63.25516,382
126251.31.64.0/18251.31.64.1 to 251.31.127.254251.31.127.25516,382
127251.31.128.0/18251.31.128.1 to 251.31.191.254251.31.191.25516,382
128251.31.192.0/18251.31.192.1 to 251.31.255.254251.31.255.25516,382
129251.32.0.0/18251.32.0.1 to 251.32.63.254251.32.63.25516,382
130251.32.64.0/18251.32.64.1 to 251.32.127.254251.32.127.25516,382
131251.32.128.0/18251.32.128.1 to 251.32.191.254251.32.191.25516,382
132251.32.192.0/18251.32.192.1 to 251.32.255.254251.32.255.25516,382
133251.33.0.0/18251.33.0.1 to 251.33.63.254251.33.63.25516,382
134251.33.64.0/18251.33.64.1 to 251.33.127.254251.33.127.25516,382
135251.33.128.0/18251.33.128.1 to 251.33.191.254251.33.191.25516,382
136251.33.192.0/18251.33.192.1 to 251.33.255.254251.33.255.25516,382
137251.34.0.0/18251.34.0.1 to 251.34.63.254251.34.63.25516,382
138251.34.64.0/18251.34.64.1 to 251.34.127.254251.34.127.25516,382
139251.34.128.0/18251.34.128.1 to 251.34.191.254251.34.191.25516,382
140251.34.192.0/18251.34.192.1 to 251.34.255.254251.34.255.25516,382
141251.35.0.0/18251.35.0.1 to 251.35.63.254251.35.63.25516,382
142251.35.64.0/18251.35.64.1 to 251.35.127.254251.35.127.25516,382
143251.35.128.0/18251.35.128.1 to 251.35.191.254251.35.191.25516,382
144251.35.192.0/18251.35.192.1 to 251.35.255.254251.35.255.25516,382
145251.36.0.0/18251.36.0.1 to 251.36.63.254251.36.63.25516,382
146251.36.64.0/18251.36.64.1 to 251.36.127.254251.36.127.25516,382
147251.36.128.0/18251.36.128.1 to 251.36.191.254251.36.191.25516,382
148251.36.192.0/18251.36.192.1 to 251.36.255.254251.36.255.25516,382
149251.37.0.0/18251.37.0.1 to 251.37.63.254251.37.63.25516,382
150251.37.64.0/18251.37.64.1 to 251.37.127.254251.37.127.25516,382
151251.37.128.0/18251.37.128.1 to 251.37.191.254251.37.191.25516,382
152251.37.192.0/18251.37.192.1 to 251.37.255.254251.37.255.25516,382
153251.38.0.0/18251.38.0.1 to 251.38.63.254251.38.63.25516,382
154251.38.64.0/18251.38.64.1 to 251.38.127.254251.38.127.25516,382
155251.38.128.0/18251.38.128.1 to 251.38.191.254251.38.191.25516,382
156251.38.192.0/18251.38.192.1 to 251.38.255.254251.38.255.25516,382
157251.39.0.0/18251.39.0.1 to 251.39.63.254251.39.63.25516,382
158251.39.64.0/18251.39.64.1 to 251.39.127.254251.39.127.25516,382
159251.39.128.0/18251.39.128.1 to 251.39.191.254251.39.191.25516,382
160251.39.192.0/18251.39.192.1 to 251.39.255.254251.39.255.25516,382
161251.40.0.0/18251.40.0.1 to 251.40.63.254251.40.63.25516,382
162251.40.64.0/18251.40.64.1 to 251.40.127.254251.40.127.25516,382
163251.40.128.0/18251.40.128.1 to 251.40.191.254251.40.191.25516,382
164251.40.192.0/18251.40.192.1 to 251.40.255.254251.40.255.25516,382
165251.41.0.0/18251.41.0.1 to 251.41.63.254251.41.63.25516,382
166251.41.64.0/18251.41.64.1 to 251.41.127.254251.41.127.25516,382
167251.41.128.0/18251.41.128.1 to 251.41.191.254251.41.191.25516,382
168251.41.192.0/18251.41.192.1 to 251.41.255.254251.41.255.25516,382
169251.42.0.0/18251.42.0.1 to 251.42.63.254251.42.63.25516,382
170251.42.64.0/18251.42.64.1 to 251.42.127.254251.42.127.25516,382
171251.42.128.0/18251.42.128.1 to 251.42.191.254251.42.191.25516,382
172251.42.192.0/18251.42.192.1 to 251.42.255.254251.42.255.25516,382
173251.43.0.0/18251.43.0.1 to 251.43.63.254251.43.63.25516,382
174251.43.64.0/18251.43.64.1 to 251.43.127.254251.43.127.25516,382
175251.43.128.0/18251.43.128.1 to 251.43.191.254251.43.191.25516,382
176251.43.192.0/18251.43.192.1 to 251.43.255.254251.43.255.25516,382
177251.44.0.0/18251.44.0.1 to 251.44.63.254251.44.63.25516,382
178251.44.64.0/18251.44.64.1 to 251.44.127.254251.44.127.25516,382
179251.44.128.0/18251.44.128.1 to 251.44.191.254251.44.191.25516,382
180251.44.192.0/18251.44.192.1 to 251.44.255.254251.44.255.25516,382
181251.45.0.0/18251.45.0.1 to 251.45.63.254251.45.63.25516,382
182251.45.64.0/18251.45.64.1 to 251.45.127.254251.45.127.25516,382
183251.45.128.0/18251.45.128.1 to 251.45.191.254251.45.191.25516,382
184251.45.192.0/18251.45.192.1 to 251.45.255.254251.45.255.25516,382
185251.46.0.0/18251.46.0.1 to 251.46.63.254251.46.63.25516,382
186251.46.64.0/18251.46.64.1 to 251.46.127.254251.46.127.25516,382
187251.46.128.0/18251.46.128.1 to 251.46.191.254251.46.191.25516,382
188251.46.192.0/18251.46.192.1 to 251.46.255.254251.46.255.25516,382
189251.47.0.0/18251.47.0.1 to 251.47.63.254251.47.63.25516,382
190251.47.64.0/18251.47.64.1 to 251.47.127.254251.47.127.25516,382
191251.47.128.0/18251.47.128.1 to 251.47.191.254251.47.191.25516,382
192251.47.192.0/18251.47.192.1 to 251.47.255.254251.47.255.25516,382
193251.48.0.0/18251.48.0.1 to 251.48.63.254251.48.63.25516,382
194251.48.64.0/18251.48.64.1 to 251.48.127.254251.48.127.25516,382
195251.48.128.0/18251.48.128.1 to 251.48.191.254251.48.191.25516,382
196251.48.192.0/18251.48.192.1 to 251.48.255.254251.48.255.25516,382
197251.49.0.0/18251.49.0.1 to 251.49.63.254251.49.63.25516,382
198251.49.64.0/18251.49.64.1 to 251.49.127.254251.49.127.25516,382
199251.49.128.0/18251.49.128.1 to 251.49.191.254251.49.191.25516,382
200251.49.192.0/18251.49.192.1 to 251.49.255.254251.49.255.25516,382
201251.50.0.0/18251.50.0.1 to 251.50.63.254251.50.63.25516,382
202251.50.64.0/18251.50.64.1 to 251.50.127.254251.50.127.25516,382
203251.50.128.0/18251.50.128.1 to 251.50.191.254251.50.191.25516,382
204251.50.192.0/18251.50.192.1 to 251.50.255.254251.50.255.25516,382
205251.51.0.0/18251.51.0.1 to 251.51.63.254251.51.63.25516,382
206251.51.64.0/18251.51.64.1 to 251.51.127.254251.51.127.25516,382
207251.51.128.0/18251.51.128.1 to 251.51.191.254251.51.191.25516,382
208251.51.192.0/18251.51.192.1 to 251.51.255.254251.51.255.25516,382
209251.52.0.0/18251.52.0.1 to 251.52.63.254251.52.63.25516,382
210251.52.64.0/18251.52.64.1 to 251.52.127.254251.52.127.25516,382
211251.52.128.0/18251.52.128.1 to 251.52.191.254251.52.191.25516,382
212251.52.192.0/18251.52.192.1 to 251.52.255.254251.52.255.25516,382
213251.53.0.0/18251.53.0.1 to 251.53.63.254251.53.63.25516,382
214251.53.64.0/18251.53.64.1 to 251.53.127.254251.53.127.25516,382
215251.53.128.0/18251.53.128.1 to 251.53.191.254251.53.191.25516,382
216251.53.192.0/18251.53.192.1 to 251.53.255.254251.53.255.25516,382
217251.54.0.0/18251.54.0.1 to 251.54.63.254251.54.63.25516,382
218251.54.64.0/18251.54.64.1 to 251.54.127.254251.54.127.25516,382
219251.54.128.0/18251.54.128.1 to 251.54.191.254251.54.191.25516,382
220251.54.192.0/18251.54.192.1 to 251.54.255.254251.54.255.25516,382
221251.55.0.0/18251.55.0.1 to 251.55.63.254251.55.63.25516,382
222251.55.64.0/18251.55.64.1 to 251.55.127.254251.55.127.25516,382
223251.55.128.0/18251.55.128.1 to 251.55.191.254251.55.191.25516,382
224251.55.192.0/18251.55.192.1 to 251.55.255.254251.55.255.25516,382
225251.56.0.0/18251.56.0.1 to 251.56.63.254251.56.63.25516,382
226251.56.64.0/18251.56.64.1 to 251.56.127.254251.56.127.25516,382
227251.56.128.0/18251.56.128.1 to 251.56.191.254251.56.191.25516,382
228251.56.192.0/18251.56.192.1 to 251.56.255.254251.56.255.25516,382
229251.57.0.0/18251.57.0.1 to 251.57.63.254251.57.63.25516,382
230251.57.64.0/18251.57.64.1 to 251.57.127.254251.57.127.25516,382
231251.57.128.0/18251.57.128.1 to 251.57.191.254251.57.191.25516,382
232251.57.192.0/18251.57.192.1 to 251.57.255.254251.57.255.25516,382
233251.58.0.0/18251.58.0.1 to 251.58.63.254251.58.63.25516,382
234251.58.64.0/18251.58.64.1 to 251.58.127.254251.58.127.25516,382
235251.58.128.0/18251.58.128.1 to 251.58.191.254251.58.191.25516,382
236251.58.192.0/18251.58.192.1 to 251.58.255.254251.58.255.25516,382
237251.59.0.0/18251.59.0.1 to 251.59.63.254251.59.63.25516,382
238251.59.64.0/18251.59.64.1 to 251.59.127.254251.59.127.25516,382
239251.59.128.0/18251.59.128.1 to 251.59.191.254251.59.191.25516,382
240251.59.192.0/18251.59.192.1 to 251.59.255.254251.59.255.25516,382
241251.60.0.0/18251.60.0.1 to 251.60.63.254251.60.63.25516,382
242251.60.64.0/18251.60.64.1 to 251.60.127.254251.60.127.25516,382
243251.60.128.0/18251.60.128.1 to 251.60.191.254251.60.191.25516,382
244251.60.192.0/18251.60.192.1 to 251.60.255.254251.60.255.25516,382
245251.61.0.0/18251.61.0.1 to 251.61.63.254251.61.63.25516,382
246251.61.64.0/18251.61.64.1 to 251.61.127.254251.61.127.25516,382
247251.61.128.0/18251.61.128.1 to 251.61.191.254251.61.191.25516,382
248251.61.192.0/18251.61.192.1 to 251.61.255.254251.61.255.25516,382
249251.62.0.0/18251.62.0.1 to 251.62.63.254251.62.63.25516,382
250251.62.64.0/18251.62.64.1 to 251.62.127.254251.62.127.25516,382
251251.62.128.0/18251.62.128.1 to 251.62.191.254251.62.191.25516,382
252251.62.192.0/18251.62.192.1 to 251.62.255.254251.62.255.25516,382
253251.63.0.0/18251.63.0.1 to 251.63.63.254251.63.63.25516,382
254251.63.64.0/18251.63.64.1 to 251.63.127.254251.63.127.25516,382
255251.63.128.0/18251.63.128.1 to 251.63.191.254251.63.191.25516,382
256251.63.192.0/18251.63.192.1 to 251.63.255.254251.63.255.25516,382

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.