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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/16
/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 256 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1251.0.0.0/16251.0.0.1 to 251.0.255.254251.0.255.25565,534
2251.1.0.0/16251.1.0.1 to 251.1.255.254251.1.255.25565,534
3251.2.0.0/16251.2.0.1 to 251.2.255.254251.2.255.25565,534
4251.3.0.0/16251.3.0.1 to 251.3.255.254251.3.255.25565,534
5251.4.0.0/16251.4.0.1 to 251.4.255.254251.4.255.25565,534
6251.5.0.0/16251.5.0.1 to 251.5.255.254251.5.255.25565,534
7251.6.0.0/16251.6.0.1 to 251.6.255.254251.6.255.25565,534
8251.7.0.0/16251.7.0.1 to 251.7.255.254251.7.255.25565,534
9251.8.0.0/16251.8.0.1 to 251.8.255.254251.8.255.25565,534
10251.9.0.0/16251.9.0.1 to 251.9.255.254251.9.255.25565,534
11251.10.0.0/16251.10.0.1 to 251.10.255.254251.10.255.25565,534
12251.11.0.0/16251.11.0.1 to 251.11.255.254251.11.255.25565,534
13251.12.0.0/16251.12.0.1 to 251.12.255.254251.12.255.25565,534
14251.13.0.0/16251.13.0.1 to 251.13.255.254251.13.255.25565,534
15251.14.0.0/16251.14.0.1 to 251.14.255.254251.14.255.25565,534
16251.15.0.0/16251.15.0.1 to 251.15.255.254251.15.255.25565,534
17251.16.0.0/16251.16.0.1 to 251.16.255.254251.16.255.25565,534
18251.17.0.0/16251.17.0.1 to 251.17.255.254251.17.255.25565,534
19251.18.0.0/16251.18.0.1 to 251.18.255.254251.18.255.25565,534
20251.19.0.0/16251.19.0.1 to 251.19.255.254251.19.255.25565,534
21251.20.0.0/16251.20.0.1 to 251.20.255.254251.20.255.25565,534
22251.21.0.0/16251.21.0.1 to 251.21.255.254251.21.255.25565,534
23251.22.0.0/16251.22.0.1 to 251.22.255.254251.22.255.25565,534
24251.23.0.0/16251.23.0.1 to 251.23.255.254251.23.255.25565,534
25251.24.0.0/16251.24.0.1 to 251.24.255.254251.24.255.25565,534
26251.25.0.0/16251.25.0.1 to 251.25.255.254251.25.255.25565,534
27251.26.0.0/16251.26.0.1 to 251.26.255.254251.26.255.25565,534
28251.27.0.0/16251.27.0.1 to 251.27.255.254251.27.255.25565,534
29251.28.0.0/16251.28.0.1 to 251.28.255.254251.28.255.25565,534
30251.29.0.0/16251.29.0.1 to 251.29.255.254251.29.255.25565,534
31251.30.0.0/16251.30.0.1 to 251.30.255.254251.30.255.25565,534
32251.31.0.0/16251.31.0.1 to 251.31.255.254251.31.255.25565,534
33251.32.0.0/16251.32.0.1 to 251.32.255.254251.32.255.25565,534
34251.33.0.0/16251.33.0.1 to 251.33.255.254251.33.255.25565,534
35251.34.0.0/16251.34.0.1 to 251.34.255.254251.34.255.25565,534
36251.35.0.0/16251.35.0.1 to 251.35.255.254251.35.255.25565,534
37251.36.0.0/16251.36.0.1 to 251.36.255.254251.36.255.25565,534
38251.37.0.0/16251.37.0.1 to 251.37.255.254251.37.255.25565,534
39251.38.0.0/16251.38.0.1 to 251.38.255.254251.38.255.25565,534
40251.39.0.0/16251.39.0.1 to 251.39.255.254251.39.255.25565,534
41251.40.0.0/16251.40.0.1 to 251.40.255.254251.40.255.25565,534
42251.41.0.0/16251.41.0.1 to 251.41.255.254251.41.255.25565,534
43251.42.0.0/16251.42.0.1 to 251.42.255.254251.42.255.25565,534
44251.43.0.0/16251.43.0.1 to 251.43.255.254251.43.255.25565,534
45251.44.0.0/16251.44.0.1 to 251.44.255.254251.44.255.25565,534
46251.45.0.0/16251.45.0.1 to 251.45.255.254251.45.255.25565,534
47251.46.0.0/16251.46.0.1 to 251.46.255.254251.46.255.25565,534
48251.47.0.0/16251.47.0.1 to 251.47.255.254251.47.255.25565,534
49251.48.0.0/16251.48.0.1 to 251.48.255.254251.48.255.25565,534
50251.49.0.0/16251.49.0.1 to 251.49.255.254251.49.255.25565,534
51251.50.0.0/16251.50.0.1 to 251.50.255.254251.50.255.25565,534
52251.51.0.0/16251.51.0.1 to 251.51.255.254251.51.255.25565,534
53251.52.0.0/16251.52.0.1 to 251.52.255.254251.52.255.25565,534
54251.53.0.0/16251.53.0.1 to 251.53.255.254251.53.255.25565,534
55251.54.0.0/16251.54.0.1 to 251.54.255.254251.54.255.25565,534
56251.55.0.0/16251.55.0.1 to 251.55.255.254251.55.255.25565,534
57251.56.0.0/16251.56.0.1 to 251.56.255.254251.56.255.25565,534
58251.57.0.0/16251.57.0.1 to 251.57.255.254251.57.255.25565,534
59251.58.0.0/16251.58.0.1 to 251.58.255.254251.58.255.25565,534
60251.59.0.0/16251.59.0.1 to 251.59.255.254251.59.255.25565,534
61251.60.0.0/16251.60.0.1 to 251.60.255.254251.60.255.25565,534
62251.61.0.0/16251.61.0.1 to 251.61.255.254251.61.255.25565,534
63251.62.0.0/16251.62.0.1 to 251.62.255.254251.62.255.25565,534
64251.63.0.0/16251.63.0.1 to 251.63.255.254251.63.255.25565,534
65251.64.0.0/16251.64.0.1 to 251.64.255.254251.64.255.25565,534
66251.65.0.0/16251.65.0.1 to 251.65.255.254251.65.255.25565,534
67251.66.0.0/16251.66.0.1 to 251.66.255.254251.66.255.25565,534
68251.67.0.0/16251.67.0.1 to 251.67.255.254251.67.255.25565,534
69251.68.0.0/16251.68.0.1 to 251.68.255.254251.68.255.25565,534
70251.69.0.0/16251.69.0.1 to 251.69.255.254251.69.255.25565,534
71251.70.0.0/16251.70.0.1 to 251.70.255.254251.70.255.25565,534
72251.71.0.0/16251.71.0.1 to 251.71.255.254251.71.255.25565,534
73251.72.0.0/16251.72.0.1 to 251.72.255.254251.72.255.25565,534
74251.73.0.0/16251.73.0.1 to 251.73.255.254251.73.255.25565,534
75251.74.0.0/16251.74.0.1 to 251.74.255.254251.74.255.25565,534
76251.75.0.0/16251.75.0.1 to 251.75.255.254251.75.255.25565,534
77251.76.0.0/16251.76.0.1 to 251.76.255.254251.76.255.25565,534
78251.77.0.0/16251.77.0.1 to 251.77.255.254251.77.255.25565,534
79251.78.0.0/16251.78.0.1 to 251.78.255.254251.78.255.25565,534
80251.79.0.0/16251.79.0.1 to 251.79.255.254251.79.255.25565,534
81251.80.0.0/16251.80.0.1 to 251.80.255.254251.80.255.25565,534
82251.81.0.0/16251.81.0.1 to 251.81.255.254251.81.255.25565,534
83251.82.0.0/16251.82.0.1 to 251.82.255.254251.82.255.25565,534
84251.83.0.0/16251.83.0.1 to 251.83.255.254251.83.255.25565,534
85251.84.0.0/16251.84.0.1 to 251.84.255.254251.84.255.25565,534
86251.85.0.0/16251.85.0.1 to 251.85.255.254251.85.255.25565,534
87251.86.0.0/16251.86.0.1 to 251.86.255.254251.86.255.25565,534
88251.87.0.0/16251.87.0.1 to 251.87.255.254251.87.255.25565,534
89251.88.0.0/16251.88.0.1 to 251.88.255.254251.88.255.25565,534
90251.89.0.0/16251.89.0.1 to 251.89.255.254251.89.255.25565,534
91251.90.0.0/16251.90.0.1 to 251.90.255.254251.90.255.25565,534
92251.91.0.0/16251.91.0.1 to 251.91.255.254251.91.255.25565,534
93251.92.0.0/16251.92.0.1 to 251.92.255.254251.92.255.25565,534
94251.93.0.0/16251.93.0.1 to 251.93.255.254251.93.255.25565,534
95251.94.0.0/16251.94.0.1 to 251.94.255.254251.94.255.25565,534
96251.95.0.0/16251.95.0.1 to 251.95.255.254251.95.255.25565,534
97251.96.0.0/16251.96.0.1 to 251.96.255.254251.96.255.25565,534
98251.97.0.0/16251.97.0.1 to 251.97.255.254251.97.255.25565,534
99251.98.0.0/16251.98.0.1 to 251.98.255.254251.98.255.25565,534
100251.99.0.0/16251.99.0.1 to 251.99.255.254251.99.255.25565,534
101251.100.0.0/16251.100.0.1 to 251.100.255.254251.100.255.25565,534
102251.101.0.0/16251.101.0.1 to 251.101.255.254251.101.255.25565,534
103251.102.0.0/16251.102.0.1 to 251.102.255.254251.102.255.25565,534
104251.103.0.0/16251.103.0.1 to 251.103.255.254251.103.255.25565,534
105251.104.0.0/16251.104.0.1 to 251.104.255.254251.104.255.25565,534
106251.105.0.0/16251.105.0.1 to 251.105.255.254251.105.255.25565,534
107251.106.0.0/16251.106.0.1 to 251.106.255.254251.106.255.25565,534
108251.107.0.0/16251.107.0.1 to 251.107.255.254251.107.255.25565,534
109251.108.0.0/16251.108.0.1 to 251.108.255.254251.108.255.25565,534
110251.109.0.0/16251.109.0.1 to 251.109.255.254251.109.255.25565,534
111251.110.0.0/16251.110.0.1 to 251.110.255.254251.110.255.25565,534
112251.111.0.0/16251.111.0.1 to 251.111.255.254251.111.255.25565,534
113251.112.0.0/16251.112.0.1 to 251.112.255.254251.112.255.25565,534
114251.113.0.0/16251.113.0.1 to 251.113.255.254251.113.255.25565,534
115251.114.0.0/16251.114.0.1 to 251.114.255.254251.114.255.25565,534
116251.115.0.0/16251.115.0.1 to 251.115.255.254251.115.255.25565,534
117251.116.0.0/16251.116.0.1 to 251.116.255.254251.116.255.25565,534
118251.117.0.0/16251.117.0.1 to 251.117.255.254251.117.255.25565,534
119251.118.0.0/16251.118.0.1 to 251.118.255.254251.118.255.25565,534
120251.119.0.0/16251.119.0.1 to 251.119.255.254251.119.255.25565,534
121251.120.0.0/16251.120.0.1 to 251.120.255.254251.120.255.25565,534
122251.121.0.0/16251.121.0.1 to 251.121.255.254251.121.255.25565,534
123251.122.0.0/16251.122.0.1 to 251.122.255.254251.122.255.25565,534
124251.123.0.0/16251.123.0.1 to 251.123.255.254251.123.255.25565,534
125251.124.0.0/16251.124.0.1 to 251.124.255.254251.124.255.25565,534
126251.125.0.0/16251.125.0.1 to 251.125.255.254251.125.255.25565,534
127251.126.0.0/16251.126.0.1 to 251.126.255.254251.126.255.25565,534
128251.127.0.0/16251.127.0.1 to 251.127.255.254251.127.255.25565,534
129251.128.0.0/16251.128.0.1 to 251.128.255.254251.128.255.25565,534
130251.129.0.0/16251.129.0.1 to 251.129.255.254251.129.255.25565,534
131251.130.0.0/16251.130.0.1 to 251.130.255.254251.130.255.25565,534
132251.131.0.0/16251.131.0.1 to 251.131.255.254251.131.255.25565,534
133251.132.0.0/16251.132.0.1 to 251.132.255.254251.132.255.25565,534
134251.133.0.0/16251.133.0.1 to 251.133.255.254251.133.255.25565,534
135251.134.0.0/16251.134.0.1 to 251.134.255.254251.134.255.25565,534
136251.135.0.0/16251.135.0.1 to 251.135.255.254251.135.255.25565,534
137251.136.0.0/16251.136.0.1 to 251.136.255.254251.136.255.25565,534
138251.137.0.0/16251.137.0.1 to 251.137.255.254251.137.255.25565,534
139251.138.0.0/16251.138.0.1 to 251.138.255.254251.138.255.25565,534
140251.139.0.0/16251.139.0.1 to 251.139.255.254251.139.255.25565,534
141251.140.0.0/16251.140.0.1 to 251.140.255.254251.140.255.25565,534
142251.141.0.0/16251.141.0.1 to 251.141.255.254251.141.255.25565,534
143251.142.0.0/16251.142.0.1 to 251.142.255.254251.142.255.25565,534
144251.143.0.0/16251.143.0.1 to 251.143.255.254251.143.255.25565,534
145251.144.0.0/16251.144.0.1 to 251.144.255.254251.144.255.25565,534
146251.145.0.0/16251.145.0.1 to 251.145.255.254251.145.255.25565,534
147251.146.0.0/16251.146.0.1 to 251.146.255.254251.146.255.25565,534
148251.147.0.0/16251.147.0.1 to 251.147.255.254251.147.255.25565,534
149251.148.0.0/16251.148.0.1 to 251.148.255.254251.148.255.25565,534
150251.149.0.0/16251.149.0.1 to 251.149.255.254251.149.255.25565,534
151251.150.0.0/16251.150.0.1 to 251.150.255.254251.150.255.25565,534
152251.151.0.0/16251.151.0.1 to 251.151.255.254251.151.255.25565,534
153251.152.0.0/16251.152.0.1 to 251.152.255.254251.152.255.25565,534
154251.153.0.0/16251.153.0.1 to 251.153.255.254251.153.255.25565,534
155251.154.0.0/16251.154.0.1 to 251.154.255.254251.154.255.25565,534
156251.155.0.0/16251.155.0.1 to 251.155.255.254251.155.255.25565,534
157251.156.0.0/16251.156.0.1 to 251.156.255.254251.156.255.25565,534
158251.157.0.0/16251.157.0.1 to 251.157.255.254251.157.255.25565,534
159251.158.0.0/16251.158.0.1 to 251.158.255.254251.158.255.25565,534
160251.159.0.0/16251.159.0.1 to 251.159.255.254251.159.255.25565,534
161251.160.0.0/16251.160.0.1 to 251.160.255.254251.160.255.25565,534
162251.161.0.0/16251.161.0.1 to 251.161.255.254251.161.255.25565,534
163251.162.0.0/16251.162.0.1 to 251.162.255.254251.162.255.25565,534
164251.163.0.0/16251.163.0.1 to 251.163.255.254251.163.255.25565,534
165251.164.0.0/16251.164.0.1 to 251.164.255.254251.164.255.25565,534
166251.165.0.0/16251.165.0.1 to 251.165.255.254251.165.255.25565,534
167251.166.0.0/16251.166.0.1 to 251.166.255.254251.166.255.25565,534
168251.167.0.0/16251.167.0.1 to 251.167.255.254251.167.255.25565,534
169251.168.0.0/16251.168.0.1 to 251.168.255.254251.168.255.25565,534
170251.169.0.0/16251.169.0.1 to 251.169.255.254251.169.255.25565,534
171251.170.0.0/16251.170.0.1 to 251.170.255.254251.170.255.25565,534
172251.171.0.0/16251.171.0.1 to 251.171.255.254251.171.255.25565,534
173251.172.0.0/16251.172.0.1 to 251.172.255.254251.172.255.25565,534
174251.173.0.0/16251.173.0.1 to 251.173.255.254251.173.255.25565,534
175251.174.0.0/16251.174.0.1 to 251.174.255.254251.174.255.25565,534
176251.175.0.0/16251.175.0.1 to 251.175.255.254251.175.255.25565,534
177251.176.0.0/16251.176.0.1 to 251.176.255.254251.176.255.25565,534
178251.177.0.0/16251.177.0.1 to 251.177.255.254251.177.255.25565,534
179251.178.0.0/16251.178.0.1 to 251.178.255.254251.178.255.25565,534
180251.179.0.0/16251.179.0.1 to 251.179.255.254251.179.255.25565,534
181251.180.0.0/16251.180.0.1 to 251.180.255.254251.180.255.25565,534
182251.181.0.0/16251.181.0.1 to 251.181.255.254251.181.255.25565,534
183251.182.0.0/16251.182.0.1 to 251.182.255.254251.182.255.25565,534
184251.183.0.0/16251.183.0.1 to 251.183.255.254251.183.255.25565,534
185251.184.0.0/16251.184.0.1 to 251.184.255.254251.184.255.25565,534
186251.185.0.0/16251.185.0.1 to 251.185.255.254251.185.255.25565,534
187251.186.0.0/16251.186.0.1 to 251.186.255.254251.186.255.25565,534
188251.187.0.0/16251.187.0.1 to 251.187.255.254251.187.255.25565,534
189251.188.0.0/16251.188.0.1 to 251.188.255.254251.188.255.25565,534
190251.189.0.0/16251.189.0.1 to 251.189.255.254251.189.255.25565,534
191251.190.0.0/16251.190.0.1 to 251.190.255.254251.190.255.25565,534
192251.191.0.0/16251.191.0.1 to 251.191.255.254251.191.255.25565,534
193251.192.0.0/16251.192.0.1 to 251.192.255.254251.192.255.25565,534
194251.193.0.0/16251.193.0.1 to 251.193.255.254251.193.255.25565,534
195251.194.0.0/16251.194.0.1 to 251.194.255.254251.194.255.25565,534
196251.195.0.0/16251.195.0.1 to 251.195.255.254251.195.255.25565,534
197251.196.0.0/16251.196.0.1 to 251.196.255.254251.196.255.25565,534
198251.197.0.0/16251.197.0.1 to 251.197.255.254251.197.255.25565,534
199251.198.0.0/16251.198.0.1 to 251.198.255.254251.198.255.25565,534
200251.199.0.0/16251.199.0.1 to 251.199.255.254251.199.255.25565,534
201251.200.0.0/16251.200.0.1 to 251.200.255.254251.200.255.25565,534
202251.201.0.0/16251.201.0.1 to 251.201.255.254251.201.255.25565,534
203251.202.0.0/16251.202.0.1 to 251.202.255.254251.202.255.25565,534
204251.203.0.0/16251.203.0.1 to 251.203.255.254251.203.255.25565,534
205251.204.0.0/16251.204.0.1 to 251.204.255.254251.204.255.25565,534
206251.205.0.0/16251.205.0.1 to 251.205.255.254251.205.255.25565,534
207251.206.0.0/16251.206.0.1 to 251.206.255.254251.206.255.25565,534
208251.207.0.0/16251.207.0.1 to 251.207.255.254251.207.255.25565,534
209251.208.0.0/16251.208.0.1 to 251.208.255.254251.208.255.25565,534
210251.209.0.0/16251.209.0.1 to 251.209.255.254251.209.255.25565,534
211251.210.0.0/16251.210.0.1 to 251.210.255.254251.210.255.25565,534
212251.211.0.0/16251.211.0.1 to 251.211.255.254251.211.255.25565,534
213251.212.0.0/16251.212.0.1 to 251.212.255.254251.212.255.25565,534
214251.213.0.0/16251.213.0.1 to 251.213.255.254251.213.255.25565,534
215251.214.0.0/16251.214.0.1 to 251.214.255.254251.214.255.25565,534
216251.215.0.0/16251.215.0.1 to 251.215.255.254251.215.255.25565,534
217251.216.0.0/16251.216.0.1 to 251.216.255.254251.216.255.25565,534
218251.217.0.0/16251.217.0.1 to 251.217.255.254251.217.255.25565,534
219251.218.0.0/16251.218.0.1 to 251.218.255.254251.218.255.25565,534
220251.219.0.0/16251.219.0.1 to 251.219.255.254251.219.255.25565,534
221251.220.0.0/16251.220.0.1 to 251.220.255.254251.220.255.25565,534
222251.221.0.0/16251.221.0.1 to 251.221.255.254251.221.255.25565,534
223251.222.0.0/16251.222.0.1 to 251.222.255.254251.222.255.25565,534
224251.223.0.0/16251.223.0.1 to 251.223.255.254251.223.255.25565,534
225251.224.0.0/16251.224.0.1 to 251.224.255.254251.224.255.25565,534
226251.225.0.0/16251.225.0.1 to 251.225.255.254251.225.255.25565,534
227251.226.0.0/16251.226.0.1 to 251.226.255.254251.226.255.25565,534
228251.227.0.0/16251.227.0.1 to 251.227.255.254251.227.255.25565,534
229251.228.0.0/16251.228.0.1 to 251.228.255.254251.228.255.25565,534
230251.229.0.0/16251.229.0.1 to 251.229.255.254251.229.255.25565,534
231251.230.0.0/16251.230.0.1 to 251.230.255.254251.230.255.25565,534
232251.231.0.0/16251.231.0.1 to 251.231.255.254251.231.255.25565,534
233251.232.0.0/16251.232.0.1 to 251.232.255.254251.232.255.25565,534
234251.233.0.0/16251.233.0.1 to 251.233.255.254251.233.255.25565,534
235251.234.0.0/16251.234.0.1 to 251.234.255.254251.234.255.25565,534
236251.235.0.0/16251.235.0.1 to 251.235.255.254251.235.255.25565,534
237251.236.0.0/16251.236.0.1 to 251.236.255.254251.236.255.25565,534
238251.237.0.0/16251.237.0.1 to 251.237.255.254251.237.255.25565,534
239251.238.0.0/16251.238.0.1 to 251.238.255.254251.238.255.25565,534
240251.239.0.0/16251.239.0.1 to 251.239.255.254251.239.255.25565,534
241251.240.0.0/16251.240.0.1 to 251.240.255.254251.240.255.25565,534
242251.241.0.0/16251.241.0.1 to 251.241.255.254251.241.255.25565,534
243251.242.0.0/16251.242.0.1 to 251.242.255.254251.242.255.25565,534
244251.243.0.0/16251.243.0.1 to 251.243.255.254251.243.255.25565,534
245251.244.0.0/16251.244.0.1 to 251.244.255.254251.244.255.25565,534
246251.245.0.0/16251.245.0.1 to 251.245.255.254251.245.255.25565,534
247251.246.0.0/16251.246.0.1 to 251.246.255.254251.246.255.25565,534
248251.247.0.0/16251.247.0.1 to 251.247.255.254251.247.255.25565,534
249251.248.0.0/16251.248.0.1 to 251.248.255.254251.248.255.25565,534
250251.249.0.0/16251.249.0.1 to 251.249.255.254251.249.255.25565,534
251251.250.0.0/16251.250.0.1 to 251.250.255.254251.250.255.25565,534
252251.251.0.0/16251.251.0.1 to 251.251.255.254251.251.255.25565,534
253251.252.0.0/16251.252.0.1 to 251.252.255.254251.252.255.25565,534
254251.253.0.0/16251.253.0.1 to 251.253.255.254251.253.255.25565,534
255251.254.0.0/16251.254.0.1 to 251.254.255.254251.254.255.25565,534
256251.255.0.0/16251.255.0.1 to 251.255.255.254251.255.255.25565,534

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.