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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.

Network221.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
221.0.0.0
Broadcast address
221.255.255.255
First usable
221.0.0.1
Last usable
221.255.255.254
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 DD000000 · Integer 3707764736 to 3724541951
Reverse DNS zone
221.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11011101..00000000.00000000.00000000221.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network11011101..00000000.00000000.00000000221.0.0.0
Broadcast11011101..11111111.11111111.11111111221.255.255.255
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)

221.0.0.0/8 makes 4,096 subnets of /20; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1221.0.0.0/20221.0.0.1 to 221.0.15.254221.0.15.2554,094
2221.0.16.0/20221.0.16.1 to 221.0.31.254221.0.31.2554,094
3221.0.32.0/20221.0.32.1 to 221.0.47.254221.0.47.2554,094
4221.0.48.0/20221.0.48.1 to 221.0.63.254221.0.63.2554,094
5221.0.64.0/20221.0.64.1 to 221.0.79.254221.0.79.2554,094
6221.0.80.0/20221.0.80.1 to 221.0.95.254221.0.95.2554,094
7221.0.96.0/20221.0.96.1 to 221.0.111.254221.0.111.2554,094
8221.0.112.0/20221.0.112.1 to 221.0.127.254221.0.127.2554,094
9221.0.128.0/20221.0.128.1 to 221.0.143.254221.0.143.2554,094
10221.0.144.0/20221.0.144.1 to 221.0.159.254221.0.159.2554,094
11221.0.160.0/20221.0.160.1 to 221.0.175.254221.0.175.2554,094
12221.0.176.0/20221.0.176.1 to 221.0.191.254221.0.191.2554,094
13221.0.192.0/20221.0.192.1 to 221.0.207.254221.0.207.2554,094
14221.0.208.0/20221.0.208.1 to 221.0.223.254221.0.223.2554,094
15221.0.224.0/20221.0.224.1 to 221.0.239.254221.0.239.2554,094
16221.0.240.0/20221.0.240.1 to 221.0.255.254221.0.255.2554,094
17221.1.0.0/20221.1.0.1 to 221.1.15.254221.1.15.2554,094
18221.1.16.0/20221.1.16.1 to 221.1.31.254221.1.31.2554,094
19221.1.32.0/20221.1.32.1 to 221.1.47.254221.1.47.2554,094
20221.1.48.0/20221.1.48.1 to 221.1.63.254221.1.63.2554,094
21221.1.64.0/20221.1.64.1 to 221.1.79.254221.1.79.2554,094
22221.1.80.0/20221.1.80.1 to 221.1.95.254221.1.95.2554,094
23221.1.96.0/20221.1.96.1 to 221.1.111.254221.1.111.2554,094
24221.1.112.0/20221.1.112.1 to 221.1.127.254221.1.127.2554,094
25221.1.128.0/20221.1.128.1 to 221.1.143.254221.1.143.2554,094
26221.1.144.0/20221.1.144.1 to 221.1.159.254221.1.159.2554,094
27221.1.160.0/20221.1.160.1 to 221.1.175.254221.1.175.2554,094
28221.1.176.0/20221.1.176.1 to 221.1.191.254221.1.191.2554,094
29221.1.192.0/20221.1.192.1 to 221.1.207.254221.1.207.2554,094
30221.1.208.0/20221.1.208.1 to 221.1.223.254221.1.223.2554,094
31221.1.224.0/20221.1.224.1 to 221.1.239.254221.1.239.2554,094
32221.1.240.0/20221.1.240.1 to 221.1.255.254221.1.255.2554,094
33221.2.0.0/20221.2.0.1 to 221.2.15.254221.2.15.2554,094
34221.2.16.0/20221.2.16.1 to 221.2.31.254221.2.31.2554,094
35221.2.32.0/20221.2.32.1 to 221.2.47.254221.2.47.2554,094
36221.2.48.0/20221.2.48.1 to 221.2.63.254221.2.63.2554,094
37221.2.64.0/20221.2.64.1 to 221.2.79.254221.2.79.2554,094
38221.2.80.0/20221.2.80.1 to 221.2.95.254221.2.95.2554,094
39221.2.96.0/20221.2.96.1 to 221.2.111.254221.2.111.2554,094
40221.2.112.0/20221.2.112.1 to 221.2.127.254221.2.127.2554,094
41221.2.128.0/20221.2.128.1 to 221.2.143.254221.2.143.2554,094
42221.2.144.0/20221.2.144.1 to 221.2.159.254221.2.159.2554,094
43221.2.160.0/20221.2.160.1 to 221.2.175.254221.2.175.2554,094
44221.2.176.0/20221.2.176.1 to 221.2.191.254221.2.191.2554,094
45221.2.192.0/20221.2.192.1 to 221.2.207.254221.2.207.2554,094
46221.2.208.0/20221.2.208.1 to 221.2.223.254221.2.223.2554,094
47221.2.224.0/20221.2.224.1 to 221.2.239.254221.2.239.2554,094
48221.2.240.0/20221.2.240.1 to 221.2.255.254221.2.255.2554,094
49221.3.0.0/20221.3.0.1 to 221.3.15.254221.3.15.2554,094
50221.3.16.0/20221.3.16.1 to 221.3.31.254221.3.31.2554,094
51221.3.32.0/20221.3.32.1 to 221.3.47.254221.3.47.2554,094
52221.3.48.0/20221.3.48.1 to 221.3.63.254221.3.63.2554,094
53221.3.64.0/20221.3.64.1 to 221.3.79.254221.3.79.2554,094
54221.3.80.0/20221.3.80.1 to 221.3.95.254221.3.95.2554,094
55221.3.96.0/20221.3.96.1 to 221.3.111.254221.3.111.2554,094
56221.3.112.0/20221.3.112.1 to 221.3.127.254221.3.127.2554,094
57221.3.128.0/20221.3.128.1 to 221.3.143.254221.3.143.2554,094
58221.3.144.0/20221.3.144.1 to 221.3.159.254221.3.159.2554,094
59221.3.160.0/20221.3.160.1 to 221.3.175.254221.3.175.2554,094
60221.3.176.0/20221.3.176.1 to 221.3.191.254221.3.191.2554,094
61221.3.192.0/20221.3.192.1 to 221.3.207.254221.3.207.2554,094
62221.3.208.0/20221.3.208.1 to 221.3.223.254221.3.223.2554,094
63221.3.224.0/20221.3.224.1 to 221.3.239.254221.3.239.2554,094
64221.3.240.0/20221.3.240.1 to 221.3.255.254221.3.255.2554,094
65221.4.0.0/20221.4.0.1 to 221.4.15.254221.4.15.2554,094
66221.4.16.0/20221.4.16.1 to 221.4.31.254221.4.31.2554,094
67221.4.32.0/20221.4.32.1 to 221.4.47.254221.4.47.2554,094
68221.4.48.0/20221.4.48.1 to 221.4.63.254221.4.63.2554,094
69221.4.64.0/20221.4.64.1 to 221.4.79.254221.4.79.2554,094
70221.4.80.0/20221.4.80.1 to 221.4.95.254221.4.95.2554,094
71221.4.96.0/20221.4.96.1 to 221.4.111.254221.4.111.2554,094
72221.4.112.0/20221.4.112.1 to 221.4.127.254221.4.127.2554,094
73221.4.128.0/20221.4.128.1 to 221.4.143.254221.4.143.2554,094
74221.4.144.0/20221.4.144.1 to 221.4.159.254221.4.159.2554,094
75221.4.160.0/20221.4.160.1 to 221.4.175.254221.4.175.2554,094
76221.4.176.0/20221.4.176.1 to 221.4.191.254221.4.191.2554,094
77221.4.192.0/20221.4.192.1 to 221.4.207.254221.4.207.2554,094
78221.4.208.0/20221.4.208.1 to 221.4.223.254221.4.223.2554,094
79221.4.224.0/20221.4.224.1 to 221.4.239.254221.4.239.2554,094
80221.4.240.0/20221.4.240.1 to 221.4.255.254221.4.255.2554,094
81221.5.0.0/20221.5.0.1 to 221.5.15.254221.5.15.2554,094
82221.5.16.0/20221.5.16.1 to 221.5.31.254221.5.31.2554,094
83221.5.32.0/20221.5.32.1 to 221.5.47.254221.5.47.2554,094
84221.5.48.0/20221.5.48.1 to 221.5.63.254221.5.63.2554,094
85221.5.64.0/20221.5.64.1 to 221.5.79.254221.5.79.2554,094
86221.5.80.0/20221.5.80.1 to 221.5.95.254221.5.95.2554,094
87221.5.96.0/20221.5.96.1 to 221.5.111.254221.5.111.2554,094
88221.5.112.0/20221.5.112.1 to 221.5.127.254221.5.127.2554,094
89221.5.128.0/20221.5.128.1 to 221.5.143.254221.5.143.2554,094
90221.5.144.0/20221.5.144.1 to 221.5.159.254221.5.159.2554,094
91221.5.160.0/20221.5.160.1 to 221.5.175.254221.5.175.2554,094
92221.5.176.0/20221.5.176.1 to 221.5.191.254221.5.191.2554,094
93221.5.192.0/20221.5.192.1 to 221.5.207.254221.5.207.2554,094
94221.5.208.0/20221.5.208.1 to 221.5.223.254221.5.223.2554,094
95221.5.224.0/20221.5.224.1 to 221.5.239.254221.5.239.2554,094
96221.5.240.0/20221.5.240.1 to 221.5.255.254221.5.255.2554,094
97221.6.0.0/20221.6.0.1 to 221.6.15.254221.6.15.2554,094
98221.6.16.0/20221.6.16.1 to 221.6.31.254221.6.31.2554,094
99221.6.32.0/20221.6.32.1 to 221.6.47.254221.6.47.2554,094
100221.6.48.0/20221.6.48.1 to 221.6.63.254221.6.63.2554,094
101221.6.64.0/20221.6.64.1 to 221.6.79.254221.6.79.2554,094
102221.6.80.0/20221.6.80.1 to 221.6.95.254221.6.95.2554,094
103221.6.96.0/20221.6.96.1 to 221.6.111.254221.6.111.2554,094
104221.6.112.0/20221.6.112.1 to 221.6.127.254221.6.127.2554,094
105221.6.128.0/20221.6.128.1 to 221.6.143.254221.6.143.2554,094
106221.6.144.0/20221.6.144.1 to 221.6.159.254221.6.159.2554,094
107221.6.160.0/20221.6.160.1 to 221.6.175.254221.6.175.2554,094
108221.6.176.0/20221.6.176.1 to 221.6.191.254221.6.191.2554,094
109221.6.192.0/20221.6.192.1 to 221.6.207.254221.6.207.2554,094
110221.6.208.0/20221.6.208.1 to 221.6.223.254221.6.223.2554,094
111221.6.224.0/20221.6.224.1 to 221.6.239.254221.6.239.2554,094
112221.6.240.0/20221.6.240.1 to 221.6.255.254221.6.255.2554,094
113221.7.0.0/20221.7.0.1 to 221.7.15.254221.7.15.2554,094
114221.7.16.0/20221.7.16.1 to 221.7.31.254221.7.31.2554,094
115221.7.32.0/20221.7.32.1 to 221.7.47.254221.7.47.2554,094
116221.7.48.0/20221.7.48.1 to 221.7.63.254221.7.63.2554,094
117221.7.64.0/20221.7.64.1 to 221.7.79.254221.7.79.2554,094
118221.7.80.0/20221.7.80.1 to 221.7.95.254221.7.95.2554,094
119221.7.96.0/20221.7.96.1 to 221.7.111.254221.7.111.2554,094
120221.7.112.0/20221.7.112.1 to 221.7.127.254221.7.127.2554,094
121221.7.128.0/20221.7.128.1 to 221.7.143.254221.7.143.2554,094
122221.7.144.0/20221.7.144.1 to 221.7.159.254221.7.159.2554,094
123221.7.160.0/20221.7.160.1 to 221.7.175.254221.7.175.2554,094
124221.7.176.0/20221.7.176.1 to 221.7.191.254221.7.191.2554,094
125221.7.192.0/20221.7.192.1 to 221.7.207.254221.7.207.2554,094
126221.7.208.0/20221.7.208.1 to 221.7.223.254221.7.223.2554,094
127221.7.224.0/20221.7.224.1 to 221.7.239.254221.7.239.2554,094
128221.7.240.0/20221.7.240.1 to 221.7.255.254221.7.255.2554,094
129221.8.0.0/20221.8.0.1 to 221.8.15.254221.8.15.2554,094
130221.8.16.0/20221.8.16.1 to 221.8.31.254221.8.31.2554,094
131221.8.32.0/20221.8.32.1 to 221.8.47.254221.8.47.2554,094
132221.8.48.0/20221.8.48.1 to 221.8.63.254221.8.63.2554,094
133221.8.64.0/20221.8.64.1 to 221.8.79.254221.8.79.2554,094
134221.8.80.0/20221.8.80.1 to 221.8.95.254221.8.95.2554,094
135221.8.96.0/20221.8.96.1 to 221.8.111.254221.8.111.2554,094
136221.8.112.0/20221.8.112.1 to 221.8.127.254221.8.127.2554,094
137221.8.128.0/20221.8.128.1 to 221.8.143.254221.8.143.2554,094
138221.8.144.0/20221.8.144.1 to 221.8.159.254221.8.159.2554,094
139221.8.160.0/20221.8.160.1 to 221.8.175.254221.8.175.2554,094
140221.8.176.0/20221.8.176.1 to 221.8.191.254221.8.191.2554,094
141221.8.192.0/20221.8.192.1 to 221.8.207.254221.8.207.2554,094
142221.8.208.0/20221.8.208.1 to 221.8.223.254221.8.223.2554,094
143221.8.224.0/20221.8.224.1 to 221.8.239.254221.8.239.2554,094
144221.8.240.0/20221.8.240.1 to 221.8.255.254221.8.255.2554,094
145221.9.0.0/20221.9.0.1 to 221.9.15.254221.9.15.2554,094
146221.9.16.0/20221.9.16.1 to 221.9.31.254221.9.31.2554,094
147221.9.32.0/20221.9.32.1 to 221.9.47.254221.9.47.2554,094
148221.9.48.0/20221.9.48.1 to 221.9.63.254221.9.63.2554,094
149221.9.64.0/20221.9.64.1 to 221.9.79.254221.9.79.2554,094
150221.9.80.0/20221.9.80.1 to 221.9.95.254221.9.95.2554,094
151221.9.96.0/20221.9.96.1 to 221.9.111.254221.9.111.2554,094
152221.9.112.0/20221.9.112.1 to 221.9.127.254221.9.127.2554,094
153221.9.128.0/20221.9.128.1 to 221.9.143.254221.9.143.2554,094
154221.9.144.0/20221.9.144.1 to 221.9.159.254221.9.159.2554,094
155221.9.160.0/20221.9.160.1 to 221.9.175.254221.9.175.2554,094
156221.9.176.0/20221.9.176.1 to 221.9.191.254221.9.191.2554,094
157221.9.192.0/20221.9.192.1 to 221.9.207.254221.9.207.2554,094
158221.9.208.0/20221.9.208.1 to 221.9.223.254221.9.223.2554,094
159221.9.224.0/20221.9.224.1 to 221.9.239.254221.9.239.2554,094
160221.9.240.0/20221.9.240.1 to 221.9.255.254221.9.255.2554,094
161221.10.0.0/20221.10.0.1 to 221.10.15.254221.10.15.2554,094
162221.10.16.0/20221.10.16.1 to 221.10.31.254221.10.31.2554,094
163221.10.32.0/20221.10.32.1 to 221.10.47.254221.10.47.2554,094
164221.10.48.0/20221.10.48.1 to 221.10.63.254221.10.63.2554,094
165221.10.64.0/20221.10.64.1 to 221.10.79.254221.10.79.2554,094
166221.10.80.0/20221.10.80.1 to 221.10.95.254221.10.95.2554,094
167221.10.96.0/20221.10.96.1 to 221.10.111.254221.10.111.2554,094
168221.10.112.0/20221.10.112.1 to 221.10.127.254221.10.127.2554,094
169221.10.128.0/20221.10.128.1 to 221.10.143.254221.10.143.2554,094
170221.10.144.0/20221.10.144.1 to 221.10.159.254221.10.159.2554,094
171221.10.160.0/20221.10.160.1 to 221.10.175.254221.10.175.2554,094
172221.10.176.0/20221.10.176.1 to 221.10.191.254221.10.191.2554,094
173221.10.192.0/20221.10.192.1 to 221.10.207.254221.10.207.2554,094
174221.10.208.0/20221.10.208.1 to 221.10.223.254221.10.223.2554,094
175221.10.224.0/20221.10.224.1 to 221.10.239.254221.10.239.2554,094
176221.10.240.0/20221.10.240.1 to 221.10.255.254221.10.255.2554,094
177221.11.0.0/20221.11.0.1 to 221.11.15.254221.11.15.2554,094
178221.11.16.0/20221.11.16.1 to 221.11.31.254221.11.31.2554,094
179221.11.32.0/20221.11.32.1 to 221.11.47.254221.11.47.2554,094
180221.11.48.0/20221.11.48.1 to 221.11.63.254221.11.63.2554,094
181221.11.64.0/20221.11.64.1 to 221.11.79.254221.11.79.2554,094
182221.11.80.0/20221.11.80.1 to 221.11.95.254221.11.95.2554,094
183221.11.96.0/20221.11.96.1 to 221.11.111.254221.11.111.2554,094
184221.11.112.0/20221.11.112.1 to 221.11.127.254221.11.127.2554,094
185221.11.128.0/20221.11.128.1 to 221.11.143.254221.11.143.2554,094
186221.11.144.0/20221.11.144.1 to 221.11.159.254221.11.159.2554,094
187221.11.160.0/20221.11.160.1 to 221.11.175.254221.11.175.2554,094
188221.11.176.0/20221.11.176.1 to 221.11.191.254221.11.191.2554,094
189221.11.192.0/20221.11.192.1 to 221.11.207.254221.11.207.2554,094
190221.11.208.0/20221.11.208.1 to 221.11.223.254221.11.223.2554,094
191221.11.224.0/20221.11.224.1 to 221.11.239.254221.11.239.2554,094
192221.11.240.0/20221.11.240.1 to 221.11.255.254221.11.255.2554,094
193221.12.0.0/20221.12.0.1 to 221.12.15.254221.12.15.2554,094
194221.12.16.0/20221.12.16.1 to 221.12.31.254221.12.31.2554,094
195221.12.32.0/20221.12.32.1 to 221.12.47.254221.12.47.2554,094
196221.12.48.0/20221.12.48.1 to 221.12.63.254221.12.63.2554,094
197221.12.64.0/20221.12.64.1 to 221.12.79.254221.12.79.2554,094
198221.12.80.0/20221.12.80.1 to 221.12.95.254221.12.95.2554,094
199221.12.96.0/20221.12.96.1 to 221.12.111.254221.12.111.2554,094
200221.12.112.0/20221.12.112.1 to 221.12.127.254221.12.127.2554,094
201221.12.128.0/20221.12.128.1 to 221.12.143.254221.12.143.2554,094
202221.12.144.0/20221.12.144.1 to 221.12.159.254221.12.159.2554,094
203221.12.160.0/20221.12.160.1 to 221.12.175.254221.12.175.2554,094
204221.12.176.0/20221.12.176.1 to 221.12.191.254221.12.191.2554,094
205221.12.192.0/20221.12.192.1 to 221.12.207.254221.12.207.2554,094
206221.12.208.0/20221.12.208.1 to 221.12.223.254221.12.223.2554,094
207221.12.224.0/20221.12.224.1 to 221.12.239.254221.12.239.2554,094
208221.12.240.0/20221.12.240.1 to 221.12.255.254221.12.255.2554,094
209221.13.0.0/20221.13.0.1 to 221.13.15.254221.13.15.2554,094
210221.13.16.0/20221.13.16.1 to 221.13.31.254221.13.31.2554,094
211221.13.32.0/20221.13.32.1 to 221.13.47.254221.13.47.2554,094
212221.13.48.0/20221.13.48.1 to 221.13.63.254221.13.63.2554,094
213221.13.64.0/20221.13.64.1 to 221.13.79.254221.13.79.2554,094
214221.13.80.0/20221.13.80.1 to 221.13.95.254221.13.95.2554,094
215221.13.96.0/20221.13.96.1 to 221.13.111.254221.13.111.2554,094
216221.13.112.0/20221.13.112.1 to 221.13.127.254221.13.127.2554,094
217221.13.128.0/20221.13.128.1 to 221.13.143.254221.13.143.2554,094
218221.13.144.0/20221.13.144.1 to 221.13.159.254221.13.159.2554,094
219221.13.160.0/20221.13.160.1 to 221.13.175.254221.13.175.2554,094
220221.13.176.0/20221.13.176.1 to 221.13.191.254221.13.191.2554,094
221221.13.192.0/20221.13.192.1 to 221.13.207.254221.13.207.2554,094
222221.13.208.0/20221.13.208.1 to 221.13.223.254221.13.223.2554,094
223221.13.224.0/20221.13.224.1 to 221.13.239.254221.13.239.2554,094
224221.13.240.0/20221.13.240.1 to 221.13.255.254221.13.255.2554,094
225221.14.0.0/20221.14.0.1 to 221.14.15.254221.14.15.2554,094
226221.14.16.0/20221.14.16.1 to 221.14.31.254221.14.31.2554,094
227221.14.32.0/20221.14.32.1 to 221.14.47.254221.14.47.2554,094
228221.14.48.0/20221.14.48.1 to 221.14.63.254221.14.63.2554,094
229221.14.64.0/20221.14.64.1 to 221.14.79.254221.14.79.2554,094
230221.14.80.0/20221.14.80.1 to 221.14.95.254221.14.95.2554,094
231221.14.96.0/20221.14.96.1 to 221.14.111.254221.14.111.2554,094
232221.14.112.0/20221.14.112.1 to 221.14.127.254221.14.127.2554,094
233221.14.128.0/20221.14.128.1 to 221.14.143.254221.14.143.2554,094
234221.14.144.0/20221.14.144.1 to 221.14.159.254221.14.159.2554,094
235221.14.160.0/20221.14.160.1 to 221.14.175.254221.14.175.2554,094
236221.14.176.0/20221.14.176.1 to 221.14.191.254221.14.191.2554,094
237221.14.192.0/20221.14.192.1 to 221.14.207.254221.14.207.2554,094
238221.14.208.0/20221.14.208.1 to 221.14.223.254221.14.223.2554,094
239221.14.224.0/20221.14.224.1 to 221.14.239.254221.14.239.2554,094
240221.14.240.0/20221.14.240.1 to 221.14.255.254221.14.255.2554,094
241221.15.0.0/20221.15.0.1 to 221.15.15.254221.15.15.2554,094
242221.15.16.0/20221.15.16.1 to 221.15.31.254221.15.31.2554,094
243221.15.32.0/20221.15.32.1 to 221.15.47.254221.15.47.2554,094
244221.15.48.0/20221.15.48.1 to 221.15.63.254221.15.63.2554,094
245221.15.64.0/20221.15.64.1 to 221.15.79.254221.15.79.2554,094
246221.15.80.0/20221.15.80.1 to 221.15.95.254221.15.95.2554,094
247221.15.96.0/20221.15.96.1 to 221.15.111.254221.15.111.2554,094
248221.15.112.0/20221.15.112.1 to 221.15.127.254221.15.127.2554,094
249221.15.128.0/20221.15.128.1 to 221.15.143.254221.15.143.2554,094
250221.15.144.0/20221.15.144.1 to 221.15.159.254221.15.159.2554,094
251221.15.160.0/20221.15.160.1 to 221.15.175.254221.15.175.2554,094
252221.15.176.0/20221.15.176.1 to 221.15.191.254221.15.191.2554,094
253221.15.192.0/20221.15.192.1 to 221.15.207.254221.15.207.2554,094
254221.15.208.0/20221.15.208.1 to 221.15.223.254221.15.223.2554,094
255221.15.224.0/20221.15.224.1 to 221.15.239.254221.15.239.2554,094
256221.15.240.0/20221.15.240.1 to 221.15.255.254221.15.255.2554,094

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.