IPv4 Subnet Calculator

Enter an IP with a CIDR prefix or a subnet mask to see its network, broadcast, host range, and host count. You can also split the network into smaller subnets.

Try:192.168.1.10/24 10.0.0.0/8 172.16.5.4/20 203.0.113.9/29

IPv6 calculator →

private IP (RFC 1918)10.0.21.0/24

network10.0.21.0/24

broadcast10.0.21.255

first host10.0.21.1

last host10.0.21.254

subnet mask255.255.255.0

wildcard0.0.0.255

addresses256

usable hosts254

classA

ipcalc 10.0.21.0/24

address00001010.00000000.00010101.00000000

subnet mask11111111.11111111.11111111.00000000

network00001010.00000000.00010101.00000000

broadcast00001010.00000000.00010101.11111111

green = network part, grey = host part

hex0x0a001500

decimal167777536

reverse dns0.21.0.10.in-addr.arpa

ipv4-mapped::ffff:a00:1500

/24 split into /31 · 128 subnets

close ×

#	network	host range	broadcast
1	10.0.21.0/31	10.0.21.0 – 10.0.21.1	10.0.21.1
2	10.0.21.2/31	10.0.21.2 – 10.0.21.3	10.0.21.3
3	10.0.21.4/31	10.0.21.4 – 10.0.21.5	10.0.21.5
4	10.0.21.6/31	10.0.21.6 – 10.0.21.7	10.0.21.7
5	10.0.21.8/31	10.0.21.8 – 10.0.21.9	10.0.21.9
6	10.0.21.10/31	10.0.21.10 – 10.0.21.11	10.0.21.11
7	10.0.21.12/31	10.0.21.12 – 10.0.21.13	10.0.21.13
8	10.0.21.14/31	10.0.21.14 – 10.0.21.15	10.0.21.15
9	10.0.21.16/31	10.0.21.16 – 10.0.21.17	10.0.21.17
10	10.0.21.18/31	10.0.21.18 – 10.0.21.19	10.0.21.19
11	10.0.21.20/31	10.0.21.20 – 10.0.21.21	10.0.21.21
12	10.0.21.22/31	10.0.21.22 – 10.0.21.23	10.0.21.23
13	10.0.21.24/31	10.0.21.24 – 10.0.21.25	10.0.21.25
14	10.0.21.26/31	10.0.21.26 – 10.0.21.27	10.0.21.27
15	10.0.21.28/31	10.0.21.28 – 10.0.21.29	10.0.21.29
16	10.0.21.30/31	10.0.21.30 – 10.0.21.31	10.0.21.31
17	10.0.21.32/31	10.0.21.32 – 10.0.21.33	10.0.21.33
18	10.0.21.34/31	10.0.21.34 – 10.0.21.35	10.0.21.35
19	10.0.21.36/31	10.0.21.36 – 10.0.21.37	10.0.21.37
20	10.0.21.38/31	10.0.21.38 – 10.0.21.39	10.0.21.39
21	10.0.21.40/31	10.0.21.40 – 10.0.21.41	10.0.21.41
22	10.0.21.42/31	10.0.21.42 – 10.0.21.43	10.0.21.43
23	10.0.21.44/31	10.0.21.44 – 10.0.21.45	10.0.21.45
24	10.0.21.46/31	10.0.21.46 – 10.0.21.47	10.0.21.47
25	10.0.21.48/31	10.0.21.48 – 10.0.21.49	10.0.21.49
26	10.0.21.50/31	10.0.21.50 – 10.0.21.51	10.0.21.51
27	10.0.21.52/31	10.0.21.52 – 10.0.21.53	10.0.21.53
28	10.0.21.54/31	10.0.21.54 – 10.0.21.55	10.0.21.55
29	10.0.21.56/31	10.0.21.56 – 10.0.21.57	10.0.21.57
30	10.0.21.58/31	10.0.21.58 – 10.0.21.59	10.0.21.59
31	10.0.21.60/31	10.0.21.60 – 10.0.21.61	10.0.21.61
32	10.0.21.62/31	10.0.21.62 – 10.0.21.63	10.0.21.63
33	10.0.21.64/31	10.0.21.64 – 10.0.21.65	10.0.21.65
34	10.0.21.66/31	10.0.21.66 – 10.0.21.67	10.0.21.67
35	10.0.21.68/31	10.0.21.68 – 10.0.21.69	10.0.21.69
36	10.0.21.70/31	10.0.21.70 – 10.0.21.71	10.0.21.71
37	10.0.21.72/31	10.0.21.72 – 10.0.21.73	10.0.21.73
38	10.0.21.74/31	10.0.21.74 – 10.0.21.75	10.0.21.75
39	10.0.21.76/31	10.0.21.76 – 10.0.21.77	10.0.21.77
40	10.0.21.78/31	10.0.21.78 – 10.0.21.79	10.0.21.79
41	10.0.21.80/31	10.0.21.80 – 10.0.21.81	10.0.21.81
42	10.0.21.82/31	10.0.21.82 – 10.0.21.83	10.0.21.83
43	10.0.21.84/31	10.0.21.84 – 10.0.21.85	10.0.21.85
44	10.0.21.86/31	10.0.21.86 – 10.0.21.87	10.0.21.87
45	10.0.21.88/31	10.0.21.88 – 10.0.21.89	10.0.21.89
46	10.0.21.90/31	10.0.21.90 – 10.0.21.91	10.0.21.91
47	10.0.21.92/31	10.0.21.92 – 10.0.21.93	10.0.21.93
48	10.0.21.94/31	10.0.21.94 – 10.0.21.95	10.0.21.95
49	10.0.21.96/31	10.0.21.96 – 10.0.21.97	10.0.21.97
50	10.0.21.98/31	10.0.21.98 – 10.0.21.99	10.0.21.99
51	10.0.21.100/31	10.0.21.100 – 10.0.21.101	10.0.21.101
52	10.0.21.102/31	10.0.21.102 – 10.0.21.103	10.0.21.103
53	10.0.21.104/31	10.0.21.104 – 10.0.21.105	10.0.21.105
54	10.0.21.106/31	10.0.21.106 – 10.0.21.107	10.0.21.107
55	10.0.21.108/31	10.0.21.108 – 10.0.21.109	10.0.21.109
56	10.0.21.110/31	10.0.21.110 – 10.0.21.111	10.0.21.111
57	10.0.21.112/31	10.0.21.112 – 10.0.21.113	10.0.21.113
58	10.0.21.114/31	10.0.21.114 – 10.0.21.115	10.0.21.115
59	10.0.21.116/31	10.0.21.116 – 10.0.21.117	10.0.21.117
60	10.0.21.118/31	10.0.21.118 – 10.0.21.119	10.0.21.119
61	10.0.21.120/31	10.0.21.120 – 10.0.21.121	10.0.21.121
62	10.0.21.122/31	10.0.21.122 – 10.0.21.123	10.0.21.123
63	10.0.21.124/31	10.0.21.124 – 10.0.21.125	10.0.21.125
64	10.0.21.126/31	10.0.21.126 – 10.0.21.127	10.0.21.127
65	10.0.21.128/31	10.0.21.128 – 10.0.21.129	10.0.21.129
66	10.0.21.130/31	10.0.21.130 – 10.0.21.131	10.0.21.131
67	10.0.21.132/31	10.0.21.132 – 10.0.21.133	10.0.21.133
68	10.0.21.134/31	10.0.21.134 – 10.0.21.135	10.0.21.135
69	10.0.21.136/31	10.0.21.136 – 10.0.21.137	10.0.21.137
70	10.0.21.138/31	10.0.21.138 – 10.0.21.139	10.0.21.139
71	10.0.21.140/31	10.0.21.140 – 10.0.21.141	10.0.21.141
72	10.0.21.142/31	10.0.21.142 – 10.0.21.143	10.0.21.143
73	10.0.21.144/31	10.0.21.144 – 10.0.21.145	10.0.21.145
74	10.0.21.146/31	10.0.21.146 – 10.0.21.147	10.0.21.147
75	10.0.21.148/31	10.0.21.148 – 10.0.21.149	10.0.21.149
76	10.0.21.150/31	10.0.21.150 – 10.0.21.151	10.0.21.151
77	10.0.21.152/31	10.0.21.152 – 10.0.21.153	10.0.21.153
78	10.0.21.154/31	10.0.21.154 – 10.0.21.155	10.0.21.155
79	10.0.21.156/31	10.0.21.156 – 10.0.21.157	10.0.21.157
80	10.0.21.158/31	10.0.21.158 – 10.0.21.159	10.0.21.159
81	10.0.21.160/31	10.0.21.160 – 10.0.21.161	10.0.21.161
82	10.0.21.162/31	10.0.21.162 – 10.0.21.163	10.0.21.163
83	10.0.21.164/31	10.0.21.164 – 10.0.21.165	10.0.21.165
84	10.0.21.166/31	10.0.21.166 – 10.0.21.167	10.0.21.167
85	10.0.21.168/31	10.0.21.168 – 10.0.21.169	10.0.21.169
86	10.0.21.170/31	10.0.21.170 – 10.0.21.171	10.0.21.171
87	10.0.21.172/31	10.0.21.172 – 10.0.21.173	10.0.21.173
88	10.0.21.174/31	10.0.21.174 – 10.0.21.175	10.0.21.175
89	10.0.21.176/31	10.0.21.176 – 10.0.21.177	10.0.21.177
90	10.0.21.178/31	10.0.21.178 – 10.0.21.179	10.0.21.179
91	10.0.21.180/31	10.0.21.180 – 10.0.21.181	10.0.21.181
92	10.0.21.182/31	10.0.21.182 – 10.0.21.183	10.0.21.183
93	10.0.21.184/31	10.0.21.184 – 10.0.21.185	10.0.21.185
94	10.0.21.186/31	10.0.21.186 – 10.0.21.187	10.0.21.187
95	10.0.21.188/31	10.0.21.188 – 10.0.21.189	10.0.21.189
96	10.0.21.190/31	10.0.21.190 – 10.0.21.191	10.0.21.191
97	10.0.21.192/31	10.0.21.192 – 10.0.21.193	10.0.21.193
98	10.0.21.194/31	10.0.21.194 – 10.0.21.195	10.0.21.195
99	10.0.21.196/31	10.0.21.196 – 10.0.21.197	10.0.21.197
100	10.0.21.198/31	10.0.21.198 – 10.0.21.199	10.0.21.199
101	10.0.21.200/31	10.0.21.200 – 10.0.21.201	10.0.21.201
102	10.0.21.202/31	10.0.21.202 – 10.0.21.203	10.0.21.203
103	10.0.21.204/31	10.0.21.204 – 10.0.21.205	10.0.21.205
104	10.0.21.206/31	10.0.21.206 – 10.0.21.207	10.0.21.207
105	10.0.21.208/31	10.0.21.208 – 10.0.21.209	10.0.21.209
106	10.0.21.210/31	10.0.21.210 – 10.0.21.211	10.0.21.211
107	10.0.21.212/31	10.0.21.212 – 10.0.21.213	10.0.21.213
108	10.0.21.214/31	10.0.21.214 – 10.0.21.215	10.0.21.215
109	10.0.21.216/31	10.0.21.216 – 10.0.21.217	10.0.21.217
110	10.0.21.218/31	10.0.21.218 – 10.0.21.219	10.0.21.219
111	10.0.21.220/31	10.0.21.220 – 10.0.21.221	10.0.21.221
112	10.0.21.222/31	10.0.21.222 – 10.0.21.223	10.0.21.223
113	10.0.21.224/31	10.0.21.224 – 10.0.21.225	10.0.21.225
114	10.0.21.226/31	10.0.21.226 – 10.0.21.227	10.0.21.227
115	10.0.21.228/31	10.0.21.228 – 10.0.21.229	10.0.21.229
116	10.0.21.230/31	10.0.21.230 – 10.0.21.231	10.0.21.231
117	10.0.21.232/31	10.0.21.232 – 10.0.21.233	10.0.21.233
118	10.0.21.234/31	10.0.21.234 – 10.0.21.235	10.0.21.235
119	10.0.21.236/31	10.0.21.236 – 10.0.21.237	10.0.21.237
120	10.0.21.238/31	10.0.21.238 – 10.0.21.239	10.0.21.239
121	10.0.21.240/31	10.0.21.240 – 10.0.21.241	10.0.21.241
122	10.0.21.242/31	10.0.21.242 – 10.0.21.243	10.0.21.243
123	10.0.21.244/31	10.0.21.244 – 10.0.21.245	10.0.21.245
124	10.0.21.246/31	10.0.21.246 – 10.0.21.247	10.0.21.247
125	10.0.21.248/31	10.0.21.248 – 10.0.21.249	10.0.21.249
126	10.0.21.250/31	10.0.21.250 – 10.0.21.251	10.0.21.251
127	10.0.21.252/31	10.0.21.252 – 10.0.21.253	10.0.21.253
128	10.0.21.254/31	10.0.21.254 – 10.0.21.255	10.0.21.255

01 / table

IPv4 CIDR prefix table.

Click a prefix longer than your network to split it into subnets.

prefix	subnet mask	addresses	hosts	in your /24
/0	0.0.0.0	4,294,967,296	4,294,967,294	-
/1	128.0.0.0	2,147,483,648	2,147,483,646	-
/2	192.0.0.0	1,073,741,824	1,073,741,822	-
/3	224.0.0.0	536,870,912	536,870,910	-
/4	240.0.0.0	268,435,456	268,435,454	-
/5	248.0.0.0	134,217,728	134,217,726	-
/6	252.0.0.0	67,108,864	67,108,862	-
/7	254.0.0.0	33,554,432	33,554,430	-
/8	255.0.0.0	16,777,216	16,777,214	-
/9	255.128.0.0	8,388,608	8,388,606	-
/10	255.192.0.0	4,194,304	4,194,302	-
/11	255.224.0.0	2,097,152	2,097,150	-
/12	255.240.0.0	1,048,576	1,048,574	-
/13	255.248.0.0	524,288	524,286	-
/14	255.252.0.0	262,144	262,142	-
/15	255.254.0.0	131,072	131,070	-
/16	255.255.0.0	65,536	65,534	-
/17	255.255.128.0	32,768	32,766	-
/18	255.255.192.0	16,384	16,382	-
/19	255.255.224.0	8,192	8,190	-
/20	255.255.240.0	4,096	4,094	-
/21	255.255.248.0	2,048	2,046	-
/22	255.255.252.0	1,024	1,022	-
/23	255.255.254.0	512	510	-
/24	255.255.255.0	256	254	1
/25	255.255.255.128	128	126	2 split →
/26	255.255.255.192	64	62	4 split →
/27	255.255.255.224	32	30	8 split →
/28	255.255.255.240	16	14	16 split →
/29	255.255.255.248	8	6	32 split →
/30	255.255.255.252	4	2	64 split →
/31	255.255.255.254	2	2	128 split →
/32	255.255.255.255	1	1	256 split →

02 / faq

About this calculator.

How do I use this subnet calculator?

▼

Type an IP address followed by a prefix, like 192.168.1.10/24, or by a subnet mask, like 192.168.1.10 255.255.255.0. Without a prefix it uses /24. Click a row in the table to split the network into smaller subnets.

Why are usable hosts always 2 fewer?

▼

The first address in a subnet is the network address and the last is the broadcast address, so neither can go to a device. The exceptions are /31 (point-to-point links, RFC 3021) and /32 (a single address), which use every address.

Can I use it from a terminal?

▼

Yes. curl 'ipku.in/en/tools/ipv4-subnet-calculator?q=192.168.1.10/24' returns the result as plain text.

Learn how to work it out →