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)10.0.21.128/25

network10.0.21.128/25

broadcast10.0.21.255

first host10.0.21.129

last host10.0.21.254

subnet mask255.255.255.128

wildcard0.0.0.127

addresses128

usable hosts126

classA

ipcalc 10.0.21.128/25

address00001010.00000000.00010101.10000000

subnet mask11111111.11111111.11111111.10000000

network00001010.00000000.00010101.10000000

broadcast00001010.00000000.00010101.11111111

green = network part, grey = host part

hex0x0a001580

decimal167777664

reverse dns128.21.0.10.in-addr.arpa

ipv4-mapped::ffff:a00:1580

/25 split into /32 · 128 subnets

close ×

#	network	host range	broadcast
1	10.0.21.128/32	10.0.21.128 – 10.0.21.128	10.0.21.128
2	10.0.21.129/32	10.0.21.129 – 10.0.21.129	10.0.21.129
3	10.0.21.130/32	10.0.21.130 – 10.0.21.130	10.0.21.130
4	10.0.21.131/32	10.0.21.131 – 10.0.21.131	10.0.21.131
5	10.0.21.132/32	10.0.21.132 – 10.0.21.132	10.0.21.132
6	10.0.21.133/32	10.0.21.133 – 10.0.21.133	10.0.21.133
7	10.0.21.134/32	10.0.21.134 – 10.0.21.134	10.0.21.134
8	10.0.21.135/32	10.0.21.135 – 10.0.21.135	10.0.21.135
9	10.0.21.136/32	10.0.21.136 – 10.0.21.136	10.0.21.136
10	10.0.21.137/32	10.0.21.137 – 10.0.21.137	10.0.21.137
11	10.0.21.138/32	10.0.21.138 – 10.0.21.138	10.0.21.138
12	10.0.21.139/32	10.0.21.139 – 10.0.21.139	10.0.21.139
13	10.0.21.140/32	10.0.21.140 – 10.0.21.140	10.0.21.140
14	10.0.21.141/32	10.0.21.141 – 10.0.21.141	10.0.21.141
15	10.0.21.142/32	10.0.21.142 – 10.0.21.142	10.0.21.142
16	10.0.21.143/32	10.0.21.143 – 10.0.21.143	10.0.21.143
17	10.0.21.144/32	10.0.21.144 – 10.0.21.144	10.0.21.144
18	10.0.21.145/32	10.0.21.145 – 10.0.21.145	10.0.21.145
19	10.0.21.146/32	10.0.21.146 – 10.0.21.146	10.0.21.146
20	10.0.21.147/32	10.0.21.147 – 10.0.21.147	10.0.21.147
21	10.0.21.148/32	10.0.21.148 – 10.0.21.148	10.0.21.148
22	10.0.21.149/32	10.0.21.149 – 10.0.21.149	10.0.21.149
23	10.0.21.150/32	10.0.21.150 – 10.0.21.150	10.0.21.150
24	10.0.21.151/32	10.0.21.151 – 10.0.21.151	10.0.21.151
25	10.0.21.152/32	10.0.21.152 – 10.0.21.152	10.0.21.152
26	10.0.21.153/32	10.0.21.153 – 10.0.21.153	10.0.21.153
27	10.0.21.154/32	10.0.21.154 – 10.0.21.154	10.0.21.154
28	10.0.21.155/32	10.0.21.155 – 10.0.21.155	10.0.21.155
29	10.0.21.156/32	10.0.21.156 – 10.0.21.156	10.0.21.156
30	10.0.21.157/32	10.0.21.157 – 10.0.21.157	10.0.21.157
31	10.0.21.158/32	10.0.21.158 – 10.0.21.158	10.0.21.158
32	10.0.21.159/32	10.0.21.159 – 10.0.21.159	10.0.21.159
33	10.0.21.160/32	10.0.21.160 – 10.0.21.160	10.0.21.160
34	10.0.21.161/32	10.0.21.161 – 10.0.21.161	10.0.21.161
35	10.0.21.162/32	10.0.21.162 – 10.0.21.162	10.0.21.162
36	10.0.21.163/32	10.0.21.163 – 10.0.21.163	10.0.21.163
37	10.0.21.164/32	10.0.21.164 – 10.0.21.164	10.0.21.164
38	10.0.21.165/32	10.0.21.165 – 10.0.21.165	10.0.21.165
39	10.0.21.166/32	10.0.21.166 – 10.0.21.166	10.0.21.166
40	10.0.21.167/32	10.0.21.167 – 10.0.21.167	10.0.21.167
41	10.0.21.168/32	10.0.21.168 – 10.0.21.168	10.0.21.168
42	10.0.21.169/32	10.0.21.169 – 10.0.21.169	10.0.21.169
43	10.0.21.170/32	10.0.21.170 – 10.0.21.170	10.0.21.170
44	10.0.21.171/32	10.0.21.171 – 10.0.21.171	10.0.21.171
45	10.0.21.172/32	10.0.21.172 – 10.0.21.172	10.0.21.172
46	10.0.21.173/32	10.0.21.173 – 10.0.21.173	10.0.21.173
47	10.0.21.174/32	10.0.21.174 – 10.0.21.174	10.0.21.174
48	10.0.21.175/32	10.0.21.175 – 10.0.21.175	10.0.21.175
49	10.0.21.176/32	10.0.21.176 – 10.0.21.176	10.0.21.176
50	10.0.21.177/32	10.0.21.177 – 10.0.21.177	10.0.21.177
51	10.0.21.178/32	10.0.21.178 – 10.0.21.178	10.0.21.178
52	10.0.21.179/32	10.0.21.179 – 10.0.21.179	10.0.21.179
53	10.0.21.180/32	10.0.21.180 – 10.0.21.180	10.0.21.180
54	10.0.21.181/32	10.0.21.181 – 10.0.21.181	10.0.21.181
55	10.0.21.182/32	10.0.21.182 – 10.0.21.182	10.0.21.182
56	10.0.21.183/32	10.0.21.183 – 10.0.21.183	10.0.21.183
57	10.0.21.184/32	10.0.21.184 – 10.0.21.184	10.0.21.184
58	10.0.21.185/32	10.0.21.185 – 10.0.21.185	10.0.21.185
59	10.0.21.186/32	10.0.21.186 – 10.0.21.186	10.0.21.186
60	10.0.21.187/32	10.0.21.187 – 10.0.21.187	10.0.21.187
61	10.0.21.188/32	10.0.21.188 – 10.0.21.188	10.0.21.188
62	10.0.21.189/32	10.0.21.189 – 10.0.21.189	10.0.21.189
63	10.0.21.190/32	10.0.21.190 – 10.0.21.190	10.0.21.190
64	10.0.21.191/32	10.0.21.191 – 10.0.21.191	10.0.21.191
65	10.0.21.192/32	10.0.21.192 – 10.0.21.192	10.0.21.192
66	10.0.21.193/32	10.0.21.193 – 10.0.21.193	10.0.21.193
67	10.0.21.194/32	10.0.21.194 – 10.0.21.194	10.0.21.194
68	10.0.21.195/32	10.0.21.195 – 10.0.21.195	10.0.21.195
69	10.0.21.196/32	10.0.21.196 – 10.0.21.196	10.0.21.196
70	10.0.21.197/32	10.0.21.197 – 10.0.21.197	10.0.21.197
71	10.0.21.198/32	10.0.21.198 – 10.0.21.198	10.0.21.198
72	10.0.21.199/32	10.0.21.199 – 10.0.21.199	10.0.21.199
73	10.0.21.200/32	10.0.21.200 – 10.0.21.200	10.0.21.200
74	10.0.21.201/32	10.0.21.201 – 10.0.21.201	10.0.21.201
75	10.0.21.202/32	10.0.21.202 – 10.0.21.202	10.0.21.202
76	10.0.21.203/32	10.0.21.203 – 10.0.21.203	10.0.21.203
77	10.0.21.204/32	10.0.21.204 – 10.0.21.204	10.0.21.204
78	10.0.21.205/32	10.0.21.205 – 10.0.21.205	10.0.21.205
79	10.0.21.206/32	10.0.21.206 – 10.0.21.206	10.0.21.206
80	10.0.21.207/32	10.0.21.207 – 10.0.21.207	10.0.21.207
81	10.0.21.208/32	10.0.21.208 – 10.0.21.208	10.0.21.208
82	10.0.21.209/32	10.0.21.209 – 10.0.21.209	10.0.21.209
83	10.0.21.210/32	10.0.21.210 – 10.0.21.210	10.0.21.210
84	10.0.21.211/32	10.0.21.211 – 10.0.21.211	10.0.21.211
85	10.0.21.212/32	10.0.21.212 – 10.0.21.212	10.0.21.212
86	10.0.21.213/32	10.0.21.213 – 10.0.21.213	10.0.21.213
87	10.0.21.214/32	10.0.21.214 – 10.0.21.214	10.0.21.214
88	10.0.21.215/32	10.0.21.215 – 10.0.21.215	10.0.21.215
89	10.0.21.216/32	10.0.21.216 – 10.0.21.216	10.0.21.216
90	10.0.21.217/32	10.0.21.217 – 10.0.21.217	10.0.21.217
91	10.0.21.218/32	10.0.21.218 – 10.0.21.218	10.0.21.218
92	10.0.21.219/32	10.0.21.219 – 10.0.21.219	10.0.21.219
93	10.0.21.220/32	10.0.21.220 – 10.0.21.220	10.0.21.220
94	10.0.21.221/32	10.0.21.221 – 10.0.21.221	10.0.21.221
95	10.0.21.222/32	10.0.21.222 – 10.0.21.222	10.0.21.222
96	10.0.21.223/32	10.0.21.223 – 10.0.21.223	10.0.21.223
97	10.0.21.224/32	10.0.21.224 – 10.0.21.224	10.0.21.224
98	10.0.21.225/32	10.0.21.225 – 10.0.21.225	10.0.21.225
99	10.0.21.226/32	10.0.21.226 – 10.0.21.226	10.0.21.226
100	10.0.21.227/32	10.0.21.227 – 10.0.21.227	10.0.21.227
101	10.0.21.228/32	10.0.21.228 – 10.0.21.228	10.0.21.228
102	10.0.21.229/32	10.0.21.229 – 10.0.21.229	10.0.21.229
103	10.0.21.230/32	10.0.21.230 – 10.0.21.230	10.0.21.230
104	10.0.21.231/32	10.0.21.231 – 10.0.21.231	10.0.21.231
105	10.0.21.232/32	10.0.21.232 – 10.0.21.232	10.0.21.232
106	10.0.21.233/32	10.0.21.233 – 10.0.21.233	10.0.21.233
107	10.0.21.234/32	10.0.21.234 – 10.0.21.234	10.0.21.234
108	10.0.21.235/32	10.0.21.235 – 10.0.21.235	10.0.21.235
109	10.0.21.236/32	10.0.21.236 – 10.0.21.236	10.0.21.236
110	10.0.21.237/32	10.0.21.237 – 10.0.21.237	10.0.21.237
111	10.0.21.238/32	10.0.21.238 – 10.0.21.238	10.0.21.238
112	10.0.21.239/32	10.0.21.239 – 10.0.21.239	10.0.21.239
113	10.0.21.240/32	10.0.21.240 – 10.0.21.240	10.0.21.240
114	10.0.21.241/32	10.0.21.241 – 10.0.21.241	10.0.21.241
115	10.0.21.242/32	10.0.21.242 – 10.0.21.242	10.0.21.242
116	10.0.21.243/32	10.0.21.243 – 10.0.21.243	10.0.21.243
117	10.0.21.244/32	10.0.21.244 – 10.0.21.244	10.0.21.244
118	10.0.21.245/32	10.0.21.245 – 10.0.21.245	10.0.21.245
119	10.0.21.246/32	10.0.21.246 – 10.0.21.246	10.0.21.246
120	10.0.21.247/32	10.0.21.247 – 10.0.21.247	10.0.21.247
121	10.0.21.248/32	10.0.21.248 – 10.0.21.248	10.0.21.248
122	10.0.21.249/32	10.0.21.249 – 10.0.21.249	10.0.21.249
123	10.0.21.250/32	10.0.21.250 – 10.0.21.250	10.0.21.250
124	10.0.21.251/32	10.0.21.251 – 10.0.21.251	10.0.21.251
125	10.0.21.252/32	10.0.21.252 – 10.0.21.252	10.0.21.252
126	10.0.21.253/32	10.0.21.253 – 10.0.21.253	10.0.21.253
127	10.0.21.254/32	10.0.21.254 – 10.0.21.254	10.0.21.254
128	10.0.21.255/32	10.0.21.255 – 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 /25
/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	-
/25	255.255.255.128	128	126	1
/26	255.255.255.192	64	62	2 split →
/27	255.255.255.224	32	30	4 split →
/28	255.255.255.240	16	14	8 split →
/29	255.255.255.248	8	6	16 split →
/30	255.255.255.252	4	2	32 split →
/31	255.255.255.254	2	2	64 split →
/32	255.255.255.255	1	1	128 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 →