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)10.2.21.0/25

network10.2.21.0/25

broadcast10.2.21.127

first host10.2.21.1

last host10.2.21.126

subnet mask255.255.255.128

wildcard0.0.0.127

addresses128

usable hosts126

classA

ipcalc 10.2.21.0/25

address00001010.00000010.00010101.00000000

subnet mask11111111.11111111.11111111.10000000

network00001010.00000010.00010101.00000000

broadcast00001010.00000010.00010101.01111111

green = network part, grey = host part

hex0x0a021500

decimal167908608

reverse dns0.21.2.10.in-addr.arpa

ipv4-mapped::ffff:a02:1500

/25 split into /32 · 128 subnets

close ×

#	network	host range	broadcast
1	10.2.21.0/32	10.2.21.0 – 10.2.21.0	10.2.21.0
2	10.2.21.1/32	10.2.21.1 – 10.2.21.1	10.2.21.1
3	10.2.21.2/32	10.2.21.2 – 10.2.21.2	10.2.21.2
4	10.2.21.3/32	10.2.21.3 – 10.2.21.3	10.2.21.3
5	10.2.21.4/32	10.2.21.4 – 10.2.21.4	10.2.21.4
6	10.2.21.5/32	10.2.21.5 – 10.2.21.5	10.2.21.5
7	10.2.21.6/32	10.2.21.6 – 10.2.21.6	10.2.21.6
8	10.2.21.7/32	10.2.21.7 – 10.2.21.7	10.2.21.7
9	10.2.21.8/32	10.2.21.8 – 10.2.21.8	10.2.21.8
10	10.2.21.9/32	10.2.21.9 – 10.2.21.9	10.2.21.9
11	10.2.21.10/32	10.2.21.10 – 10.2.21.10	10.2.21.10
12	10.2.21.11/32	10.2.21.11 – 10.2.21.11	10.2.21.11
13	10.2.21.12/32	10.2.21.12 – 10.2.21.12	10.2.21.12
14	10.2.21.13/32	10.2.21.13 – 10.2.21.13	10.2.21.13
15	10.2.21.14/32	10.2.21.14 – 10.2.21.14	10.2.21.14
16	10.2.21.15/32	10.2.21.15 – 10.2.21.15	10.2.21.15
17	10.2.21.16/32	10.2.21.16 – 10.2.21.16	10.2.21.16
18	10.2.21.17/32	10.2.21.17 – 10.2.21.17	10.2.21.17
19	10.2.21.18/32	10.2.21.18 – 10.2.21.18	10.2.21.18
20	10.2.21.19/32	10.2.21.19 – 10.2.21.19	10.2.21.19
21	10.2.21.20/32	10.2.21.20 – 10.2.21.20	10.2.21.20
22	10.2.21.21/32	10.2.21.21 – 10.2.21.21	10.2.21.21
23	10.2.21.22/32	10.2.21.22 – 10.2.21.22	10.2.21.22
24	10.2.21.23/32	10.2.21.23 – 10.2.21.23	10.2.21.23
25	10.2.21.24/32	10.2.21.24 – 10.2.21.24	10.2.21.24
26	10.2.21.25/32	10.2.21.25 – 10.2.21.25	10.2.21.25
27	10.2.21.26/32	10.2.21.26 – 10.2.21.26	10.2.21.26
28	10.2.21.27/32	10.2.21.27 – 10.2.21.27	10.2.21.27
29	10.2.21.28/32	10.2.21.28 – 10.2.21.28	10.2.21.28
30	10.2.21.29/32	10.2.21.29 – 10.2.21.29	10.2.21.29
31	10.2.21.30/32	10.2.21.30 – 10.2.21.30	10.2.21.30
32	10.2.21.31/32	10.2.21.31 – 10.2.21.31	10.2.21.31
33	10.2.21.32/32	10.2.21.32 – 10.2.21.32	10.2.21.32
34	10.2.21.33/32	10.2.21.33 – 10.2.21.33	10.2.21.33
35	10.2.21.34/32	10.2.21.34 – 10.2.21.34	10.2.21.34
36	10.2.21.35/32	10.2.21.35 – 10.2.21.35	10.2.21.35
37	10.2.21.36/32	10.2.21.36 – 10.2.21.36	10.2.21.36
38	10.2.21.37/32	10.2.21.37 – 10.2.21.37	10.2.21.37
39	10.2.21.38/32	10.2.21.38 – 10.2.21.38	10.2.21.38
40	10.2.21.39/32	10.2.21.39 – 10.2.21.39	10.2.21.39
41	10.2.21.40/32	10.2.21.40 – 10.2.21.40	10.2.21.40
42	10.2.21.41/32	10.2.21.41 – 10.2.21.41	10.2.21.41
43	10.2.21.42/32	10.2.21.42 – 10.2.21.42	10.2.21.42
44	10.2.21.43/32	10.2.21.43 – 10.2.21.43	10.2.21.43
45	10.2.21.44/32	10.2.21.44 – 10.2.21.44	10.2.21.44
46	10.2.21.45/32	10.2.21.45 – 10.2.21.45	10.2.21.45
47	10.2.21.46/32	10.2.21.46 – 10.2.21.46	10.2.21.46
48	10.2.21.47/32	10.2.21.47 – 10.2.21.47	10.2.21.47
49	10.2.21.48/32	10.2.21.48 – 10.2.21.48	10.2.21.48
50	10.2.21.49/32	10.2.21.49 – 10.2.21.49	10.2.21.49
51	10.2.21.50/32	10.2.21.50 – 10.2.21.50	10.2.21.50
52	10.2.21.51/32	10.2.21.51 – 10.2.21.51	10.2.21.51
53	10.2.21.52/32	10.2.21.52 – 10.2.21.52	10.2.21.52
54	10.2.21.53/32	10.2.21.53 – 10.2.21.53	10.2.21.53
55	10.2.21.54/32	10.2.21.54 – 10.2.21.54	10.2.21.54
56	10.2.21.55/32	10.2.21.55 – 10.2.21.55	10.2.21.55
57	10.2.21.56/32	10.2.21.56 – 10.2.21.56	10.2.21.56
58	10.2.21.57/32	10.2.21.57 – 10.2.21.57	10.2.21.57
59	10.2.21.58/32	10.2.21.58 – 10.2.21.58	10.2.21.58
60	10.2.21.59/32	10.2.21.59 – 10.2.21.59	10.2.21.59
61	10.2.21.60/32	10.2.21.60 – 10.2.21.60	10.2.21.60
62	10.2.21.61/32	10.2.21.61 – 10.2.21.61	10.2.21.61
63	10.2.21.62/32	10.2.21.62 – 10.2.21.62	10.2.21.62
64	10.2.21.63/32	10.2.21.63 – 10.2.21.63	10.2.21.63
65	10.2.21.64/32	10.2.21.64 – 10.2.21.64	10.2.21.64
66	10.2.21.65/32	10.2.21.65 – 10.2.21.65	10.2.21.65
67	10.2.21.66/32	10.2.21.66 – 10.2.21.66	10.2.21.66
68	10.2.21.67/32	10.2.21.67 – 10.2.21.67	10.2.21.67
69	10.2.21.68/32	10.2.21.68 – 10.2.21.68	10.2.21.68
70	10.2.21.69/32	10.2.21.69 – 10.2.21.69	10.2.21.69
71	10.2.21.70/32	10.2.21.70 – 10.2.21.70	10.2.21.70
72	10.2.21.71/32	10.2.21.71 – 10.2.21.71	10.2.21.71
73	10.2.21.72/32	10.2.21.72 – 10.2.21.72	10.2.21.72
74	10.2.21.73/32	10.2.21.73 – 10.2.21.73	10.2.21.73
75	10.2.21.74/32	10.2.21.74 – 10.2.21.74	10.2.21.74
76	10.2.21.75/32	10.2.21.75 – 10.2.21.75	10.2.21.75
77	10.2.21.76/32	10.2.21.76 – 10.2.21.76	10.2.21.76
78	10.2.21.77/32	10.2.21.77 – 10.2.21.77	10.2.21.77
79	10.2.21.78/32	10.2.21.78 – 10.2.21.78	10.2.21.78
80	10.2.21.79/32	10.2.21.79 – 10.2.21.79	10.2.21.79
81	10.2.21.80/32	10.2.21.80 – 10.2.21.80	10.2.21.80
82	10.2.21.81/32	10.2.21.81 – 10.2.21.81	10.2.21.81
83	10.2.21.82/32	10.2.21.82 – 10.2.21.82	10.2.21.82
84	10.2.21.83/32	10.2.21.83 – 10.2.21.83	10.2.21.83
85	10.2.21.84/32	10.2.21.84 – 10.2.21.84	10.2.21.84
86	10.2.21.85/32	10.2.21.85 – 10.2.21.85	10.2.21.85
87	10.2.21.86/32	10.2.21.86 – 10.2.21.86	10.2.21.86
88	10.2.21.87/32	10.2.21.87 – 10.2.21.87	10.2.21.87
89	10.2.21.88/32	10.2.21.88 – 10.2.21.88	10.2.21.88
90	10.2.21.89/32	10.2.21.89 – 10.2.21.89	10.2.21.89
91	10.2.21.90/32	10.2.21.90 – 10.2.21.90	10.2.21.90
92	10.2.21.91/32	10.2.21.91 – 10.2.21.91	10.2.21.91
93	10.2.21.92/32	10.2.21.92 – 10.2.21.92	10.2.21.92
94	10.2.21.93/32	10.2.21.93 – 10.2.21.93	10.2.21.93
95	10.2.21.94/32	10.2.21.94 – 10.2.21.94	10.2.21.94
96	10.2.21.95/32	10.2.21.95 – 10.2.21.95	10.2.21.95
97	10.2.21.96/32	10.2.21.96 – 10.2.21.96	10.2.21.96
98	10.2.21.97/32	10.2.21.97 – 10.2.21.97	10.2.21.97
99	10.2.21.98/32	10.2.21.98 – 10.2.21.98	10.2.21.98
100	10.2.21.99/32	10.2.21.99 – 10.2.21.99	10.2.21.99
101	10.2.21.100/32	10.2.21.100 – 10.2.21.100	10.2.21.100
102	10.2.21.101/32	10.2.21.101 – 10.2.21.101	10.2.21.101
103	10.2.21.102/32	10.2.21.102 – 10.2.21.102	10.2.21.102
104	10.2.21.103/32	10.2.21.103 – 10.2.21.103	10.2.21.103
105	10.2.21.104/32	10.2.21.104 – 10.2.21.104	10.2.21.104
106	10.2.21.105/32	10.2.21.105 – 10.2.21.105	10.2.21.105
107	10.2.21.106/32	10.2.21.106 – 10.2.21.106	10.2.21.106
108	10.2.21.107/32	10.2.21.107 – 10.2.21.107	10.2.21.107
109	10.2.21.108/32	10.2.21.108 – 10.2.21.108	10.2.21.108
110	10.2.21.109/32	10.2.21.109 – 10.2.21.109	10.2.21.109
111	10.2.21.110/32	10.2.21.110 – 10.2.21.110	10.2.21.110
112	10.2.21.111/32	10.2.21.111 – 10.2.21.111	10.2.21.111
113	10.2.21.112/32	10.2.21.112 – 10.2.21.112	10.2.21.112
114	10.2.21.113/32	10.2.21.113 – 10.2.21.113	10.2.21.113
115	10.2.21.114/32	10.2.21.114 – 10.2.21.114	10.2.21.114
116	10.2.21.115/32	10.2.21.115 – 10.2.21.115	10.2.21.115
117	10.2.21.116/32	10.2.21.116 – 10.2.21.116	10.2.21.116
118	10.2.21.117/32	10.2.21.117 – 10.2.21.117	10.2.21.117
119	10.2.21.118/32	10.2.21.118 – 10.2.21.118	10.2.21.118
120	10.2.21.119/32	10.2.21.119 – 10.2.21.119	10.2.21.119
121	10.2.21.120/32	10.2.21.120 – 10.2.21.120	10.2.21.120
122	10.2.21.121/32	10.2.21.121 – 10.2.21.121	10.2.21.121
123	10.2.21.122/32	10.2.21.122 – 10.2.21.122	10.2.21.122
124	10.2.21.123/32	10.2.21.123 – 10.2.21.123	10.2.21.123
125	10.2.21.124/32	10.2.21.124 – 10.2.21.124	10.2.21.124
126	10.2.21.125/32	10.2.21.125 – 10.2.21.125	10.2.21.125
127	10.2.21.126/32	10.2.21.126 – 10.2.21.126	10.2.21.126
128	10.2.21.127/32	10.2.21.127 – 10.2.21.127	10.2.21.127

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 →