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)10.0.128.0/21

network10.0.128.0/21

broadcast10.0.135.255

first host10.0.128.1

last host10.0.135.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classA

ipcalc 10.0.128.0/21

address00001010.00000000.10000000.00000000

subnet mask11111111.11111111.11111000.00000000

network00001010.00000000.10000000.00000000

broadcast00001010.00000000.10000111.11111111

green = network part, grey = host part

hex0x0a008000

decimal167804928

reverse dns0.128.0.10.in-addr.arpa

ipv4-mapped::ffff:a00:8000

/21 split into /28 · 128 subnets

close ×

#	network	host range	broadcast
1	10.0.128.0/28	10.0.128.1 – 10.0.128.14	10.0.128.15
2	10.0.128.16/28	10.0.128.17 – 10.0.128.30	10.0.128.31
3	10.0.128.32/28	10.0.128.33 – 10.0.128.46	10.0.128.47
4	10.0.128.48/28	10.0.128.49 – 10.0.128.62	10.0.128.63
5	10.0.128.64/28	10.0.128.65 – 10.0.128.78	10.0.128.79
6	10.0.128.80/28	10.0.128.81 – 10.0.128.94	10.0.128.95
7	10.0.128.96/28	10.0.128.97 – 10.0.128.110	10.0.128.111
8	10.0.128.112/28	10.0.128.113 – 10.0.128.126	10.0.128.127
9	10.0.128.128/28	10.0.128.129 – 10.0.128.142	10.0.128.143
10	10.0.128.144/28	10.0.128.145 – 10.0.128.158	10.0.128.159
11	10.0.128.160/28	10.0.128.161 – 10.0.128.174	10.0.128.175
12	10.0.128.176/28	10.0.128.177 – 10.0.128.190	10.0.128.191
13	10.0.128.192/28	10.0.128.193 – 10.0.128.206	10.0.128.207
14	10.0.128.208/28	10.0.128.209 – 10.0.128.222	10.0.128.223
15	10.0.128.224/28	10.0.128.225 – 10.0.128.238	10.0.128.239
16	10.0.128.240/28	10.0.128.241 – 10.0.128.254	10.0.128.255
17	10.0.129.0/28	10.0.129.1 – 10.0.129.14	10.0.129.15
18	10.0.129.16/28	10.0.129.17 – 10.0.129.30	10.0.129.31
19	10.0.129.32/28	10.0.129.33 – 10.0.129.46	10.0.129.47
20	10.0.129.48/28	10.0.129.49 – 10.0.129.62	10.0.129.63
21	10.0.129.64/28	10.0.129.65 – 10.0.129.78	10.0.129.79
22	10.0.129.80/28	10.0.129.81 – 10.0.129.94	10.0.129.95
23	10.0.129.96/28	10.0.129.97 – 10.0.129.110	10.0.129.111
24	10.0.129.112/28	10.0.129.113 – 10.0.129.126	10.0.129.127
25	10.0.129.128/28	10.0.129.129 – 10.0.129.142	10.0.129.143
26	10.0.129.144/28	10.0.129.145 – 10.0.129.158	10.0.129.159
27	10.0.129.160/28	10.0.129.161 – 10.0.129.174	10.0.129.175
28	10.0.129.176/28	10.0.129.177 – 10.0.129.190	10.0.129.191
29	10.0.129.192/28	10.0.129.193 – 10.0.129.206	10.0.129.207
30	10.0.129.208/28	10.0.129.209 – 10.0.129.222	10.0.129.223
31	10.0.129.224/28	10.0.129.225 – 10.0.129.238	10.0.129.239
32	10.0.129.240/28	10.0.129.241 – 10.0.129.254	10.0.129.255
33	10.0.130.0/28	10.0.130.1 – 10.0.130.14	10.0.130.15
34	10.0.130.16/28	10.0.130.17 – 10.0.130.30	10.0.130.31
35	10.0.130.32/28	10.0.130.33 – 10.0.130.46	10.0.130.47
36	10.0.130.48/28	10.0.130.49 – 10.0.130.62	10.0.130.63
37	10.0.130.64/28	10.0.130.65 – 10.0.130.78	10.0.130.79
38	10.0.130.80/28	10.0.130.81 – 10.0.130.94	10.0.130.95
39	10.0.130.96/28	10.0.130.97 – 10.0.130.110	10.0.130.111
40	10.0.130.112/28	10.0.130.113 – 10.0.130.126	10.0.130.127
41	10.0.130.128/28	10.0.130.129 – 10.0.130.142	10.0.130.143
42	10.0.130.144/28	10.0.130.145 – 10.0.130.158	10.0.130.159
43	10.0.130.160/28	10.0.130.161 – 10.0.130.174	10.0.130.175
44	10.0.130.176/28	10.0.130.177 – 10.0.130.190	10.0.130.191
45	10.0.130.192/28	10.0.130.193 – 10.0.130.206	10.0.130.207
46	10.0.130.208/28	10.0.130.209 – 10.0.130.222	10.0.130.223
47	10.0.130.224/28	10.0.130.225 – 10.0.130.238	10.0.130.239
48	10.0.130.240/28	10.0.130.241 – 10.0.130.254	10.0.130.255
49	10.0.131.0/28	10.0.131.1 – 10.0.131.14	10.0.131.15
50	10.0.131.16/28	10.0.131.17 – 10.0.131.30	10.0.131.31
51	10.0.131.32/28	10.0.131.33 – 10.0.131.46	10.0.131.47
52	10.0.131.48/28	10.0.131.49 – 10.0.131.62	10.0.131.63
53	10.0.131.64/28	10.0.131.65 – 10.0.131.78	10.0.131.79
54	10.0.131.80/28	10.0.131.81 – 10.0.131.94	10.0.131.95
55	10.0.131.96/28	10.0.131.97 – 10.0.131.110	10.0.131.111
56	10.0.131.112/28	10.0.131.113 – 10.0.131.126	10.0.131.127
57	10.0.131.128/28	10.0.131.129 – 10.0.131.142	10.0.131.143
58	10.0.131.144/28	10.0.131.145 – 10.0.131.158	10.0.131.159
59	10.0.131.160/28	10.0.131.161 – 10.0.131.174	10.0.131.175
60	10.0.131.176/28	10.0.131.177 – 10.0.131.190	10.0.131.191
61	10.0.131.192/28	10.0.131.193 – 10.0.131.206	10.0.131.207
62	10.0.131.208/28	10.0.131.209 – 10.0.131.222	10.0.131.223
63	10.0.131.224/28	10.0.131.225 – 10.0.131.238	10.0.131.239
64	10.0.131.240/28	10.0.131.241 – 10.0.131.254	10.0.131.255
65	10.0.132.0/28	10.0.132.1 – 10.0.132.14	10.0.132.15
66	10.0.132.16/28	10.0.132.17 – 10.0.132.30	10.0.132.31
67	10.0.132.32/28	10.0.132.33 – 10.0.132.46	10.0.132.47
68	10.0.132.48/28	10.0.132.49 – 10.0.132.62	10.0.132.63
69	10.0.132.64/28	10.0.132.65 – 10.0.132.78	10.0.132.79
70	10.0.132.80/28	10.0.132.81 – 10.0.132.94	10.0.132.95
71	10.0.132.96/28	10.0.132.97 – 10.0.132.110	10.0.132.111
72	10.0.132.112/28	10.0.132.113 – 10.0.132.126	10.0.132.127
73	10.0.132.128/28	10.0.132.129 – 10.0.132.142	10.0.132.143
74	10.0.132.144/28	10.0.132.145 – 10.0.132.158	10.0.132.159
75	10.0.132.160/28	10.0.132.161 – 10.0.132.174	10.0.132.175
76	10.0.132.176/28	10.0.132.177 – 10.0.132.190	10.0.132.191
77	10.0.132.192/28	10.0.132.193 – 10.0.132.206	10.0.132.207
78	10.0.132.208/28	10.0.132.209 – 10.0.132.222	10.0.132.223
79	10.0.132.224/28	10.0.132.225 – 10.0.132.238	10.0.132.239
80	10.0.132.240/28	10.0.132.241 – 10.0.132.254	10.0.132.255
81	10.0.133.0/28	10.0.133.1 – 10.0.133.14	10.0.133.15
82	10.0.133.16/28	10.0.133.17 – 10.0.133.30	10.0.133.31
83	10.0.133.32/28	10.0.133.33 – 10.0.133.46	10.0.133.47
84	10.0.133.48/28	10.0.133.49 – 10.0.133.62	10.0.133.63
85	10.0.133.64/28	10.0.133.65 – 10.0.133.78	10.0.133.79
86	10.0.133.80/28	10.0.133.81 – 10.0.133.94	10.0.133.95
87	10.0.133.96/28	10.0.133.97 – 10.0.133.110	10.0.133.111
88	10.0.133.112/28	10.0.133.113 – 10.0.133.126	10.0.133.127
89	10.0.133.128/28	10.0.133.129 – 10.0.133.142	10.0.133.143
90	10.0.133.144/28	10.0.133.145 – 10.0.133.158	10.0.133.159
91	10.0.133.160/28	10.0.133.161 – 10.0.133.174	10.0.133.175
92	10.0.133.176/28	10.0.133.177 – 10.0.133.190	10.0.133.191
93	10.0.133.192/28	10.0.133.193 – 10.0.133.206	10.0.133.207
94	10.0.133.208/28	10.0.133.209 – 10.0.133.222	10.0.133.223
95	10.0.133.224/28	10.0.133.225 – 10.0.133.238	10.0.133.239
96	10.0.133.240/28	10.0.133.241 – 10.0.133.254	10.0.133.255
97	10.0.134.0/28	10.0.134.1 – 10.0.134.14	10.0.134.15
98	10.0.134.16/28	10.0.134.17 – 10.0.134.30	10.0.134.31
99	10.0.134.32/28	10.0.134.33 – 10.0.134.46	10.0.134.47
100	10.0.134.48/28	10.0.134.49 – 10.0.134.62	10.0.134.63
101	10.0.134.64/28	10.0.134.65 – 10.0.134.78	10.0.134.79
102	10.0.134.80/28	10.0.134.81 – 10.0.134.94	10.0.134.95
103	10.0.134.96/28	10.0.134.97 – 10.0.134.110	10.0.134.111
104	10.0.134.112/28	10.0.134.113 – 10.0.134.126	10.0.134.127
105	10.0.134.128/28	10.0.134.129 – 10.0.134.142	10.0.134.143
106	10.0.134.144/28	10.0.134.145 – 10.0.134.158	10.0.134.159
107	10.0.134.160/28	10.0.134.161 – 10.0.134.174	10.0.134.175
108	10.0.134.176/28	10.0.134.177 – 10.0.134.190	10.0.134.191
109	10.0.134.192/28	10.0.134.193 – 10.0.134.206	10.0.134.207
110	10.0.134.208/28	10.0.134.209 – 10.0.134.222	10.0.134.223
111	10.0.134.224/28	10.0.134.225 – 10.0.134.238	10.0.134.239
112	10.0.134.240/28	10.0.134.241 – 10.0.134.254	10.0.134.255
113	10.0.135.0/28	10.0.135.1 – 10.0.135.14	10.0.135.15
114	10.0.135.16/28	10.0.135.17 – 10.0.135.30	10.0.135.31
115	10.0.135.32/28	10.0.135.33 – 10.0.135.46	10.0.135.47
116	10.0.135.48/28	10.0.135.49 – 10.0.135.62	10.0.135.63
117	10.0.135.64/28	10.0.135.65 – 10.0.135.78	10.0.135.79
118	10.0.135.80/28	10.0.135.81 – 10.0.135.94	10.0.135.95
119	10.0.135.96/28	10.0.135.97 – 10.0.135.110	10.0.135.111
120	10.0.135.112/28	10.0.135.113 – 10.0.135.126	10.0.135.127
121	10.0.135.128/28	10.0.135.129 – 10.0.135.142	10.0.135.143
122	10.0.135.144/28	10.0.135.145 – 10.0.135.158	10.0.135.159
123	10.0.135.160/28	10.0.135.161 – 10.0.135.174	10.0.135.175
124	10.0.135.176/28	10.0.135.177 – 10.0.135.190	10.0.135.191
125	10.0.135.192/28	10.0.135.193 – 10.0.135.206	10.0.135.207
126	10.0.135.208/28	10.0.135.209 – 10.0.135.222	10.0.135.223
127	10.0.135.224/28	10.0.135.225 – 10.0.135.238	10.0.135.239
128	10.0.135.240/28	10.0.135.241 – 10.0.135.254	10.0.135.255

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 /21
/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	1
/22	255.255.252.0	1,024	1,022	2 split →
/23	255.255.254.0	512	510	4 split →
/24	255.255.255.0	256	254	8 split →
/25	255.255.255.128	128	126	16 split →
/26	255.255.255.192	64	62	32 split →
/27	255.255.255.224	32	30	64 split →
/28	255.255.255.240	16	14	128 split →
/29	255.255.255.248	8	6	256 split →
/30	255.255.255.252	4	2	512 split →
/31	255.255.255.254	2	2	1,024 split →
/32	255.255.255.255	1	1	2,048 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 →