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)10.2.0.0/21

network10.2.0.0/21

broadcast10.2.7.255

first host10.2.0.1

last host10.2.7.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classA

ipcalc 10.2.0.0/21

address00001010.00000010.00000000.00000000

subnet mask11111111.11111111.11111000.00000000

network00001010.00000010.00000000.00000000

broadcast00001010.00000010.00000111.11111111

green = network part, grey = host part

hex0x0a020000

decimal167903232

reverse dns0.0.2.10.in-addr.arpa

ipv4-mapped::ffff:a02:0

/21 split into /27 · 64 subnets

close ×

#	network	host range	broadcast
1	10.2.0.0/27	10.2.0.1 – 10.2.0.30	10.2.0.31
2	10.2.0.32/27	10.2.0.33 – 10.2.0.62	10.2.0.63
3	10.2.0.64/27	10.2.0.65 – 10.2.0.94	10.2.0.95
4	10.2.0.96/27	10.2.0.97 – 10.2.0.126	10.2.0.127
5	10.2.0.128/27	10.2.0.129 – 10.2.0.158	10.2.0.159
6	10.2.0.160/27	10.2.0.161 – 10.2.0.190	10.2.0.191
7	10.2.0.192/27	10.2.0.193 – 10.2.0.222	10.2.0.223
8	10.2.0.224/27	10.2.0.225 – 10.2.0.254	10.2.0.255
9	10.2.1.0/27	10.2.1.1 – 10.2.1.30	10.2.1.31
10	10.2.1.32/27	10.2.1.33 – 10.2.1.62	10.2.1.63
11	10.2.1.64/27	10.2.1.65 – 10.2.1.94	10.2.1.95
12	10.2.1.96/27	10.2.1.97 – 10.2.1.126	10.2.1.127
13	10.2.1.128/27	10.2.1.129 – 10.2.1.158	10.2.1.159
14	10.2.1.160/27	10.2.1.161 – 10.2.1.190	10.2.1.191
15	10.2.1.192/27	10.2.1.193 – 10.2.1.222	10.2.1.223
16	10.2.1.224/27	10.2.1.225 – 10.2.1.254	10.2.1.255
17	10.2.2.0/27	10.2.2.1 – 10.2.2.30	10.2.2.31
18	10.2.2.32/27	10.2.2.33 – 10.2.2.62	10.2.2.63
19	10.2.2.64/27	10.2.2.65 – 10.2.2.94	10.2.2.95
20	10.2.2.96/27	10.2.2.97 – 10.2.2.126	10.2.2.127
21	10.2.2.128/27	10.2.2.129 – 10.2.2.158	10.2.2.159
22	10.2.2.160/27	10.2.2.161 – 10.2.2.190	10.2.2.191
23	10.2.2.192/27	10.2.2.193 – 10.2.2.222	10.2.2.223
24	10.2.2.224/27	10.2.2.225 – 10.2.2.254	10.2.2.255
25	10.2.3.0/27	10.2.3.1 – 10.2.3.30	10.2.3.31
26	10.2.3.32/27	10.2.3.33 – 10.2.3.62	10.2.3.63
27	10.2.3.64/27	10.2.3.65 – 10.2.3.94	10.2.3.95
28	10.2.3.96/27	10.2.3.97 – 10.2.3.126	10.2.3.127
29	10.2.3.128/27	10.2.3.129 – 10.2.3.158	10.2.3.159
30	10.2.3.160/27	10.2.3.161 – 10.2.3.190	10.2.3.191
31	10.2.3.192/27	10.2.3.193 – 10.2.3.222	10.2.3.223
32	10.2.3.224/27	10.2.3.225 – 10.2.3.254	10.2.3.255
33	10.2.4.0/27	10.2.4.1 – 10.2.4.30	10.2.4.31
34	10.2.4.32/27	10.2.4.33 – 10.2.4.62	10.2.4.63
35	10.2.4.64/27	10.2.4.65 – 10.2.4.94	10.2.4.95
36	10.2.4.96/27	10.2.4.97 – 10.2.4.126	10.2.4.127
37	10.2.4.128/27	10.2.4.129 – 10.2.4.158	10.2.4.159
38	10.2.4.160/27	10.2.4.161 – 10.2.4.190	10.2.4.191
39	10.2.4.192/27	10.2.4.193 – 10.2.4.222	10.2.4.223
40	10.2.4.224/27	10.2.4.225 – 10.2.4.254	10.2.4.255
41	10.2.5.0/27	10.2.5.1 – 10.2.5.30	10.2.5.31
42	10.2.5.32/27	10.2.5.33 – 10.2.5.62	10.2.5.63
43	10.2.5.64/27	10.2.5.65 – 10.2.5.94	10.2.5.95
44	10.2.5.96/27	10.2.5.97 – 10.2.5.126	10.2.5.127
45	10.2.5.128/27	10.2.5.129 – 10.2.5.158	10.2.5.159
46	10.2.5.160/27	10.2.5.161 – 10.2.5.190	10.2.5.191
47	10.2.5.192/27	10.2.5.193 – 10.2.5.222	10.2.5.223
48	10.2.5.224/27	10.2.5.225 – 10.2.5.254	10.2.5.255
49	10.2.6.0/27	10.2.6.1 – 10.2.6.30	10.2.6.31
50	10.2.6.32/27	10.2.6.33 – 10.2.6.62	10.2.6.63
51	10.2.6.64/27	10.2.6.65 – 10.2.6.94	10.2.6.95
52	10.2.6.96/27	10.2.6.97 – 10.2.6.126	10.2.6.127
53	10.2.6.128/27	10.2.6.129 – 10.2.6.158	10.2.6.159
54	10.2.6.160/27	10.2.6.161 – 10.2.6.190	10.2.6.191
55	10.2.6.192/27	10.2.6.193 – 10.2.6.222	10.2.6.223
56	10.2.6.224/27	10.2.6.225 – 10.2.6.254	10.2.6.255
57	10.2.7.0/27	10.2.7.1 – 10.2.7.30	10.2.7.31
58	10.2.7.32/27	10.2.7.33 – 10.2.7.62	10.2.7.63
59	10.2.7.64/27	10.2.7.65 – 10.2.7.94	10.2.7.95
60	10.2.7.96/27	10.2.7.97 – 10.2.7.126	10.2.7.127
61	10.2.7.128/27	10.2.7.129 – 10.2.7.158	10.2.7.159
62	10.2.7.160/27	10.2.7.161 – 10.2.7.190	10.2.7.191
63	10.2.7.192/27	10.2.7.193 – 10.2.7.222	10.2.7.223
64	10.2.7.224/27	10.2.7.225 – 10.2.7.254	10.2.7.255

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 →