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)10.2.208.0/21

network10.2.208.0/21

broadcast10.2.215.255

first host10.2.208.1

last host10.2.215.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classA

ipcalc 10.2.208.0/21

address00001010.00000010.11010000.00000000

subnet mask11111111.11111111.11111000.00000000

network00001010.00000010.11010000.00000000

broadcast00001010.00000010.11010111.11111111

green = network part, grey = host part

hex0x0a02d000

decimal167956480

reverse dns0.208.2.10.in-addr.arpa

ipv4-mapped::ffff:a02:d000

/21 split into /27 · 64 subnets

close ×

#	network	host range	broadcast
1	10.2.208.0/27	10.2.208.1 – 10.2.208.30	10.2.208.31
2	10.2.208.32/27	10.2.208.33 – 10.2.208.62	10.2.208.63
3	10.2.208.64/27	10.2.208.65 – 10.2.208.94	10.2.208.95
4	10.2.208.96/27	10.2.208.97 – 10.2.208.126	10.2.208.127
5	10.2.208.128/27	10.2.208.129 – 10.2.208.158	10.2.208.159
6	10.2.208.160/27	10.2.208.161 – 10.2.208.190	10.2.208.191
7	10.2.208.192/27	10.2.208.193 – 10.2.208.222	10.2.208.223
8	10.2.208.224/27	10.2.208.225 – 10.2.208.254	10.2.208.255
9	10.2.209.0/27	10.2.209.1 – 10.2.209.30	10.2.209.31
10	10.2.209.32/27	10.2.209.33 – 10.2.209.62	10.2.209.63
11	10.2.209.64/27	10.2.209.65 – 10.2.209.94	10.2.209.95
12	10.2.209.96/27	10.2.209.97 – 10.2.209.126	10.2.209.127
13	10.2.209.128/27	10.2.209.129 – 10.2.209.158	10.2.209.159
14	10.2.209.160/27	10.2.209.161 – 10.2.209.190	10.2.209.191
15	10.2.209.192/27	10.2.209.193 – 10.2.209.222	10.2.209.223
16	10.2.209.224/27	10.2.209.225 – 10.2.209.254	10.2.209.255
17	10.2.210.0/27	10.2.210.1 – 10.2.210.30	10.2.210.31
18	10.2.210.32/27	10.2.210.33 – 10.2.210.62	10.2.210.63
19	10.2.210.64/27	10.2.210.65 – 10.2.210.94	10.2.210.95
20	10.2.210.96/27	10.2.210.97 – 10.2.210.126	10.2.210.127
21	10.2.210.128/27	10.2.210.129 – 10.2.210.158	10.2.210.159
22	10.2.210.160/27	10.2.210.161 – 10.2.210.190	10.2.210.191
23	10.2.210.192/27	10.2.210.193 – 10.2.210.222	10.2.210.223
24	10.2.210.224/27	10.2.210.225 – 10.2.210.254	10.2.210.255
25	10.2.211.0/27	10.2.211.1 – 10.2.211.30	10.2.211.31
26	10.2.211.32/27	10.2.211.33 – 10.2.211.62	10.2.211.63
27	10.2.211.64/27	10.2.211.65 – 10.2.211.94	10.2.211.95
28	10.2.211.96/27	10.2.211.97 – 10.2.211.126	10.2.211.127
29	10.2.211.128/27	10.2.211.129 – 10.2.211.158	10.2.211.159
30	10.2.211.160/27	10.2.211.161 – 10.2.211.190	10.2.211.191
31	10.2.211.192/27	10.2.211.193 – 10.2.211.222	10.2.211.223
32	10.2.211.224/27	10.2.211.225 – 10.2.211.254	10.2.211.255
33	10.2.212.0/27	10.2.212.1 – 10.2.212.30	10.2.212.31
34	10.2.212.32/27	10.2.212.33 – 10.2.212.62	10.2.212.63
35	10.2.212.64/27	10.2.212.65 – 10.2.212.94	10.2.212.95
36	10.2.212.96/27	10.2.212.97 – 10.2.212.126	10.2.212.127
37	10.2.212.128/27	10.2.212.129 – 10.2.212.158	10.2.212.159
38	10.2.212.160/27	10.2.212.161 – 10.2.212.190	10.2.212.191
39	10.2.212.192/27	10.2.212.193 – 10.2.212.222	10.2.212.223
40	10.2.212.224/27	10.2.212.225 – 10.2.212.254	10.2.212.255
41	10.2.213.0/27	10.2.213.1 – 10.2.213.30	10.2.213.31
42	10.2.213.32/27	10.2.213.33 – 10.2.213.62	10.2.213.63
43	10.2.213.64/27	10.2.213.65 – 10.2.213.94	10.2.213.95
44	10.2.213.96/27	10.2.213.97 – 10.2.213.126	10.2.213.127
45	10.2.213.128/27	10.2.213.129 – 10.2.213.158	10.2.213.159
46	10.2.213.160/27	10.2.213.161 – 10.2.213.190	10.2.213.191
47	10.2.213.192/27	10.2.213.193 – 10.2.213.222	10.2.213.223
48	10.2.213.224/27	10.2.213.225 – 10.2.213.254	10.2.213.255
49	10.2.214.0/27	10.2.214.1 – 10.2.214.30	10.2.214.31
50	10.2.214.32/27	10.2.214.33 – 10.2.214.62	10.2.214.63
51	10.2.214.64/27	10.2.214.65 – 10.2.214.94	10.2.214.95
52	10.2.214.96/27	10.2.214.97 – 10.2.214.126	10.2.214.127
53	10.2.214.128/27	10.2.214.129 – 10.2.214.158	10.2.214.159
54	10.2.214.160/27	10.2.214.161 – 10.2.214.190	10.2.214.191
55	10.2.214.192/27	10.2.214.193 – 10.2.214.222	10.2.214.223
56	10.2.214.224/27	10.2.214.225 – 10.2.214.254	10.2.214.255
57	10.2.215.0/27	10.2.215.1 – 10.2.215.30	10.2.215.31
58	10.2.215.32/27	10.2.215.33 – 10.2.215.62	10.2.215.63
59	10.2.215.64/27	10.2.215.65 – 10.2.215.94	10.2.215.95
60	10.2.215.96/27	10.2.215.97 – 10.2.215.126	10.2.215.127
61	10.2.215.128/27	10.2.215.129 – 10.2.215.158	10.2.215.159
62	10.2.215.160/27	10.2.215.161 – 10.2.215.190	10.2.215.191
63	10.2.215.192/27	10.2.215.193 – 10.2.215.222	10.2.215.223
64	10.2.215.224/27	10.2.215.225 – 10.2.215.254	10.2.215.255

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 →