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)10.5.168.0/21

network10.5.168.0/21

broadcast10.5.175.255

first host10.5.168.1

last host10.5.175.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classA

ipcalc 10.5.168.0/21

address00001010.00000101.10101000.00000000

subnet mask11111111.11111111.11111000.00000000

network00001010.00000101.10101000.00000000

broadcast00001010.00000101.10101111.11111111

green = network part, grey = host part

hex0x0a05a800

decimal168142848

reverse dns0.168.5.10.in-addr.arpa

ipv4-mapped::ffff:a05:a800

/21 split into /27 · 64 subnets

close ×

#	network	host range	broadcast
1	10.5.168.0/27	10.5.168.1 – 10.5.168.30	10.5.168.31
2	10.5.168.32/27	10.5.168.33 – 10.5.168.62	10.5.168.63
3	10.5.168.64/27	10.5.168.65 – 10.5.168.94	10.5.168.95
4	10.5.168.96/27	10.5.168.97 – 10.5.168.126	10.5.168.127
5	10.5.168.128/27	10.5.168.129 – 10.5.168.158	10.5.168.159
6	10.5.168.160/27	10.5.168.161 – 10.5.168.190	10.5.168.191
7	10.5.168.192/27	10.5.168.193 – 10.5.168.222	10.5.168.223
8	10.5.168.224/27	10.5.168.225 – 10.5.168.254	10.5.168.255
9	10.5.169.0/27	10.5.169.1 – 10.5.169.30	10.5.169.31
10	10.5.169.32/27	10.5.169.33 – 10.5.169.62	10.5.169.63
11	10.5.169.64/27	10.5.169.65 – 10.5.169.94	10.5.169.95
12	10.5.169.96/27	10.5.169.97 – 10.5.169.126	10.5.169.127
13	10.5.169.128/27	10.5.169.129 – 10.5.169.158	10.5.169.159
14	10.5.169.160/27	10.5.169.161 – 10.5.169.190	10.5.169.191
15	10.5.169.192/27	10.5.169.193 – 10.5.169.222	10.5.169.223
16	10.5.169.224/27	10.5.169.225 – 10.5.169.254	10.5.169.255
17	10.5.170.0/27	10.5.170.1 – 10.5.170.30	10.5.170.31
18	10.5.170.32/27	10.5.170.33 – 10.5.170.62	10.5.170.63
19	10.5.170.64/27	10.5.170.65 – 10.5.170.94	10.5.170.95
20	10.5.170.96/27	10.5.170.97 – 10.5.170.126	10.5.170.127
21	10.5.170.128/27	10.5.170.129 – 10.5.170.158	10.5.170.159
22	10.5.170.160/27	10.5.170.161 – 10.5.170.190	10.5.170.191
23	10.5.170.192/27	10.5.170.193 – 10.5.170.222	10.5.170.223
24	10.5.170.224/27	10.5.170.225 – 10.5.170.254	10.5.170.255
25	10.5.171.0/27	10.5.171.1 – 10.5.171.30	10.5.171.31
26	10.5.171.32/27	10.5.171.33 – 10.5.171.62	10.5.171.63
27	10.5.171.64/27	10.5.171.65 – 10.5.171.94	10.5.171.95
28	10.5.171.96/27	10.5.171.97 – 10.5.171.126	10.5.171.127
29	10.5.171.128/27	10.5.171.129 – 10.5.171.158	10.5.171.159
30	10.5.171.160/27	10.5.171.161 – 10.5.171.190	10.5.171.191
31	10.5.171.192/27	10.5.171.193 – 10.5.171.222	10.5.171.223
32	10.5.171.224/27	10.5.171.225 – 10.5.171.254	10.5.171.255
33	10.5.172.0/27	10.5.172.1 – 10.5.172.30	10.5.172.31
34	10.5.172.32/27	10.5.172.33 – 10.5.172.62	10.5.172.63
35	10.5.172.64/27	10.5.172.65 – 10.5.172.94	10.5.172.95
36	10.5.172.96/27	10.5.172.97 – 10.5.172.126	10.5.172.127
37	10.5.172.128/27	10.5.172.129 – 10.5.172.158	10.5.172.159
38	10.5.172.160/27	10.5.172.161 – 10.5.172.190	10.5.172.191
39	10.5.172.192/27	10.5.172.193 – 10.5.172.222	10.5.172.223
40	10.5.172.224/27	10.5.172.225 – 10.5.172.254	10.5.172.255
41	10.5.173.0/27	10.5.173.1 – 10.5.173.30	10.5.173.31
42	10.5.173.32/27	10.5.173.33 – 10.5.173.62	10.5.173.63
43	10.5.173.64/27	10.5.173.65 – 10.5.173.94	10.5.173.95
44	10.5.173.96/27	10.5.173.97 – 10.5.173.126	10.5.173.127
45	10.5.173.128/27	10.5.173.129 – 10.5.173.158	10.5.173.159
46	10.5.173.160/27	10.5.173.161 – 10.5.173.190	10.5.173.191
47	10.5.173.192/27	10.5.173.193 – 10.5.173.222	10.5.173.223
48	10.5.173.224/27	10.5.173.225 – 10.5.173.254	10.5.173.255
49	10.5.174.0/27	10.5.174.1 – 10.5.174.30	10.5.174.31
50	10.5.174.32/27	10.5.174.33 – 10.5.174.62	10.5.174.63
51	10.5.174.64/27	10.5.174.65 – 10.5.174.94	10.5.174.95
52	10.5.174.96/27	10.5.174.97 – 10.5.174.126	10.5.174.127
53	10.5.174.128/27	10.5.174.129 – 10.5.174.158	10.5.174.159
54	10.5.174.160/27	10.5.174.161 – 10.5.174.190	10.5.174.191
55	10.5.174.192/27	10.5.174.193 – 10.5.174.222	10.5.174.223
56	10.5.174.224/27	10.5.174.225 – 10.5.174.254	10.5.174.255
57	10.5.175.0/27	10.5.175.1 – 10.5.175.30	10.5.175.31
58	10.5.175.32/27	10.5.175.33 – 10.5.175.62	10.5.175.63
59	10.5.175.64/27	10.5.175.65 – 10.5.175.94	10.5.175.95
60	10.5.175.96/27	10.5.175.97 – 10.5.175.126	10.5.175.127
61	10.5.175.128/27	10.5.175.129 – 10.5.175.158	10.5.175.159
62	10.5.175.160/27	10.5.175.161 – 10.5.175.190	10.5.175.191
63	10.5.175.192/27	10.5.175.193 – 10.5.175.222	10.5.175.223
64	10.5.175.224/27	10.5.175.225 – 10.5.175.254	10.5.175.255

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 →