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)10.0.8.0/21

network10.0.8.0/21

broadcast10.0.15.255

first host10.0.8.1

last host10.0.15.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classA

ipcalc 10.0.8.0/21

address00001010.00000000.00001000.00000000

subnet mask11111111.11111111.11111000.00000000

network00001010.00000000.00001000.00000000

broadcast00001010.00000000.00001111.11111111

green = network part, grey = host part

hex0x0a000800

decimal167774208

reverse dns0.8.0.10.in-addr.arpa

ipv4-mapped::ffff:a00:800

/21 split into /27 · 64 subnets

close ×

#	network	host range	broadcast
1	10.0.8.0/27	10.0.8.1 – 10.0.8.30	10.0.8.31
2	10.0.8.32/27	10.0.8.33 – 10.0.8.62	10.0.8.63
3	10.0.8.64/27	10.0.8.65 – 10.0.8.94	10.0.8.95
4	10.0.8.96/27	10.0.8.97 – 10.0.8.126	10.0.8.127
5	10.0.8.128/27	10.0.8.129 – 10.0.8.158	10.0.8.159
6	10.0.8.160/27	10.0.8.161 – 10.0.8.190	10.0.8.191
7	10.0.8.192/27	10.0.8.193 – 10.0.8.222	10.0.8.223
8	10.0.8.224/27	10.0.8.225 – 10.0.8.254	10.0.8.255
9	10.0.9.0/27	10.0.9.1 – 10.0.9.30	10.0.9.31
10	10.0.9.32/27	10.0.9.33 – 10.0.9.62	10.0.9.63
11	10.0.9.64/27	10.0.9.65 – 10.0.9.94	10.0.9.95
12	10.0.9.96/27	10.0.9.97 – 10.0.9.126	10.0.9.127
13	10.0.9.128/27	10.0.9.129 – 10.0.9.158	10.0.9.159
14	10.0.9.160/27	10.0.9.161 – 10.0.9.190	10.0.9.191
15	10.0.9.192/27	10.0.9.193 – 10.0.9.222	10.0.9.223
16	10.0.9.224/27	10.0.9.225 – 10.0.9.254	10.0.9.255
17	10.0.10.0/27	10.0.10.1 – 10.0.10.30	10.0.10.31
18	10.0.10.32/27	10.0.10.33 – 10.0.10.62	10.0.10.63
19	10.0.10.64/27	10.0.10.65 – 10.0.10.94	10.0.10.95
20	10.0.10.96/27	10.0.10.97 – 10.0.10.126	10.0.10.127
21	10.0.10.128/27	10.0.10.129 – 10.0.10.158	10.0.10.159
22	10.0.10.160/27	10.0.10.161 – 10.0.10.190	10.0.10.191
23	10.0.10.192/27	10.0.10.193 – 10.0.10.222	10.0.10.223
24	10.0.10.224/27	10.0.10.225 – 10.0.10.254	10.0.10.255
25	10.0.11.0/27	10.0.11.1 – 10.0.11.30	10.0.11.31
26	10.0.11.32/27	10.0.11.33 – 10.0.11.62	10.0.11.63
27	10.0.11.64/27	10.0.11.65 – 10.0.11.94	10.0.11.95
28	10.0.11.96/27	10.0.11.97 – 10.0.11.126	10.0.11.127
29	10.0.11.128/27	10.0.11.129 – 10.0.11.158	10.0.11.159
30	10.0.11.160/27	10.0.11.161 – 10.0.11.190	10.0.11.191
31	10.0.11.192/27	10.0.11.193 – 10.0.11.222	10.0.11.223
32	10.0.11.224/27	10.0.11.225 – 10.0.11.254	10.0.11.255
33	10.0.12.0/27	10.0.12.1 – 10.0.12.30	10.0.12.31
34	10.0.12.32/27	10.0.12.33 – 10.0.12.62	10.0.12.63
35	10.0.12.64/27	10.0.12.65 – 10.0.12.94	10.0.12.95
36	10.0.12.96/27	10.0.12.97 – 10.0.12.126	10.0.12.127
37	10.0.12.128/27	10.0.12.129 – 10.0.12.158	10.0.12.159
38	10.0.12.160/27	10.0.12.161 – 10.0.12.190	10.0.12.191
39	10.0.12.192/27	10.0.12.193 – 10.0.12.222	10.0.12.223
40	10.0.12.224/27	10.0.12.225 – 10.0.12.254	10.0.12.255
41	10.0.13.0/27	10.0.13.1 – 10.0.13.30	10.0.13.31
42	10.0.13.32/27	10.0.13.33 – 10.0.13.62	10.0.13.63
43	10.0.13.64/27	10.0.13.65 – 10.0.13.94	10.0.13.95
44	10.0.13.96/27	10.0.13.97 – 10.0.13.126	10.0.13.127
45	10.0.13.128/27	10.0.13.129 – 10.0.13.158	10.0.13.159
46	10.0.13.160/27	10.0.13.161 – 10.0.13.190	10.0.13.191
47	10.0.13.192/27	10.0.13.193 – 10.0.13.222	10.0.13.223
48	10.0.13.224/27	10.0.13.225 – 10.0.13.254	10.0.13.255
49	10.0.14.0/27	10.0.14.1 – 10.0.14.30	10.0.14.31
50	10.0.14.32/27	10.0.14.33 – 10.0.14.62	10.0.14.63
51	10.0.14.64/27	10.0.14.65 – 10.0.14.94	10.0.14.95
52	10.0.14.96/27	10.0.14.97 – 10.0.14.126	10.0.14.127
53	10.0.14.128/27	10.0.14.129 – 10.0.14.158	10.0.14.159
54	10.0.14.160/27	10.0.14.161 – 10.0.14.190	10.0.14.191
55	10.0.14.192/27	10.0.14.193 – 10.0.14.222	10.0.14.223
56	10.0.14.224/27	10.0.14.225 – 10.0.14.254	10.0.14.255
57	10.0.15.0/27	10.0.15.1 – 10.0.15.30	10.0.15.31
58	10.0.15.32/27	10.0.15.33 – 10.0.15.62	10.0.15.63
59	10.0.15.64/27	10.0.15.65 – 10.0.15.94	10.0.15.95
60	10.0.15.96/27	10.0.15.97 – 10.0.15.126	10.0.15.127
61	10.0.15.128/27	10.0.15.129 – 10.0.15.158	10.0.15.159
62	10.0.15.160/27	10.0.15.161 – 10.0.15.190	10.0.15.191
63	10.0.15.192/27	10.0.15.193 – 10.0.15.222	10.0.15.223
64	10.0.15.224/27	10.0.15.225 – 10.0.15.254	10.0.15.255

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 →