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)10.167.40.0/21

network10.167.40.0/21

broadcast10.167.47.255

first host10.167.40.1

last host10.167.47.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classA

ipcalc 10.167.40.0/21

address00001010.10100111.00101000.00000000

subnet mask11111111.11111111.11111000.00000000

network00001010.10100111.00101000.00000000

broadcast00001010.10100111.00101111.11111111

green = network part, grey = host part

hex0x0aa72800

decimal178726912

reverse dns0.40.167.10.in-addr.arpa

ipv4-mapped::ffff:aa7:2800

/21 split into /27 · 64 subnets

close ×

#	network	host range	broadcast
1	10.167.40.0/27	10.167.40.1 – 10.167.40.30	10.167.40.31
2	10.167.40.32/27	10.167.40.33 – 10.167.40.62	10.167.40.63
3	10.167.40.64/27	10.167.40.65 – 10.167.40.94	10.167.40.95
4	10.167.40.96/27	10.167.40.97 – 10.167.40.126	10.167.40.127
5	10.167.40.128/27	10.167.40.129 – 10.167.40.158	10.167.40.159
6	10.167.40.160/27	10.167.40.161 – 10.167.40.190	10.167.40.191
7	10.167.40.192/27	10.167.40.193 – 10.167.40.222	10.167.40.223
8	10.167.40.224/27	10.167.40.225 – 10.167.40.254	10.167.40.255
9	10.167.41.0/27	10.167.41.1 – 10.167.41.30	10.167.41.31
10	10.167.41.32/27	10.167.41.33 – 10.167.41.62	10.167.41.63
11	10.167.41.64/27	10.167.41.65 – 10.167.41.94	10.167.41.95
12	10.167.41.96/27	10.167.41.97 – 10.167.41.126	10.167.41.127
13	10.167.41.128/27	10.167.41.129 – 10.167.41.158	10.167.41.159
14	10.167.41.160/27	10.167.41.161 – 10.167.41.190	10.167.41.191
15	10.167.41.192/27	10.167.41.193 – 10.167.41.222	10.167.41.223
16	10.167.41.224/27	10.167.41.225 – 10.167.41.254	10.167.41.255
17	10.167.42.0/27	10.167.42.1 – 10.167.42.30	10.167.42.31
18	10.167.42.32/27	10.167.42.33 – 10.167.42.62	10.167.42.63
19	10.167.42.64/27	10.167.42.65 – 10.167.42.94	10.167.42.95
20	10.167.42.96/27	10.167.42.97 – 10.167.42.126	10.167.42.127
21	10.167.42.128/27	10.167.42.129 – 10.167.42.158	10.167.42.159
22	10.167.42.160/27	10.167.42.161 – 10.167.42.190	10.167.42.191
23	10.167.42.192/27	10.167.42.193 – 10.167.42.222	10.167.42.223
24	10.167.42.224/27	10.167.42.225 – 10.167.42.254	10.167.42.255
25	10.167.43.0/27	10.167.43.1 – 10.167.43.30	10.167.43.31
26	10.167.43.32/27	10.167.43.33 – 10.167.43.62	10.167.43.63
27	10.167.43.64/27	10.167.43.65 – 10.167.43.94	10.167.43.95
28	10.167.43.96/27	10.167.43.97 – 10.167.43.126	10.167.43.127
29	10.167.43.128/27	10.167.43.129 – 10.167.43.158	10.167.43.159
30	10.167.43.160/27	10.167.43.161 – 10.167.43.190	10.167.43.191
31	10.167.43.192/27	10.167.43.193 – 10.167.43.222	10.167.43.223
32	10.167.43.224/27	10.167.43.225 – 10.167.43.254	10.167.43.255
33	10.167.44.0/27	10.167.44.1 – 10.167.44.30	10.167.44.31
34	10.167.44.32/27	10.167.44.33 – 10.167.44.62	10.167.44.63
35	10.167.44.64/27	10.167.44.65 – 10.167.44.94	10.167.44.95
36	10.167.44.96/27	10.167.44.97 – 10.167.44.126	10.167.44.127
37	10.167.44.128/27	10.167.44.129 – 10.167.44.158	10.167.44.159
38	10.167.44.160/27	10.167.44.161 – 10.167.44.190	10.167.44.191
39	10.167.44.192/27	10.167.44.193 – 10.167.44.222	10.167.44.223
40	10.167.44.224/27	10.167.44.225 – 10.167.44.254	10.167.44.255
41	10.167.45.0/27	10.167.45.1 – 10.167.45.30	10.167.45.31
42	10.167.45.32/27	10.167.45.33 – 10.167.45.62	10.167.45.63
43	10.167.45.64/27	10.167.45.65 – 10.167.45.94	10.167.45.95
44	10.167.45.96/27	10.167.45.97 – 10.167.45.126	10.167.45.127
45	10.167.45.128/27	10.167.45.129 – 10.167.45.158	10.167.45.159
46	10.167.45.160/27	10.167.45.161 – 10.167.45.190	10.167.45.191
47	10.167.45.192/27	10.167.45.193 – 10.167.45.222	10.167.45.223
48	10.167.45.224/27	10.167.45.225 – 10.167.45.254	10.167.45.255
49	10.167.46.0/27	10.167.46.1 – 10.167.46.30	10.167.46.31
50	10.167.46.32/27	10.167.46.33 – 10.167.46.62	10.167.46.63
51	10.167.46.64/27	10.167.46.65 – 10.167.46.94	10.167.46.95
52	10.167.46.96/27	10.167.46.97 – 10.167.46.126	10.167.46.127
53	10.167.46.128/27	10.167.46.129 – 10.167.46.158	10.167.46.159
54	10.167.46.160/27	10.167.46.161 – 10.167.46.190	10.167.46.191
55	10.167.46.192/27	10.167.46.193 – 10.167.46.222	10.167.46.223
56	10.167.46.224/27	10.167.46.225 – 10.167.46.254	10.167.46.255
57	10.167.47.0/27	10.167.47.1 – 10.167.47.30	10.167.47.31
58	10.167.47.32/27	10.167.47.33 – 10.167.47.62	10.167.47.63
59	10.167.47.64/27	10.167.47.65 – 10.167.47.94	10.167.47.95
60	10.167.47.96/27	10.167.47.97 – 10.167.47.126	10.167.47.127
61	10.167.47.128/27	10.167.47.129 – 10.167.47.158	10.167.47.159
62	10.167.47.160/27	10.167.47.161 – 10.167.47.190	10.167.47.191
63	10.167.47.192/27	10.167.47.193 – 10.167.47.222	10.167.47.223
64	10.167.47.224/27	10.167.47.225 – 10.167.47.254	10.167.47.255

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 →