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)10.2.72.0/21

network10.2.72.0/21

broadcast10.2.79.255

first host10.2.72.1

last host10.2.79.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classA

ipcalc 10.2.72.0/21

address00001010.00000010.01001000.00000000

subnet mask11111111.11111111.11111000.00000000

network00001010.00000010.01001000.00000000

broadcast00001010.00000010.01001111.11111111

green = network part, grey = host part

hex0x0a024800

decimal167921664

reverse dns0.72.2.10.in-addr.arpa

ipv4-mapped::ffff:a02:4800

/21 split into /27 · 64 subnets

close ×

#	network	host range	broadcast
1	10.2.72.0/27	10.2.72.1 – 10.2.72.30	10.2.72.31
2	10.2.72.32/27	10.2.72.33 – 10.2.72.62	10.2.72.63
3	10.2.72.64/27	10.2.72.65 – 10.2.72.94	10.2.72.95
4	10.2.72.96/27	10.2.72.97 – 10.2.72.126	10.2.72.127
5	10.2.72.128/27	10.2.72.129 – 10.2.72.158	10.2.72.159
6	10.2.72.160/27	10.2.72.161 – 10.2.72.190	10.2.72.191
7	10.2.72.192/27	10.2.72.193 – 10.2.72.222	10.2.72.223
8	10.2.72.224/27	10.2.72.225 – 10.2.72.254	10.2.72.255
9	10.2.73.0/27	10.2.73.1 – 10.2.73.30	10.2.73.31
10	10.2.73.32/27	10.2.73.33 – 10.2.73.62	10.2.73.63
11	10.2.73.64/27	10.2.73.65 – 10.2.73.94	10.2.73.95
12	10.2.73.96/27	10.2.73.97 – 10.2.73.126	10.2.73.127
13	10.2.73.128/27	10.2.73.129 – 10.2.73.158	10.2.73.159
14	10.2.73.160/27	10.2.73.161 – 10.2.73.190	10.2.73.191
15	10.2.73.192/27	10.2.73.193 – 10.2.73.222	10.2.73.223
16	10.2.73.224/27	10.2.73.225 – 10.2.73.254	10.2.73.255
17	10.2.74.0/27	10.2.74.1 – 10.2.74.30	10.2.74.31
18	10.2.74.32/27	10.2.74.33 – 10.2.74.62	10.2.74.63
19	10.2.74.64/27	10.2.74.65 – 10.2.74.94	10.2.74.95
20	10.2.74.96/27	10.2.74.97 – 10.2.74.126	10.2.74.127
21	10.2.74.128/27	10.2.74.129 – 10.2.74.158	10.2.74.159
22	10.2.74.160/27	10.2.74.161 – 10.2.74.190	10.2.74.191
23	10.2.74.192/27	10.2.74.193 – 10.2.74.222	10.2.74.223
24	10.2.74.224/27	10.2.74.225 – 10.2.74.254	10.2.74.255
25	10.2.75.0/27	10.2.75.1 – 10.2.75.30	10.2.75.31
26	10.2.75.32/27	10.2.75.33 – 10.2.75.62	10.2.75.63
27	10.2.75.64/27	10.2.75.65 – 10.2.75.94	10.2.75.95
28	10.2.75.96/27	10.2.75.97 – 10.2.75.126	10.2.75.127
29	10.2.75.128/27	10.2.75.129 – 10.2.75.158	10.2.75.159
30	10.2.75.160/27	10.2.75.161 – 10.2.75.190	10.2.75.191
31	10.2.75.192/27	10.2.75.193 – 10.2.75.222	10.2.75.223
32	10.2.75.224/27	10.2.75.225 – 10.2.75.254	10.2.75.255
33	10.2.76.0/27	10.2.76.1 – 10.2.76.30	10.2.76.31
34	10.2.76.32/27	10.2.76.33 – 10.2.76.62	10.2.76.63
35	10.2.76.64/27	10.2.76.65 – 10.2.76.94	10.2.76.95
36	10.2.76.96/27	10.2.76.97 – 10.2.76.126	10.2.76.127
37	10.2.76.128/27	10.2.76.129 – 10.2.76.158	10.2.76.159
38	10.2.76.160/27	10.2.76.161 – 10.2.76.190	10.2.76.191
39	10.2.76.192/27	10.2.76.193 – 10.2.76.222	10.2.76.223
40	10.2.76.224/27	10.2.76.225 – 10.2.76.254	10.2.76.255
41	10.2.77.0/27	10.2.77.1 – 10.2.77.30	10.2.77.31
42	10.2.77.32/27	10.2.77.33 – 10.2.77.62	10.2.77.63
43	10.2.77.64/27	10.2.77.65 – 10.2.77.94	10.2.77.95
44	10.2.77.96/27	10.2.77.97 – 10.2.77.126	10.2.77.127
45	10.2.77.128/27	10.2.77.129 – 10.2.77.158	10.2.77.159
46	10.2.77.160/27	10.2.77.161 – 10.2.77.190	10.2.77.191
47	10.2.77.192/27	10.2.77.193 – 10.2.77.222	10.2.77.223
48	10.2.77.224/27	10.2.77.225 – 10.2.77.254	10.2.77.255
49	10.2.78.0/27	10.2.78.1 – 10.2.78.30	10.2.78.31
50	10.2.78.32/27	10.2.78.33 – 10.2.78.62	10.2.78.63
51	10.2.78.64/27	10.2.78.65 – 10.2.78.94	10.2.78.95
52	10.2.78.96/27	10.2.78.97 – 10.2.78.126	10.2.78.127
53	10.2.78.128/27	10.2.78.129 – 10.2.78.158	10.2.78.159
54	10.2.78.160/27	10.2.78.161 – 10.2.78.190	10.2.78.191
55	10.2.78.192/27	10.2.78.193 – 10.2.78.222	10.2.78.223
56	10.2.78.224/27	10.2.78.225 – 10.2.78.254	10.2.78.255
57	10.2.79.0/27	10.2.79.1 – 10.2.79.30	10.2.79.31
58	10.2.79.32/27	10.2.79.33 – 10.2.79.62	10.2.79.63
59	10.2.79.64/27	10.2.79.65 – 10.2.79.94	10.2.79.95
60	10.2.79.96/27	10.2.79.97 – 10.2.79.126	10.2.79.127
61	10.2.79.128/27	10.2.79.129 – 10.2.79.158	10.2.79.159
62	10.2.79.160/27	10.2.79.161 – 10.2.79.190	10.2.79.191
63	10.2.79.192/27	10.2.79.193 – 10.2.79.222	10.2.79.223
64	10.2.79.224/27	10.2.79.225 – 10.2.79.254	10.2.79.255

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 →