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)172.16.0.0/21

network172.16.0.0/21

broadcast172.16.7.255

first host172.16.0.1

last host172.16.7.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classB

ipcalc 172.16.0.0/21

address10101100.00010000.00000000.00000000

subnet mask11111111.11111111.11111000.00000000

network10101100.00010000.00000000.00000000

broadcast10101100.00010000.00000111.11111111

green = network part, grey = host part

hex0xac100000

decimal2886729728

reverse dns0.0.16.172.in-addr.arpa

ipv4-mapped::ffff:ac10:0

/21 split into /27 · 64 subnets

close ×

#	network	host range	broadcast
1	172.16.0.0/27	172.16.0.1 – 172.16.0.30	172.16.0.31
2	172.16.0.32/27	172.16.0.33 – 172.16.0.62	172.16.0.63
3	172.16.0.64/27	172.16.0.65 – 172.16.0.94	172.16.0.95
4	172.16.0.96/27	172.16.0.97 – 172.16.0.126	172.16.0.127
5	172.16.0.128/27	172.16.0.129 – 172.16.0.158	172.16.0.159
6	172.16.0.160/27	172.16.0.161 – 172.16.0.190	172.16.0.191
7	172.16.0.192/27	172.16.0.193 – 172.16.0.222	172.16.0.223
8	172.16.0.224/27	172.16.0.225 – 172.16.0.254	172.16.0.255
9	172.16.1.0/27	172.16.1.1 – 172.16.1.30	172.16.1.31
10	172.16.1.32/27	172.16.1.33 – 172.16.1.62	172.16.1.63
11	172.16.1.64/27	172.16.1.65 – 172.16.1.94	172.16.1.95
12	172.16.1.96/27	172.16.1.97 – 172.16.1.126	172.16.1.127
13	172.16.1.128/27	172.16.1.129 – 172.16.1.158	172.16.1.159
14	172.16.1.160/27	172.16.1.161 – 172.16.1.190	172.16.1.191
15	172.16.1.192/27	172.16.1.193 – 172.16.1.222	172.16.1.223
16	172.16.1.224/27	172.16.1.225 – 172.16.1.254	172.16.1.255
17	172.16.2.0/27	172.16.2.1 – 172.16.2.30	172.16.2.31
18	172.16.2.32/27	172.16.2.33 – 172.16.2.62	172.16.2.63
19	172.16.2.64/27	172.16.2.65 – 172.16.2.94	172.16.2.95
20	172.16.2.96/27	172.16.2.97 – 172.16.2.126	172.16.2.127
21	172.16.2.128/27	172.16.2.129 – 172.16.2.158	172.16.2.159
22	172.16.2.160/27	172.16.2.161 – 172.16.2.190	172.16.2.191
23	172.16.2.192/27	172.16.2.193 – 172.16.2.222	172.16.2.223
24	172.16.2.224/27	172.16.2.225 – 172.16.2.254	172.16.2.255
25	172.16.3.0/27	172.16.3.1 – 172.16.3.30	172.16.3.31
26	172.16.3.32/27	172.16.3.33 – 172.16.3.62	172.16.3.63
27	172.16.3.64/27	172.16.3.65 – 172.16.3.94	172.16.3.95
28	172.16.3.96/27	172.16.3.97 – 172.16.3.126	172.16.3.127
29	172.16.3.128/27	172.16.3.129 – 172.16.3.158	172.16.3.159
30	172.16.3.160/27	172.16.3.161 – 172.16.3.190	172.16.3.191
31	172.16.3.192/27	172.16.3.193 – 172.16.3.222	172.16.3.223
32	172.16.3.224/27	172.16.3.225 – 172.16.3.254	172.16.3.255
33	172.16.4.0/27	172.16.4.1 – 172.16.4.30	172.16.4.31
34	172.16.4.32/27	172.16.4.33 – 172.16.4.62	172.16.4.63
35	172.16.4.64/27	172.16.4.65 – 172.16.4.94	172.16.4.95
36	172.16.4.96/27	172.16.4.97 – 172.16.4.126	172.16.4.127
37	172.16.4.128/27	172.16.4.129 – 172.16.4.158	172.16.4.159
38	172.16.4.160/27	172.16.4.161 – 172.16.4.190	172.16.4.191
39	172.16.4.192/27	172.16.4.193 – 172.16.4.222	172.16.4.223
40	172.16.4.224/27	172.16.4.225 – 172.16.4.254	172.16.4.255
41	172.16.5.0/27	172.16.5.1 – 172.16.5.30	172.16.5.31
42	172.16.5.32/27	172.16.5.33 – 172.16.5.62	172.16.5.63
43	172.16.5.64/27	172.16.5.65 – 172.16.5.94	172.16.5.95
44	172.16.5.96/27	172.16.5.97 – 172.16.5.126	172.16.5.127
45	172.16.5.128/27	172.16.5.129 – 172.16.5.158	172.16.5.159
46	172.16.5.160/27	172.16.5.161 – 172.16.5.190	172.16.5.191
47	172.16.5.192/27	172.16.5.193 – 172.16.5.222	172.16.5.223
48	172.16.5.224/27	172.16.5.225 – 172.16.5.254	172.16.5.255
49	172.16.6.0/27	172.16.6.1 – 172.16.6.30	172.16.6.31
50	172.16.6.32/27	172.16.6.33 – 172.16.6.62	172.16.6.63
51	172.16.6.64/27	172.16.6.65 – 172.16.6.94	172.16.6.95
52	172.16.6.96/27	172.16.6.97 – 172.16.6.126	172.16.6.127
53	172.16.6.128/27	172.16.6.129 – 172.16.6.158	172.16.6.159
54	172.16.6.160/27	172.16.6.161 – 172.16.6.190	172.16.6.191
55	172.16.6.192/27	172.16.6.193 – 172.16.6.222	172.16.6.223
56	172.16.6.224/27	172.16.6.225 – 172.16.6.254	172.16.6.255
57	172.16.7.0/27	172.16.7.1 – 172.16.7.30	172.16.7.31
58	172.16.7.32/27	172.16.7.33 – 172.16.7.62	172.16.7.63
59	172.16.7.64/27	172.16.7.65 – 172.16.7.94	172.16.7.95
60	172.16.7.96/27	172.16.7.97 – 172.16.7.126	172.16.7.127
61	172.16.7.128/27	172.16.7.129 – 172.16.7.158	172.16.7.159
62	172.16.7.160/27	172.16.7.161 – 172.16.7.190	172.16.7.191
63	172.16.7.192/27	172.16.7.193 – 172.16.7.222	172.16.7.223
64	172.16.7.224/27	172.16.7.225 – 172.16.7.254	172.16.7.255

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 →