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)10.5.16.0/21

network10.5.16.0/21

broadcast10.5.23.255

first host10.5.16.1

last host10.5.23.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classA

ipcalc 10.5.16.0/21

address00001010.00000101.00010000.00000000

subnet mask11111111.11111111.11111000.00000000

network00001010.00000101.00010000.00000000

broadcast00001010.00000101.00010111.11111111

green = network part, grey = host part

hex0x0a051000

decimal168103936

reverse dns0.16.5.10.in-addr.arpa

ipv4-mapped::ffff:a05:1000

/21 split into /26 · 32 subnets

close ×

#	network	host range	broadcast
1	10.5.16.0/26	10.5.16.1 – 10.5.16.62	10.5.16.63
2	10.5.16.64/26	10.5.16.65 – 10.5.16.126	10.5.16.127
3	10.5.16.128/26	10.5.16.129 – 10.5.16.190	10.5.16.191
4	10.5.16.192/26	10.5.16.193 – 10.5.16.254	10.5.16.255
5	10.5.17.0/26	10.5.17.1 – 10.5.17.62	10.5.17.63
6	10.5.17.64/26	10.5.17.65 – 10.5.17.126	10.5.17.127
7	10.5.17.128/26	10.5.17.129 – 10.5.17.190	10.5.17.191
8	10.5.17.192/26	10.5.17.193 – 10.5.17.254	10.5.17.255
9	10.5.18.0/26	10.5.18.1 – 10.5.18.62	10.5.18.63
10	10.5.18.64/26	10.5.18.65 – 10.5.18.126	10.5.18.127
11	10.5.18.128/26	10.5.18.129 – 10.5.18.190	10.5.18.191
12	10.5.18.192/26	10.5.18.193 – 10.5.18.254	10.5.18.255
13	10.5.19.0/26	10.5.19.1 – 10.5.19.62	10.5.19.63
14	10.5.19.64/26	10.5.19.65 – 10.5.19.126	10.5.19.127
15	10.5.19.128/26	10.5.19.129 – 10.5.19.190	10.5.19.191
16	10.5.19.192/26	10.5.19.193 – 10.5.19.254	10.5.19.255
17	10.5.20.0/26	10.5.20.1 – 10.5.20.62	10.5.20.63
18	10.5.20.64/26	10.5.20.65 – 10.5.20.126	10.5.20.127
19	10.5.20.128/26	10.5.20.129 – 10.5.20.190	10.5.20.191
20	10.5.20.192/26	10.5.20.193 – 10.5.20.254	10.5.20.255
21	10.5.21.0/26	10.5.21.1 – 10.5.21.62	10.5.21.63
22	10.5.21.64/26	10.5.21.65 – 10.5.21.126	10.5.21.127
23	10.5.21.128/26	10.5.21.129 – 10.5.21.190	10.5.21.191
24	10.5.21.192/26	10.5.21.193 – 10.5.21.254	10.5.21.255
25	10.5.22.0/26	10.5.22.1 – 10.5.22.62	10.5.22.63
26	10.5.22.64/26	10.5.22.65 – 10.5.22.126	10.5.22.127
27	10.5.22.128/26	10.5.22.129 – 10.5.22.190	10.5.22.191
28	10.5.22.192/26	10.5.22.193 – 10.5.22.254	10.5.22.255
29	10.5.23.0/26	10.5.23.1 – 10.5.23.62	10.5.23.63
30	10.5.23.64/26	10.5.23.65 – 10.5.23.126	10.5.23.127
31	10.5.23.128/26	10.5.23.129 – 10.5.23.190	10.5.23.191
32	10.5.23.192/26	10.5.23.193 – 10.5.23.254	10.5.23.255

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 →