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)10.5.240.0/21

network10.5.240.0/21

broadcast10.5.247.255

first host10.5.240.1

last host10.5.247.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classA

ipcalc 10.5.240.0/21

address00001010.00000101.11110000.00000000

subnet mask11111111.11111111.11111000.00000000

network00001010.00000101.11110000.00000000

broadcast00001010.00000101.11110111.11111111

green = network part, grey = host part

hex0x0a05f000

decimal168161280

reverse dns0.240.5.10.in-addr.arpa

ipv4-mapped::ffff:a05:f000

/21 split into /27 · 64 subnets

close ×

#	network	host range	broadcast
1	10.5.240.0/27	10.5.240.1 – 10.5.240.30	10.5.240.31
2	10.5.240.32/27	10.5.240.33 – 10.5.240.62	10.5.240.63
3	10.5.240.64/27	10.5.240.65 – 10.5.240.94	10.5.240.95
4	10.5.240.96/27	10.5.240.97 – 10.5.240.126	10.5.240.127
5	10.5.240.128/27	10.5.240.129 – 10.5.240.158	10.5.240.159
6	10.5.240.160/27	10.5.240.161 – 10.5.240.190	10.5.240.191
7	10.5.240.192/27	10.5.240.193 – 10.5.240.222	10.5.240.223
8	10.5.240.224/27	10.5.240.225 – 10.5.240.254	10.5.240.255
9	10.5.241.0/27	10.5.241.1 – 10.5.241.30	10.5.241.31
10	10.5.241.32/27	10.5.241.33 – 10.5.241.62	10.5.241.63
11	10.5.241.64/27	10.5.241.65 – 10.5.241.94	10.5.241.95
12	10.5.241.96/27	10.5.241.97 – 10.5.241.126	10.5.241.127
13	10.5.241.128/27	10.5.241.129 – 10.5.241.158	10.5.241.159
14	10.5.241.160/27	10.5.241.161 – 10.5.241.190	10.5.241.191
15	10.5.241.192/27	10.5.241.193 – 10.5.241.222	10.5.241.223
16	10.5.241.224/27	10.5.241.225 – 10.5.241.254	10.5.241.255
17	10.5.242.0/27	10.5.242.1 – 10.5.242.30	10.5.242.31
18	10.5.242.32/27	10.5.242.33 – 10.5.242.62	10.5.242.63
19	10.5.242.64/27	10.5.242.65 – 10.5.242.94	10.5.242.95
20	10.5.242.96/27	10.5.242.97 – 10.5.242.126	10.5.242.127
21	10.5.242.128/27	10.5.242.129 – 10.5.242.158	10.5.242.159
22	10.5.242.160/27	10.5.242.161 – 10.5.242.190	10.5.242.191
23	10.5.242.192/27	10.5.242.193 – 10.5.242.222	10.5.242.223
24	10.5.242.224/27	10.5.242.225 – 10.5.242.254	10.5.242.255
25	10.5.243.0/27	10.5.243.1 – 10.5.243.30	10.5.243.31
26	10.5.243.32/27	10.5.243.33 – 10.5.243.62	10.5.243.63
27	10.5.243.64/27	10.5.243.65 – 10.5.243.94	10.5.243.95
28	10.5.243.96/27	10.5.243.97 – 10.5.243.126	10.5.243.127
29	10.5.243.128/27	10.5.243.129 – 10.5.243.158	10.5.243.159
30	10.5.243.160/27	10.5.243.161 – 10.5.243.190	10.5.243.191
31	10.5.243.192/27	10.5.243.193 – 10.5.243.222	10.5.243.223
32	10.5.243.224/27	10.5.243.225 – 10.5.243.254	10.5.243.255
33	10.5.244.0/27	10.5.244.1 – 10.5.244.30	10.5.244.31
34	10.5.244.32/27	10.5.244.33 – 10.5.244.62	10.5.244.63
35	10.5.244.64/27	10.5.244.65 – 10.5.244.94	10.5.244.95
36	10.5.244.96/27	10.5.244.97 – 10.5.244.126	10.5.244.127
37	10.5.244.128/27	10.5.244.129 – 10.5.244.158	10.5.244.159
38	10.5.244.160/27	10.5.244.161 – 10.5.244.190	10.5.244.191
39	10.5.244.192/27	10.5.244.193 – 10.5.244.222	10.5.244.223
40	10.5.244.224/27	10.5.244.225 – 10.5.244.254	10.5.244.255
41	10.5.245.0/27	10.5.245.1 – 10.5.245.30	10.5.245.31
42	10.5.245.32/27	10.5.245.33 – 10.5.245.62	10.5.245.63
43	10.5.245.64/27	10.5.245.65 – 10.5.245.94	10.5.245.95
44	10.5.245.96/27	10.5.245.97 – 10.5.245.126	10.5.245.127
45	10.5.245.128/27	10.5.245.129 – 10.5.245.158	10.5.245.159
46	10.5.245.160/27	10.5.245.161 – 10.5.245.190	10.5.245.191
47	10.5.245.192/27	10.5.245.193 – 10.5.245.222	10.5.245.223
48	10.5.245.224/27	10.5.245.225 – 10.5.245.254	10.5.245.255
49	10.5.246.0/27	10.5.246.1 – 10.5.246.30	10.5.246.31
50	10.5.246.32/27	10.5.246.33 – 10.5.246.62	10.5.246.63
51	10.5.246.64/27	10.5.246.65 – 10.5.246.94	10.5.246.95
52	10.5.246.96/27	10.5.246.97 – 10.5.246.126	10.5.246.127
53	10.5.246.128/27	10.5.246.129 – 10.5.246.158	10.5.246.159
54	10.5.246.160/27	10.5.246.161 – 10.5.246.190	10.5.246.191
55	10.5.246.192/27	10.5.246.193 – 10.5.246.222	10.5.246.223
56	10.5.246.224/27	10.5.246.225 – 10.5.246.254	10.5.246.255
57	10.5.247.0/27	10.5.247.1 – 10.5.247.30	10.5.247.31
58	10.5.247.32/27	10.5.247.33 – 10.5.247.62	10.5.247.63
59	10.5.247.64/27	10.5.247.65 – 10.5.247.94	10.5.247.95
60	10.5.247.96/27	10.5.247.97 – 10.5.247.126	10.5.247.127
61	10.5.247.128/27	10.5.247.129 – 10.5.247.158	10.5.247.159
62	10.5.247.160/27	10.5.247.161 – 10.5.247.190	10.5.247.191
63	10.5.247.192/27	10.5.247.193 – 10.5.247.222	10.5.247.223
64	10.5.247.224/27	10.5.247.225 – 10.5.247.254	10.5.247.255

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 →