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)10.3.120.0/21

network10.3.120.0/21

broadcast10.3.127.255

first host10.3.120.1

last host10.3.127.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classA

ipcalc 10.3.120.0/21

address00001010.00000011.01111000.00000000

subnet mask11111111.11111111.11111000.00000000

network00001010.00000011.01111000.00000000

broadcast00001010.00000011.01111111.11111111

green = network part, grey = host part

hex0x0a037800

decimal167999488

reverse dns0.120.3.10.in-addr.arpa

ipv4-mapped::ffff:a03:7800

/21 split into /27 · 64 subnets

close ×

#	network	host range	broadcast
1	10.3.120.0/27	10.3.120.1 – 10.3.120.30	10.3.120.31
2	10.3.120.32/27	10.3.120.33 – 10.3.120.62	10.3.120.63
3	10.3.120.64/27	10.3.120.65 – 10.3.120.94	10.3.120.95
4	10.3.120.96/27	10.3.120.97 – 10.3.120.126	10.3.120.127
5	10.3.120.128/27	10.3.120.129 – 10.3.120.158	10.3.120.159
6	10.3.120.160/27	10.3.120.161 – 10.3.120.190	10.3.120.191
7	10.3.120.192/27	10.3.120.193 – 10.3.120.222	10.3.120.223
8	10.3.120.224/27	10.3.120.225 – 10.3.120.254	10.3.120.255
9	10.3.121.0/27	10.3.121.1 – 10.3.121.30	10.3.121.31
10	10.3.121.32/27	10.3.121.33 – 10.3.121.62	10.3.121.63
11	10.3.121.64/27	10.3.121.65 – 10.3.121.94	10.3.121.95
12	10.3.121.96/27	10.3.121.97 – 10.3.121.126	10.3.121.127
13	10.3.121.128/27	10.3.121.129 – 10.3.121.158	10.3.121.159
14	10.3.121.160/27	10.3.121.161 – 10.3.121.190	10.3.121.191
15	10.3.121.192/27	10.3.121.193 – 10.3.121.222	10.3.121.223
16	10.3.121.224/27	10.3.121.225 – 10.3.121.254	10.3.121.255
17	10.3.122.0/27	10.3.122.1 – 10.3.122.30	10.3.122.31
18	10.3.122.32/27	10.3.122.33 – 10.3.122.62	10.3.122.63
19	10.3.122.64/27	10.3.122.65 – 10.3.122.94	10.3.122.95
20	10.3.122.96/27	10.3.122.97 – 10.3.122.126	10.3.122.127
21	10.3.122.128/27	10.3.122.129 – 10.3.122.158	10.3.122.159
22	10.3.122.160/27	10.3.122.161 – 10.3.122.190	10.3.122.191
23	10.3.122.192/27	10.3.122.193 – 10.3.122.222	10.3.122.223
24	10.3.122.224/27	10.3.122.225 – 10.3.122.254	10.3.122.255
25	10.3.123.0/27	10.3.123.1 – 10.3.123.30	10.3.123.31
26	10.3.123.32/27	10.3.123.33 – 10.3.123.62	10.3.123.63
27	10.3.123.64/27	10.3.123.65 – 10.3.123.94	10.3.123.95
28	10.3.123.96/27	10.3.123.97 – 10.3.123.126	10.3.123.127
29	10.3.123.128/27	10.3.123.129 – 10.3.123.158	10.3.123.159
30	10.3.123.160/27	10.3.123.161 – 10.3.123.190	10.3.123.191
31	10.3.123.192/27	10.3.123.193 – 10.3.123.222	10.3.123.223
32	10.3.123.224/27	10.3.123.225 – 10.3.123.254	10.3.123.255
33	10.3.124.0/27	10.3.124.1 – 10.3.124.30	10.3.124.31
34	10.3.124.32/27	10.3.124.33 – 10.3.124.62	10.3.124.63
35	10.3.124.64/27	10.3.124.65 – 10.3.124.94	10.3.124.95
36	10.3.124.96/27	10.3.124.97 – 10.3.124.126	10.3.124.127
37	10.3.124.128/27	10.3.124.129 – 10.3.124.158	10.3.124.159
38	10.3.124.160/27	10.3.124.161 – 10.3.124.190	10.3.124.191
39	10.3.124.192/27	10.3.124.193 – 10.3.124.222	10.3.124.223
40	10.3.124.224/27	10.3.124.225 – 10.3.124.254	10.3.124.255
41	10.3.125.0/27	10.3.125.1 – 10.3.125.30	10.3.125.31
42	10.3.125.32/27	10.3.125.33 – 10.3.125.62	10.3.125.63
43	10.3.125.64/27	10.3.125.65 – 10.3.125.94	10.3.125.95
44	10.3.125.96/27	10.3.125.97 – 10.3.125.126	10.3.125.127
45	10.3.125.128/27	10.3.125.129 – 10.3.125.158	10.3.125.159
46	10.3.125.160/27	10.3.125.161 – 10.3.125.190	10.3.125.191
47	10.3.125.192/27	10.3.125.193 – 10.3.125.222	10.3.125.223
48	10.3.125.224/27	10.3.125.225 – 10.3.125.254	10.3.125.255
49	10.3.126.0/27	10.3.126.1 – 10.3.126.30	10.3.126.31
50	10.3.126.32/27	10.3.126.33 – 10.3.126.62	10.3.126.63
51	10.3.126.64/27	10.3.126.65 – 10.3.126.94	10.3.126.95
52	10.3.126.96/27	10.3.126.97 – 10.3.126.126	10.3.126.127
53	10.3.126.128/27	10.3.126.129 – 10.3.126.158	10.3.126.159
54	10.3.126.160/27	10.3.126.161 – 10.3.126.190	10.3.126.191
55	10.3.126.192/27	10.3.126.193 – 10.3.126.222	10.3.126.223
56	10.3.126.224/27	10.3.126.225 – 10.3.126.254	10.3.126.255
57	10.3.127.0/27	10.3.127.1 – 10.3.127.30	10.3.127.31
58	10.3.127.32/27	10.3.127.33 – 10.3.127.62	10.3.127.63
59	10.3.127.64/27	10.3.127.65 – 10.3.127.94	10.3.127.95
60	10.3.127.96/27	10.3.127.97 – 10.3.127.126	10.3.127.127
61	10.3.127.128/27	10.3.127.129 – 10.3.127.158	10.3.127.159
62	10.3.127.160/27	10.3.127.161 – 10.3.127.190	10.3.127.191
63	10.3.127.192/27	10.3.127.193 – 10.3.127.222	10.3.127.223
64	10.3.127.224/27	10.3.127.225 – 10.3.127.254	10.3.127.255

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 →