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)10.2.64.0/21

network10.2.64.0/21

broadcast10.2.71.255

first host10.2.64.1

last host10.2.71.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classA

ipcalc 10.2.64.0/21

address00001010.00000010.01000000.00000000

subnet mask11111111.11111111.11111000.00000000

network00001010.00000010.01000000.00000000

broadcast00001010.00000010.01000111.11111111

green = network part, grey = host part

hex0x0a024000

decimal167919616

reverse dns0.64.2.10.in-addr.arpa

ipv4-mapped::ffff:a02:4000

/21 split into /27 · 64 subnets

close ×

#	network	host range	broadcast
1	10.2.64.0/27	10.2.64.1 – 10.2.64.30	10.2.64.31
2	10.2.64.32/27	10.2.64.33 – 10.2.64.62	10.2.64.63
3	10.2.64.64/27	10.2.64.65 – 10.2.64.94	10.2.64.95
4	10.2.64.96/27	10.2.64.97 – 10.2.64.126	10.2.64.127
5	10.2.64.128/27	10.2.64.129 – 10.2.64.158	10.2.64.159
6	10.2.64.160/27	10.2.64.161 – 10.2.64.190	10.2.64.191
7	10.2.64.192/27	10.2.64.193 – 10.2.64.222	10.2.64.223
8	10.2.64.224/27	10.2.64.225 – 10.2.64.254	10.2.64.255
9	10.2.65.0/27	10.2.65.1 – 10.2.65.30	10.2.65.31
10	10.2.65.32/27	10.2.65.33 – 10.2.65.62	10.2.65.63
11	10.2.65.64/27	10.2.65.65 – 10.2.65.94	10.2.65.95
12	10.2.65.96/27	10.2.65.97 – 10.2.65.126	10.2.65.127
13	10.2.65.128/27	10.2.65.129 – 10.2.65.158	10.2.65.159
14	10.2.65.160/27	10.2.65.161 – 10.2.65.190	10.2.65.191
15	10.2.65.192/27	10.2.65.193 – 10.2.65.222	10.2.65.223
16	10.2.65.224/27	10.2.65.225 – 10.2.65.254	10.2.65.255
17	10.2.66.0/27	10.2.66.1 – 10.2.66.30	10.2.66.31
18	10.2.66.32/27	10.2.66.33 – 10.2.66.62	10.2.66.63
19	10.2.66.64/27	10.2.66.65 – 10.2.66.94	10.2.66.95
20	10.2.66.96/27	10.2.66.97 – 10.2.66.126	10.2.66.127
21	10.2.66.128/27	10.2.66.129 – 10.2.66.158	10.2.66.159
22	10.2.66.160/27	10.2.66.161 – 10.2.66.190	10.2.66.191
23	10.2.66.192/27	10.2.66.193 – 10.2.66.222	10.2.66.223
24	10.2.66.224/27	10.2.66.225 – 10.2.66.254	10.2.66.255
25	10.2.67.0/27	10.2.67.1 – 10.2.67.30	10.2.67.31
26	10.2.67.32/27	10.2.67.33 – 10.2.67.62	10.2.67.63
27	10.2.67.64/27	10.2.67.65 – 10.2.67.94	10.2.67.95
28	10.2.67.96/27	10.2.67.97 – 10.2.67.126	10.2.67.127
29	10.2.67.128/27	10.2.67.129 – 10.2.67.158	10.2.67.159
30	10.2.67.160/27	10.2.67.161 – 10.2.67.190	10.2.67.191
31	10.2.67.192/27	10.2.67.193 – 10.2.67.222	10.2.67.223
32	10.2.67.224/27	10.2.67.225 – 10.2.67.254	10.2.67.255
33	10.2.68.0/27	10.2.68.1 – 10.2.68.30	10.2.68.31
34	10.2.68.32/27	10.2.68.33 – 10.2.68.62	10.2.68.63
35	10.2.68.64/27	10.2.68.65 – 10.2.68.94	10.2.68.95
36	10.2.68.96/27	10.2.68.97 – 10.2.68.126	10.2.68.127
37	10.2.68.128/27	10.2.68.129 – 10.2.68.158	10.2.68.159
38	10.2.68.160/27	10.2.68.161 – 10.2.68.190	10.2.68.191
39	10.2.68.192/27	10.2.68.193 – 10.2.68.222	10.2.68.223
40	10.2.68.224/27	10.2.68.225 – 10.2.68.254	10.2.68.255
41	10.2.69.0/27	10.2.69.1 – 10.2.69.30	10.2.69.31
42	10.2.69.32/27	10.2.69.33 – 10.2.69.62	10.2.69.63
43	10.2.69.64/27	10.2.69.65 – 10.2.69.94	10.2.69.95
44	10.2.69.96/27	10.2.69.97 – 10.2.69.126	10.2.69.127
45	10.2.69.128/27	10.2.69.129 – 10.2.69.158	10.2.69.159
46	10.2.69.160/27	10.2.69.161 – 10.2.69.190	10.2.69.191
47	10.2.69.192/27	10.2.69.193 – 10.2.69.222	10.2.69.223
48	10.2.69.224/27	10.2.69.225 – 10.2.69.254	10.2.69.255
49	10.2.70.0/27	10.2.70.1 – 10.2.70.30	10.2.70.31
50	10.2.70.32/27	10.2.70.33 – 10.2.70.62	10.2.70.63
51	10.2.70.64/27	10.2.70.65 – 10.2.70.94	10.2.70.95
52	10.2.70.96/27	10.2.70.97 – 10.2.70.126	10.2.70.127
53	10.2.70.128/27	10.2.70.129 – 10.2.70.158	10.2.70.159
54	10.2.70.160/27	10.2.70.161 – 10.2.70.190	10.2.70.191
55	10.2.70.192/27	10.2.70.193 – 10.2.70.222	10.2.70.223
56	10.2.70.224/27	10.2.70.225 – 10.2.70.254	10.2.70.255
57	10.2.71.0/27	10.2.71.1 – 10.2.71.30	10.2.71.31
58	10.2.71.32/27	10.2.71.33 – 10.2.71.62	10.2.71.63
59	10.2.71.64/27	10.2.71.65 – 10.2.71.94	10.2.71.95
60	10.2.71.96/27	10.2.71.97 – 10.2.71.126	10.2.71.127
61	10.2.71.128/27	10.2.71.129 – 10.2.71.158	10.2.71.159
62	10.2.71.160/27	10.2.71.161 – 10.2.71.190	10.2.71.191
63	10.2.71.192/27	10.2.71.193 – 10.2.71.222	10.2.71.223
64	10.2.71.224/27	10.2.71.225 – 10.2.71.254	10.2.71.255

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 →