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)10.3.40.0/21

network10.3.40.0/21

broadcast10.3.47.255

first host10.3.40.1

last host10.3.47.254

subnet mask255.255.248.0

wildcard0.0.7.255

addresses2,048

usable hosts2,046

classA

ipcalc 10.3.40.0/21

address00001010.00000011.00101000.00000000

subnet mask11111111.11111111.11111000.00000000

network00001010.00000011.00101000.00000000

broadcast00001010.00000011.00101111.11111111

green = network part, grey = host part

hex0x0a032800

decimal167979008

reverse dns0.40.3.10.in-addr.arpa

ipv4-mapped::ffff:a03:2800

/21 split into /28 · 128 subnets

close ×

#	network	host range	broadcast
1	10.3.40.0/28	10.3.40.1 – 10.3.40.14	10.3.40.15
2	10.3.40.16/28	10.3.40.17 – 10.3.40.30	10.3.40.31
3	10.3.40.32/28	10.3.40.33 – 10.3.40.46	10.3.40.47
4	10.3.40.48/28	10.3.40.49 – 10.3.40.62	10.3.40.63
5	10.3.40.64/28	10.3.40.65 – 10.3.40.78	10.3.40.79
6	10.3.40.80/28	10.3.40.81 – 10.3.40.94	10.3.40.95
7	10.3.40.96/28	10.3.40.97 – 10.3.40.110	10.3.40.111
8	10.3.40.112/28	10.3.40.113 – 10.3.40.126	10.3.40.127
9	10.3.40.128/28	10.3.40.129 – 10.3.40.142	10.3.40.143
10	10.3.40.144/28	10.3.40.145 – 10.3.40.158	10.3.40.159
11	10.3.40.160/28	10.3.40.161 – 10.3.40.174	10.3.40.175
12	10.3.40.176/28	10.3.40.177 – 10.3.40.190	10.3.40.191
13	10.3.40.192/28	10.3.40.193 – 10.3.40.206	10.3.40.207
14	10.3.40.208/28	10.3.40.209 – 10.3.40.222	10.3.40.223
15	10.3.40.224/28	10.3.40.225 – 10.3.40.238	10.3.40.239
16	10.3.40.240/28	10.3.40.241 – 10.3.40.254	10.3.40.255
17	10.3.41.0/28	10.3.41.1 – 10.3.41.14	10.3.41.15
18	10.3.41.16/28	10.3.41.17 – 10.3.41.30	10.3.41.31
19	10.3.41.32/28	10.3.41.33 – 10.3.41.46	10.3.41.47
20	10.3.41.48/28	10.3.41.49 – 10.3.41.62	10.3.41.63
21	10.3.41.64/28	10.3.41.65 – 10.3.41.78	10.3.41.79
22	10.3.41.80/28	10.3.41.81 – 10.3.41.94	10.3.41.95
23	10.3.41.96/28	10.3.41.97 – 10.3.41.110	10.3.41.111
24	10.3.41.112/28	10.3.41.113 – 10.3.41.126	10.3.41.127
25	10.3.41.128/28	10.3.41.129 – 10.3.41.142	10.3.41.143
26	10.3.41.144/28	10.3.41.145 – 10.3.41.158	10.3.41.159
27	10.3.41.160/28	10.3.41.161 – 10.3.41.174	10.3.41.175
28	10.3.41.176/28	10.3.41.177 – 10.3.41.190	10.3.41.191
29	10.3.41.192/28	10.3.41.193 – 10.3.41.206	10.3.41.207
30	10.3.41.208/28	10.3.41.209 – 10.3.41.222	10.3.41.223
31	10.3.41.224/28	10.3.41.225 – 10.3.41.238	10.3.41.239
32	10.3.41.240/28	10.3.41.241 – 10.3.41.254	10.3.41.255
33	10.3.42.0/28	10.3.42.1 – 10.3.42.14	10.3.42.15
34	10.3.42.16/28	10.3.42.17 – 10.3.42.30	10.3.42.31
35	10.3.42.32/28	10.3.42.33 – 10.3.42.46	10.3.42.47
36	10.3.42.48/28	10.3.42.49 – 10.3.42.62	10.3.42.63
37	10.3.42.64/28	10.3.42.65 – 10.3.42.78	10.3.42.79
38	10.3.42.80/28	10.3.42.81 – 10.3.42.94	10.3.42.95
39	10.3.42.96/28	10.3.42.97 – 10.3.42.110	10.3.42.111
40	10.3.42.112/28	10.3.42.113 – 10.3.42.126	10.3.42.127
41	10.3.42.128/28	10.3.42.129 – 10.3.42.142	10.3.42.143
42	10.3.42.144/28	10.3.42.145 – 10.3.42.158	10.3.42.159
43	10.3.42.160/28	10.3.42.161 – 10.3.42.174	10.3.42.175
44	10.3.42.176/28	10.3.42.177 – 10.3.42.190	10.3.42.191
45	10.3.42.192/28	10.3.42.193 – 10.3.42.206	10.3.42.207
46	10.3.42.208/28	10.3.42.209 – 10.3.42.222	10.3.42.223
47	10.3.42.224/28	10.3.42.225 – 10.3.42.238	10.3.42.239
48	10.3.42.240/28	10.3.42.241 – 10.3.42.254	10.3.42.255
49	10.3.43.0/28	10.3.43.1 – 10.3.43.14	10.3.43.15
50	10.3.43.16/28	10.3.43.17 – 10.3.43.30	10.3.43.31
51	10.3.43.32/28	10.3.43.33 – 10.3.43.46	10.3.43.47
52	10.3.43.48/28	10.3.43.49 – 10.3.43.62	10.3.43.63
53	10.3.43.64/28	10.3.43.65 – 10.3.43.78	10.3.43.79
54	10.3.43.80/28	10.3.43.81 – 10.3.43.94	10.3.43.95
55	10.3.43.96/28	10.3.43.97 – 10.3.43.110	10.3.43.111
56	10.3.43.112/28	10.3.43.113 – 10.3.43.126	10.3.43.127
57	10.3.43.128/28	10.3.43.129 – 10.3.43.142	10.3.43.143
58	10.3.43.144/28	10.3.43.145 – 10.3.43.158	10.3.43.159
59	10.3.43.160/28	10.3.43.161 – 10.3.43.174	10.3.43.175
60	10.3.43.176/28	10.3.43.177 – 10.3.43.190	10.3.43.191
61	10.3.43.192/28	10.3.43.193 – 10.3.43.206	10.3.43.207
62	10.3.43.208/28	10.3.43.209 – 10.3.43.222	10.3.43.223
63	10.3.43.224/28	10.3.43.225 – 10.3.43.238	10.3.43.239
64	10.3.43.240/28	10.3.43.241 – 10.3.43.254	10.3.43.255
65	10.3.44.0/28	10.3.44.1 – 10.3.44.14	10.3.44.15
66	10.3.44.16/28	10.3.44.17 – 10.3.44.30	10.3.44.31
67	10.3.44.32/28	10.3.44.33 – 10.3.44.46	10.3.44.47
68	10.3.44.48/28	10.3.44.49 – 10.3.44.62	10.3.44.63
69	10.3.44.64/28	10.3.44.65 – 10.3.44.78	10.3.44.79
70	10.3.44.80/28	10.3.44.81 – 10.3.44.94	10.3.44.95
71	10.3.44.96/28	10.3.44.97 – 10.3.44.110	10.3.44.111
72	10.3.44.112/28	10.3.44.113 – 10.3.44.126	10.3.44.127
73	10.3.44.128/28	10.3.44.129 – 10.3.44.142	10.3.44.143
74	10.3.44.144/28	10.3.44.145 – 10.3.44.158	10.3.44.159
75	10.3.44.160/28	10.3.44.161 – 10.3.44.174	10.3.44.175
76	10.3.44.176/28	10.3.44.177 – 10.3.44.190	10.3.44.191
77	10.3.44.192/28	10.3.44.193 – 10.3.44.206	10.3.44.207
78	10.3.44.208/28	10.3.44.209 – 10.3.44.222	10.3.44.223
79	10.3.44.224/28	10.3.44.225 – 10.3.44.238	10.3.44.239
80	10.3.44.240/28	10.3.44.241 – 10.3.44.254	10.3.44.255
81	10.3.45.0/28	10.3.45.1 – 10.3.45.14	10.3.45.15
82	10.3.45.16/28	10.3.45.17 – 10.3.45.30	10.3.45.31
83	10.3.45.32/28	10.3.45.33 – 10.3.45.46	10.3.45.47
84	10.3.45.48/28	10.3.45.49 – 10.3.45.62	10.3.45.63
85	10.3.45.64/28	10.3.45.65 – 10.3.45.78	10.3.45.79
86	10.3.45.80/28	10.3.45.81 – 10.3.45.94	10.3.45.95
87	10.3.45.96/28	10.3.45.97 – 10.3.45.110	10.3.45.111
88	10.3.45.112/28	10.3.45.113 – 10.3.45.126	10.3.45.127
89	10.3.45.128/28	10.3.45.129 – 10.3.45.142	10.3.45.143
90	10.3.45.144/28	10.3.45.145 – 10.3.45.158	10.3.45.159
91	10.3.45.160/28	10.3.45.161 – 10.3.45.174	10.3.45.175
92	10.3.45.176/28	10.3.45.177 – 10.3.45.190	10.3.45.191
93	10.3.45.192/28	10.3.45.193 – 10.3.45.206	10.3.45.207
94	10.3.45.208/28	10.3.45.209 – 10.3.45.222	10.3.45.223
95	10.3.45.224/28	10.3.45.225 – 10.3.45.238	10.3.45.239
96	10.3.45.240/28	10.3.45.241 – 10.3.45.254	10.3.45.255
97	10.3.46.0/28	10.3.46.1 – 10.3.46.14	10.3.46.15
98	10.3.46.16/28	10.3.46.17 – 10.3.46.30	10.3.46.31
99	10.3.46.32/28	10.3.46.33 – 10.3.46.46	10.3.46.47
100	10.3.46.48/28	10.3.46.49 – 10.3.46.62	10.3.46.63
101	10.3.46.64/28	10.3.46.65 – 10.3.46.78	10.3.46.79
102	10.3.46.80/28	10.3.46.81 – 10.3.46.94	10.3.46.95
103	10.3.46.96/28	10.3.46.97 – 10.3.46.110	10.3.46.111
104	10.3.46.112/28	10.3.46.113 – 10.3.46.126	10.3.46.127
105	10.3.46.128/28	10.3.46.129 – 10.3.46.142	10.3.46.143
106	10.3.46.144/28	10.3.46.145 – 10.3.46.158	10.3.46.159
107	10.3.46.160/28	10.3.46.161 – 10.3.46.174	10.3.46.175
108	10.3.46.176/28	10.3.46.177 – 10.3.46.190	10.3.46.191
109	10.3.46.192/28	10.3.46.193 – 10.3.46.206	10.3.46.207
110	10.3.46.208/28	10.3.46.209 – 10.3.46.222	10.3.46.223
111	10.3.46.224/28	10.3.46.225 – 10.3.46.238	10.3.46.239
112	10.3.46.240/28	10.3.46.241 – 10.3.46.254	10.3.46.255
113	10.3.47.0/28	10.3.47.1 – 10.3.47.14	10.3.47.15
114	10.3.47.16/28	10.3.47.17 – 10.3.47.30	10.3.47.31
115	10.3.47.32/28	10.3.47.33 – 10.3.47.46	10.3.47.47
116	10.3.47.48/28	10.3.47.49 – 10.3.47.62	10.3.47.63
117	10.3.47.64/28	10.3.47.65 – 10.3.47.78	10.3.47.79
118	10.3.47.80/28	10.3.47.81 – 10.3.47.94	10.3.47.95
119	10.3.47.96/28	10.3.47.97 – 10.3.47.110	10.3.47.111
120	10.3.47.112/28	10.3.47.113 – 10.3.47.126	10.3.47.127
121	10.3.47.128/28	10.3.47.129 – 10.3.47.142	10.3.47.143
122	10.3.47.144/28	10.3.47.145 – 10.3.47.158	10.3.47.159
123	10.3.47.160/28	10.3.47.161 – 10.3.47.174	10.3.47.175
124	10.3.47.176/28	10.3.47.177 – 10.3.47.190	10.3.47.191
125	10.3.47.192/28	10.3.47.193 – 10.3.47.206	10.3.47.207
126	10.3.47.208/28	10.3.47.209 – 10.3.47.222	10.3.47.223
127	10.3.47.224/28	10.3.47.225 – 10.3.47.238	10.3.47.239
128	10.3.47.240/28	10.3.47.241 – 10.3.47.254	10.3.47.255

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 →