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.
private IP (RFC 1918)10.4.128.0/21
network10.4.128.0/21
broadcast10.4.135.255
first host10.4.128.1
last host10.4.135.254
subnet mask255.255.248.0
wildcard0.0.7.255
addresses2,048
usable hosts2,046
classA
ipcalc 10.4.128.0/21
address00001010.00000100.10000000.00000000
subnet mask11111111.11111111.11111000.00000000
network00001010.00000100.10000000.00000000
broadcast00001010.00000100.10000111.11111111
green = network part, grey = host part
hex0x0a048000
decimal168067072
reverse dns0.128.4.10.in-addr.arpa
ipv4-mapped::ffff:a04:8000
/21 split into /28 · 128 subnets
close ×| # | network | host range | broadcast |
|---|---|---|---|
| 1 | 10.4.128.0/28 | 10.4.128.1 – 10.4.128.14 | 10.4.128.15 |
| 2 | 10.4.128.16/28 | 10.4.128.17 – 10.4.128.30 | 10.4.128.31 |
| 3 | 10.4.128.32/28 | 10.4.128.33 – 10.4.128.46 | 10.4.128.47 |
| 4 | 10.4.128.48/28 | 10.4.128.49 – 10.4.128.62 | 10.4.128.63 |
| 5 | 10.4.128.64/28 | 10.4.128.65 – 10.4.128.78 | 10.4.128.79 |
| 6 | 10.4.128.80/28 | 10.4.128.81 – 10.4.128.94 | 10.4.128.95 |
| 7 | 10.4.128.96/28 | 10.4.128.97 – 10.4.128.110 | 10.4.128.111 |
| 8 | 10.4.128.112/28 | 10.4.128.113 – 10.4.128.126 | 10.4.128.127 |
| 9 | 10.4.128.128/28 | 10.4.128.129 – 10.4.128.142 | 10.4.128.143 |
| 10 | 10.4.128.144/28 | 10.4.128.145 – 10.4.128.158 | 10.4.128.159 |
| 11 | 10.4.128.160/28 | 10.4.128.161 – 10.4.128.174 | 10.4.128.175 |
| 12 | 10.4.128.176/28 | 10.4.128.177 – 10.4.128.190 | 10.4.128.191 |
| 13 | 10.4.128.192/28 | 10.4.128.193 – 10.4.128.206 | 10.4.128.207 |
| 14 | 10.4.128.208/28 | 10.4.128.209 – 10.4.128.222 | 10.4.128.223 |
| 15 | 10.4.128.224/28 | 10.4.128.225 – 10.4.128.238 | 10.4.128.239 |
| 16 | 10.4.128.240/28 | 10.4.128.241 – 10.4.128.254 | 10.4.128.255 |
| 17 | 10.4.129.0/28 | 10.4.129.1 – 10.4.129.14 | 10.4.129.15 |
| 18 | 10.4.129.16/28 | 10.4.129.17 – 10.4.129.30 | 10.4.129.31 |
| 19 | 10.4.129.32/28 | 10.4.129.33 – 10.4.129.46 | 10.4.129.47 |
| 20 | 10.4.129.48/28 | 10.4.129.49 – 10.4.129.62 | 10.4.129.63 |
| 21 | 10.4.129.64/28 | 10.4.129.65 – 10.4.129.78 | 10.4.129.79 |
| 22 | 10.4.129.80/28 | 10.4.129.81 – 10.4.129.94 | 10.4.129.95 |
| 23 | 10.4.129.96/28 | 10.4.129.97 – 10.4.129.110 | 10.4.129.111 |
| 24 | 10.4.129.112/28 | 10.4.129.113 – 10.4.129.126 | 10.4.129.127 |
| 25 | 10.4.129.128/28 | 10.4.129.129 – 10.4.129.142 | 10.4.129.143 |
| 26 | 10.4.129.144/28 | 10.4.129.145 – 10.4.129.158 | 10.4.129.159 |
| 27 | 10.4.129.160/28 | 10.4.129.161 – 10.4.129.174 | 10.4.129.175 |
| 28 | 10.4.129.176/28 | 10.4.129.177 – 10.4.129.190 | 10.4.129.191 |
| 29 | 10.4.129.192/28 | 10.4.129.193 – 10.4.129.206 | 10.4.129.207 |
| 30 | 10.4.129.208/28 | 10.4.129.209 – 10.4.129.222 | 10.4.129.223 |
| 31 | 10.4.129.224/28 | 10.4.129.225 – 10.4.129.238 | 10.4.129.239 |
| 32 | 10.4.129.240/28 | 10.4.129.241 – 10.4.129.254 | 10.4.129.255 |
| 33 | 10.4.130.0/28 | 10.4.130.1 – 10.4.130.14 | 10.4.130.15 |
| 34 | 10.4.130.16/28 | 10.4.130.17 – 10.4.130.30 | 10.4.130.31 |
| 35 | 10.4.130.32/28 | 10.4.130.33 – 10.4.130.46 | 10.4.130.47 |
| 36 | 10.4.130.48/28 | 10.4.130.49 – 10.4.130.62 | 10.4.130.63 |
| 37 | 10.4.130.64/28 | 10.4.130.65 – 10.4.130.78 | 10.4.130.79 |
| 38 | 10.4.130.80/28 | 10.4.130.81 – 10.4.130.94 | 10.4.130.95 |
| 39 | 10.4.130.96/28 | 10.4.130.97 – 10.4.130.110 | 10.4.130.111 |
| 40 | 10.4.130.112/28 | 10.4.130.113 – 10.4.130.126 | 10.4.130.127 |
| 41 | 10.4.130.128/28 | 10.4.130.129 – 10.4.130.142 | 10.4.130.143 |
| 42 | 10.4.130.144/28 | 10.4.130.145 – 10.4.130.158 | 10.4.130.159 |
| 43 | 10.4.130.160/28 | 10.4.130.161 – 10.4.130.174 | 10.4.130.175 |
| 44 | 10.4.130.176/28 | 10.4.130.177 – 10.4.130.190 | 10.4.130.191 |
| 45 | 10.4.130.192/28 | 10.4.130.193 – 10.4.130.206 | 10.4.130.207 |
| 46 | 10.4.130.208/28 | 10.4.130.209 – 10.4.130.222 | 10.4.130.223 |
| 47 | 10.4.130.224/28 | 10.4.130.225 – 10.4.130.238 | 10.4.130.239 |
| 48 | 10.4.130.240/28 | 10.4.130.241 – 10.4.130.254 | 10.4.130.255 |
| 49 | 10.4.131.0/28 | 10.4.131.1 – 10.4.131.14 | 10.4.131.15 |
| 50 | 10.4.131.16/28 | 10.4.131.17 – 10.4.131.30 | 10.4.131.31 |
| 51 | 10.4.131.32/28 | 10.4.131.33 – 10.4.131.46 | 10.4.131.47 |
| 52 | 10.4.131.48/28 | 10.4.131.49 – 10.4.131.62 | 10.4.131.63 |
| 53 | 10.4.131.64/28 | 10.4.131.65 – 10.4.131.78 | 10.4.131.79 |
| 54 | 10.4.131.80/28 | 10.4.131.81 – 10.4.131.94 | 10.4.131.95 |
| 55 | 10.4.131.96/28 | 10.4.131.97 – 10.4.131.110 | 10.4.131.111 |
| 56 | 10.4.131.112/28 | 10.4.131.113 – 10.4.131.126 | 10.4.131.127 |
| 57 | 10.4.131.128/28 | 10.4.131.129 – 10.4.131.142 | 10.4.131.143 |
| 58 | 10.4.131.144/28 | 10.4.131.145 – 10.4.131.158 | 10.4.131.159 |
| 59 | 10.4.131.160/28 | 10.4.131.161 – 10.4.131.174 | 10.4.131.175 |
| 60 | 10.4.131.176/28 | 10.4.131.177 – 10.4.131.190 | 10.4.131.191 |
| 61 | 10.4.131.192/28 | 10.4.131.193 – 10.4.131.206 | 10.4.131.207 |
| 62 | 10.4.131.208/28 | 10.4.131.209 – 10.4.131.222 | 10.4.131.223 |
| 63 | 10.4.131.224/28 | 10.4.131.225 – 10.4.131.238 | 10.4.131.239 |
| 64 | 10.4.131.240/28 | 10.4.131.241 – 10.4.131.254 | 10.4.131.255 |
| 65 | 10.4.132.0/28 | 10.4.132.1 – 10.4.132.14 | 10.4.132.15 |
| 66 | 10.4.132.16/28 | 10.4.132.17 – 10.4.132.30 | 10.4.132.31 |
| 67 | 10.4.132.32/28 | 10.4.132.33 – 10.4.132.46 | 10.4.132.47 |
| 68 | 10.4.132.48/28 | 10.4.132.49 – 10.4.132.62 | 10.4.132.63 |
| 69 | 10.4.132.64/28 | 10.4.132.65 – 10.4.132.78 | 10.4.132.79 |
| 70 | 10.4.132.80/28 | 10.4.132.81 – 10.4.132.94 | 10.4.132.95 |
| 71 | 10.4.132.96/28 | 10.4.132.97 – 10.4.132.110 | 10.4.132.111 |
| 72 | 10.4.132.112/28 | 10.4.132.113 – 10.4.132.126 | 10.4.132.127 |
| 73 | 10.4.132.128/28 | 10.4.132.129 – 10.4.132.142 | 10.4.132.143 |
| 74 | 10.4.132.144/28 | 10.4.132.145 – 10.4.132.158 | 10.4.132.159 |
| 75 | 10.4.132.160/28 | 10.4.132.161 – 10.4.132.174 | 10.4.132.175 |
| 76 | 10.4.132.176/28 | 10.4.132.177 – 10.4.132.190 | 10.4.132.191 |
| 77 | 10.4.132.192/28 | 10.4.132.193 – 10.4.132.206 | 10.4.132.207 |
| 78 | 10.4.132.208/28 | 10.4.132.209 – 10.4.132.222 | 10.4.132.223 |
| 79 | 10.4.132.224/28 | 10.4.132.225 – 10.4.132.238 | 10.4.132.239 |
| 80 | 10.4.132.240/28 | 10.4.132.241 – 10.4.132.254 | 10.4.132.255 |
| 81 | 10.4.133.0/28 | 10.4.133.1 – 10.4.133.14 | 10.4.133.15 |
| 82 | 10.4.133.16/28 | 10.4.133.17 – 10.4.133.30 | 10.4.133.31 |
| 83 | 10.4.133.32/28 | 10.4.133.33 – 10.4.133.46 | 10.4.133.47 |
| 84 | 10.4.133.48/28 | 10.4.133.49 – 10.4.133.62 | 10.4.133.63 |
| 85 | 10.4.133.64/28 | 10.4.133.65 – 10.4.133.78 | 10.4.133.79 |
| 86 | 10.4.133.80/28 | 10.4.133.81 – 10.4.133.94 | 10.4.133.95 |
| 87 | 10.4.133.96/28 | 10.4.133.97 – 10.4.133.110 | 10.4.133.111 |
| 88 | 10.4.133.112/28 | 10.4.133.113 – 10.4.133.126 | 10.4.133.127 |
| 89 | 10.4.133.128/28 | 10.4.133.129 – 10.4.133.142 | 10.4.133.143 |
| 90 | 10.4.133.144/28 | 10.4.133.145 – 10.4.133.158 | 10.4.133.159 |
| 91 | 10.4.133.160/28 | 10.4.133.161 – 10.4.133.174 | 10.4.133.175 |
| 92 | 10.4.133.176/28 | 10.4.133.177 – 10.4.133.190 | 10.4.133.191 |
| 93 | 10.4.133.192/28 | 10.4.133.193 – 10.4.133.206 | 10.4.133.207 |
| 94 | 10.4.133.208/28 | 10.4.133.209 – 10.4.133.222 | 10.4.133.223 |
| 95 | 10.4.133.224/28 | 10.4.133.225 – 10.4.133.238 | 10.4.133.239 |
| 96 | 10.4.133.240/28 | 10.4.133.241 – 10.4.133.254 | 10.4.133.255 |
| 97 | 10.4.134.0/28 | 10.4.134.1 – 10.4.134.14 | 10.4.134.15 |
| 98 | 10.4.134.16/28 | 10.4.134.17 – 10.4.134.30 | 10.4.134.31 |
| 99 | 10.4.134.32/28 | 10.4.134.33 – 10.4.134.46 | 10.4.134.47 |
| 100 | 10.4.134.48/28 | 10.4.134.49 – 10.4.134.62 | 10.4.134.63 |
| 101 | 10.4.134.64/28 | 10.4.134.65 – 10.4.134.78 | 10.4.134.79 |
| 102 | 10.4.134.80/28 | 10.4.134.81 – 10.4.134.94 | 10.4.134.95 |
| 103 | 10.4.134.96/28 | 10.4.134.97 – 10.4.134.110 | 10.4.134.111 |
| 104 | 10.4.134.112/28 | 10.4.134.113 – 10.4.134.126 | 10.4.134.127 |
| 105 | 10.4.134.128/28 | 10.4.134.129 – 10.4.134.142 | 10.4.134.143 |
| 106 | 10.4.134.144/28 | 10.4.134.145 – 10.4.134.158 | 10.4.134.159 |
| 107 | 10.4.134.160/28 | 10.4.134.161 – 10.4.134.174 | 10.4.134.175 |
| 108 | 10.4.134.176/28 | 10.4.134.177 – 10.4.134.190 | 10.4.134.191 |
| 109 | 10.4.134.192/28 | 10.4.134.193 – 10.4.134.206 | 10.4.134.207 |
| 110 | 10.4.134.208/28 | 10.4.134.209 – 10.4.134.222 | 10.4.134.223 |
| 111 | 10.4.134.224/28 | 10.4.134.225 – 10.4.134.238 | 10.4.134.239 |
| 112 | 10.4.134.240/28 | 10.4.134.241 – 10.4.134.254 | 10.4.134.255 |
| 113 | 10.4.135.0/28 | 10.4.135.1 – 10.4.135.14 | 10.4.135.15 |
| 114 | 10.4.135.16/28 | 10.4.135.17 – 10.4.135.30 | 10.4.135.31 |
| 115 | 10.4.135.32/28 | 10.4.135.33 – 10.4.135.46 | 10.4.135.47 |
| 116 | 10.4.135.48/28 | 10.4.135.49 – 10.4.135.62 | 10.4.135.63 |
| 117 | 10.4.135.64/28 | 10.4.135.65 – 10.4.135.78 | 10.4.135.79 |
| 118 | 10.4.135.80/28 | 10.4.135.81 – 10.4.135.94 | 10.4.135.95 |
| 119 | 10.4.135.96/28 | 10.4.135.97 – 10.4.135.110 | 10.4.135.111 |
| 120 | 10.4.135.112/28 | 10.4.135.113 – 10.4.135.126 | 10.4.135.127 |
| 121 | 10.4.135.128/28 | 10.4.135.129 – 10.4.135.142 | 10.4.135.143 |
| 122 | 10.4.135.144/28 | 10.4.135.145 – 10.4.135.158 | 10.4.135.159 |
| 123 | 10.4.135.160/28 | 10.4.135.161 – 10.4.135.174 | 10.4.135.175 |
| 124 | 10.4.135.176/28 | 10.4.135.177 – 10.4.135.190 | 10.4.135.191 |
| 125 | 10.4.135.192/28 | 10.4.135.193 – 10.4.135.206 | 10.4.135.207 |
| 126 | 10.4.135.208/28 | 10.4.135.209 – 10.4.135.222 | 10.4.135.223 |
| 127 | 10.4.135.224/28 | 10.4.135.225 – 10.4.135.238 | 10.4.135.239 |
| 128 | 10.4.135.240/28 | 10.4.135.241 – 10.4.135.254 | 10.4.135.255 |
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.