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)172.16.8.0/21
network172.16.8.0/21
broadcast172.16.15.255
first host172.16.8.1
last host172.16.15.254
subnet mask255.255.248.0
wildcard0.0.7.255
addresses2,048
usable hosts2,046
classB
ipcalc 172.16.8.0/21
address10101100.00010000.00001000.00000000
subnet mask11111111.11111111.11111000.00000000
network10101100.00010000.00001000.00000000
broadcast10101100.00010000.00001111.11111111
green = network part, grey = host part
hex0xac100800
decimal2886731776
reverse dns0.8.16.172.in-addr.arpa
ipv4-mapped::ffff:ac10:800
/21 split into /28 · 128 subnets
close ×| # | network | host range | broadcast |
|---|---|---|---|
| 1 | 172.16.8.0/28 | 172.16.8.1 – 172.16.8.14 | 172.16.8.15 |
| 2 | 172.16.8.16/28 | 172.16.8.17 – 172.16.8.30 | 172.16.8.31 |
| 3 | 172.16.8.32/28 | 172.16.8.33 – 172.16.8.46 | 172.16.8.47 |
| 4 | 172.16.8.48/28 | 172.16.8.49 – 172.16.8.62 | 172.16.8.63 |
| 5 | 172.16.8.64/28 | 172.16.8.65 – 172.16.8.78 | 172.16.8.79 |
| 6 | 172.16.8.80/28 | 172.16.8.81 – 172.16.8.94 | 172.16.8.95 |
| 7 | 172.16.8.96/28 | 172.16.8.97 – 172.16.8.110 | 172.16.8.111 |
| 8 | 172.16.8.112/28 | 172.16.8.113 – 172.16.8.126 | 172.16.8.127 |
| 9 | 172.16.8.128/28 | 172.16.8.129 – 172.16.8.142 | 172.16.8.143 |
| 10 | 172.16.8.144/28 | 172.16.8.145 – 172.16.8.158 | 172.16.8.159 |
| 11 | 172.16.8.160/28 | 172.16.8.161 – 172.16.8.174 | 172.16.8.175 |
| 12 | 172.16.8.176/28 | 172.16.8.177 – 172.16.8.190 | 172.16.8.191 |
| 13 | 172.16.8.192/28 | 172.16.8.193 – 172.16.8.206 | 172.16.8.207 |
| 14 | 172.16.8.208/28 | 172.16.8.209 – 172.16.8.222 | 172.16.8.223 |
| 15 | 172.16.8.224/28 | 172.16.8.225 – 172.16.8.238 | 172.16.8.239 |
| 16 | 172.16.8.240/28 | 172.16.8.241 – 172.16.8.254 | 172.16.8.255 |
| 17 | 172.16.9.0/28 | 172.16.9.1 – 172.16.9.14 | 172.16.9.15 |
| 18 | 172.16.9.16/28 | 172.16.9.17 – 172.16.9.30 | 172.16.9.31 |
| 19 | 172.16.9.32/28 | 172.16.9.33 – 172.16.9.46 | 172.16.9.47 |
| 20 | 172.16.9.48/28 | 172.16.9.49 – 172.16.9.62 | 172.16.9.63 |
| 21 | 172.16.9.64/28 | 172.16.9.65 – 172.16.9.78 | 172.16.9.79 |
| 22 | 172.16.9.80/28 | 172.16.9.81 – 172.16.9.94 | 172.16.9.95 |
| 23 | 172.16.9.96/28 | 172.16.9.97 – 172.16.9.110 | 172.16.9.111 |
| 24 | 172.16.9.112/28 | 172.16.9.113 – 172.16.9.126 | 172.16.9.127 |
| 25 | 172.16.9.128/28 | 172.16.9.129 – 172.16.9.142 | 172.16.9.143 |
| 26 | 172.16.9.144/28 | 172.16.9.145 – 172.16.9.158 | 172.16.9.159 |
| 27 | 172.16.9.160/28 | 172.16.9.161 – 172.16.9.174 | 172.16.9.175 |
| 28 | 172.16.9.176/28 | 172.16.9.177 – 172.16.9.190 | 172.16.9.191 |
| 29 | 172.16.9.192/28 | 172.16.9.193 – 172.16.9.206 | 172.16.9.207 |
| 30 | 172.16.9.208/28 | 172.16.9.209 – 172.16.9.222 | 172.16.9.223 |
| 31 | 172.16.9.224/28 | 172.16.9.225 – 172.16.9.238 | 172.16.9.239 |
| 32 | 172.16.9.240/28 | 172.16.9.241 – 172.16.9.254 | 172.16.9.255 |
| 33 | 172.16.10.0/28 | 172.16.10.1 – 172.16.10.14 | 172.16.10.15 |
| 34 | 172.16.10.16/28 | 172.16.10.17 – 172.16.10.30 | 172.16.10.31 |
| 35 | 172.16.10.32/28 | 172.16.10.33 – 172.16.10.46 | 172.16.10.47 |
| 36 | 172.16.10.48/28 | 172.16.10.49 – 172.16.10.62 | 172.16.10.63 |
| 37 | 172.16.10.64/28 | 172.16.10.65 – 172.16.10.78 | 172.16.10.79 |
| 38 | 172.16.10.80/28 | 172.16.10.81 – 172.16.10.94 | 172.16.10.95 |
| 39 | 172.16.10.96/28 | 172.16.10.97 – 172.16.10.110 | 172.16.10.111 |
| 40 | 172.16.10.112/28 | 172.16.10.113 – 172.16.10.126 | 172.16.10.127 |
| 41 | 172.16.10.128/28 | 172.16.10.129 – 172.16.10.142 | 172.16.10.143 |
| 42 | 172.16.10.144/28 | 172.16.10.145 – 172.16.10.158 | 172.16.10.159 |
| 43 | 172.16.10.160/28 | 172.16.10.161 – 172.16.10.174 | 172.16.10.175 |
| 44 | 172.16.10.176/28 | 172.16.10.177 – 172.16.10.190 | 172.16.10.191 |
| 45 | 172.16.10.192/28 | 172.16.10.193 – 172.16.10.206 | 172.16.10.207 |
| 46 | 172.16.10.208/28 | 172.16.10.209 – 172.16.10.222 | 172.16.10.223 |
| 47 | 172.16.10.224/28 | 172.16.10.225 – 172.16.10.238 | 172.16.10.239 |
| 48 | 172.16.10.240/28 | 172.16.10.241 – 172.16.10.254 | 172.16.10.255 |
| 49 | 172.16.11.0/28 | 172.16.11.1 – 172.16.11.14 | 172.16.11.15 |
| 50 | 172.16.11.16/28 | 172.16.11.17 – 172.16.11.30 | 172.16.11.31 |
| 51 | 172.16.11.32/28 | 172.16.11.33 – 172.16.11.46 | 172.16.11.47 |
| 52 | 172.16.11.48/28 | 172.16.11.49 – 172.16.11.62 | 172.16.11.63 |
| 53 | 172.16.11.64/28 | 172.16.11.65 – 172.16.11.78 | 172.16.11.79 |
| 54 | 172.16.11.80/28 | 172.16.11.81 – 172.16.11.94 | 172.16.11.95 |
| 55 | 172.16.11.96/28 | 172.16.11.97 – 172.16.11.110 | 172.16.11.111 |
| 56 | 172.16.11.112/28 | 172.16.11.113 – 172.16.11.126 | 172.16.11.127 |
| 57 | 172.16.11.128/28 | 172.16.11.129 – 172.16.11.142 | 172.16.11.143 |
| 58 | 172.16.11.144/28 | 172.16.11.145 – 172.16.11.158 | 172.16.11.159 |
| 59 | 172.16.11.160/28 | 172.16.11.161 – 172.16.11.174 | 172.16.11.175 |
| 60 | 172.16.11.176/28 | 172.16.11.177 – 172.16.11.190 | 172.16.11.191 |
| 61 | 172.16.11.192/28 | 172.16.11.193 – 172.16.11.206 | 172.16.11.207 |
| 62 | 172.16.11.208/28 | 172.16.11.209 – 172.16.11.222 | 172.16.11.223 |
| 63 | 172.16.11.224/28 | 172.16.11.225 – 172.16.11.238 | 172.16.11.239 |
| 64 | 172.16.11.240/28 | 172.16.11.241 – 172.16.11.254 | 172.16.11.255 |
| 65 | 172.16.12.0/28 | 172.16.12.1 – 172.16.12.14 | 172.16.12.15 |
| 66 | 172.16.12.16/28 | 172.16.12.17 – 172.16.12.30 | 172.16.12.31 |
| 67 | 172.16.12.32/28 | 172.16.12.33 – 172.16.12.46 | 172.16.12.47 |
| 68 | 172.16.12.48/28 | 172.16.12.49 – 172.16.12.62 | 172.16.12.63 |
| 69 | 172.16.12.64/28 | 172.16.12.65 – 172.16.12.78 | 172.16.12.79 |
| 70 | 172.16.12.80/28 | 172.16.12.81 – 172.16.12.94 | 172.16.12.95 |
| 71 | 172.16.12.96/28 | 172.16.12.97 – 172.16.12.110 | 172.16.12.111 |
| 72 | 172.16.12.112/28 | 172.16.12.113 – 172.16.12.126 | 172.16.12.127 |
| 73 | 172.16.12.128/28 | 172.16.12.129 – 172.16.12.142 | 172.16.12.143 |
| 74 | 172.16.12.144/28 | 172.16.12.145 – 172.16.12.158 | 172.16.12.159 |
| 75 | 172.16.12.160/28 | 172.16.12.161 – 172.16.12.174 | 172.16.12.175 |
| 76 | 172.16.12.176/28 | 172.16.12.177 – 172.16.12.190 | 172.16.12.191 |
| 77 | 172.16.12.192/28 | 172.16.12.193 – 172.16.12.206 | 172.16.12.207 |
| 78 | 172.16.12.208/28 | 172.16.12.209 – 172.16.12.222 | 172.16.12.223 |
| 79 | 172.16.12.224/28 | 172.16.12.225 – 172.16.12.238 | 172.16.12.239 |
| 80 | 172.16.12.240/28 | 172.16.12.241 – 172.16.12.254 | 172.16.12.255 |
| 81 | 172.16.13.0/28 | 172.16.13.1 – 172.16.13.14 | 172.16.13.15 |
| 82 | 172.16.13.16/28 | 172.16.13.17 – 172.16.13.30 | 172.16.13.31 |
| 83 | 172.16.13.32/28 | 172.16.13.33 – 172.16.13.46 | 172.16.13.47 |
| 84 | 172.16.13.48/28 | 172.16.13.49 – 172.16.13.62 | 172.16.13.63 |
| 85 | 172.16.13.64/28 | 172.16.13.65 – 172.16.13.78 | 172.16.13.79 |
| 86 | 172.16.13.80/28 | 172.16.13.81 – 172.16.13.94 | 172.16.13.95 |
| 87 | 172.16.13.96/28 | 172.16.13.97 – 172.16.13.110 | 172.16.13.111 |
| 88 | 172.16.13.112/28 | 172.16.13.113 – 172.16.13.126 | 172.16.13.127 |
| 89 | 172.16.13.128/28 | 172.16.13.129 – 172.16.13.142 | 172.16.13.143 |
| 90 | 172.16.13.144/28 | 172.16.13.145 – 172.16.13.158 | 172.16.13.159 |
| 91 | 172.16.13.160/28 | 172.16.13.161 – 172.16.13.174 | 172.16.13.175 |
| 92 | 172.16.13.176/28 | 172.16.13.177 – 172.16.13.190 | 172.16.13.191 |
| 93 | 172.16.13.192/28 | 172.16.13.193 – 172.16.13.206 | 172.16.13.207 |
| 94 | 172.16.13.208/28 | 172.16.13.209 – 172.16.13.222 | 172.16.13.223 |
| 95 | 172.16.13.224/28 | 172.16.13.225 – 172.16.13.238 | 172.16.13.239 |
| 96 | 172.16.13.240/28 | 172.16.13.241 – 172.16.13.254 | 172.16.13.255 |
| 97 | 172.16.14.0/28 | 172.16.14.1 – 172.16.14.14 | 172.16.14.15 |
| 98 | 172.16.14.16/28 | 172.16.14.17 – 172.16.14.30 | 172.16.14.31 |
| 99 | 172.16.14.32/28 | 172.16.14.33 – 172.16.14.46 | 172.16.14.47 |
| 100 | 172.16.14.48/28 | 172.16.14.49 – 172.16.14.62 | 172.16.14.63 |
| 101 | 172.16.14.64/28 | 172.16.14.65 – 172.16.14.78 | 172.16.14.79 |
| 102 | 172.16.14.80/28 | 172.16.14.81 – 172.16.14.94 | 172.16.14.95 |
| 103 | 172.16.14.96/28 | 172.16.14.97 – 172.16.14.110 | 172.16.14.111 |
| 104 | 172.16.14.112/28 | 172.16.14.113 – 172.16.14.126 | 172.16.14.127 |
| 105 | 172.16.14.128/28 | 172.16.14.129 – 172.16.14.142 | 172.16.14.143 |
| 106 | 172.16.14.144/28 | 172.16.14.145 – 172.16.14.158 | 172.16.14.159 |
| 107 | 172.16.14.160/28 | 172.16.14.161 – 172.16.14.174 | 172.16.14.175 |
| 108 | 172.16.14.176/28 | 172.16.14.177 – 172.16.14.190 | 172.16.14.191 |
| 109 | 172.16.14.192/28 | 172.16.14.193 – 172.16.14.206 | 172.16.14.207 |
| 110 | 172.16.14.208/28 | 172.16.14.209 – 172.16.14.222 | 172.16.14.223 |
| 111 | 172.16.14.224/28 | 172.16.14.225 – 172.16.14.238 | 172.16.14.239 |
| 112 | 172.16.14.240/28 | 172.16.14.241 – 172.16.14.254 | 172.16.14.255 |
| 113 | 172.16.15.0/28 | 172.16.15.1 – 172.16.15.14 | 172.16.15.15 |
| 114 | 172.16.15.16/28 | 172.16.15.17 – 172.16.15.30 | 172.16.15.31 |
| 115 | 172.16.15.32/28 | 172.16.15.33 – 172.16.15.46 | 172.16.15.47 |
| 116 | 172.16.15.48/28 | 172.16.15.49 – 172.16.15.62 | 172.16.15.63 |
| 117 | 172.16.15.64/28 | 172.16.15.65 – 172.16.15.78 | 172.16.15.79 |
| 118 | 172.16.15.80/28 | 172.16.15.81 – 172.16.15.94 | 172.16.15.95 |
| 119 | 172.16.15.96/28 | 172.16.15.97 – 172.16.15.110 | 172.16.15.111 |
| 120 | 172.16.15.112/28 | 172.16.15.113 – 172.16.15.126 | 172.16.15.127 |
| 121 | 172.16.15.128/28 | 172.16.15.129 – 172.16.15.142 | 172.16.15.143 |
| 122 | 172.16.15.144/28 | 172.16.15.145 – 172.16.15.158 | 172.16.15.159 |
| 123 | 172.16.15.160/28 | 172.16.15.161 – 172.16.15.174 | 172.16.15.175 |
| 124 | 172.16.15.176/28 | 172.16.15.177 – 172.16.15.190 | 172.16.15.191 |
| 125 | 172.16.15.192/28 | 172.16.15.193 – 172.16.15.206 | 172.16.15.207 |
| 126 | 172.16.15.208/28 | 172.16.15.209 – 172.16.15.222 | 172.16.15.223 |
| 127 | 172.16.15.224/28 | 172.16.15.225 – 172.16.15.238 | 172.16.15.239 |
| 128 | 172.16.15.240/28 | 172.16.15.241 – 172.16.15.254 | 172.16.15.255 |
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.