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)172.16.0.0/21
network172.16.0.0/21
broadcast172.16.7.255
first host172.16.0.1
last host172.16.7.254
subnet mask255.255.248.0
wildcard0.0.7.255
addresses2,048
usable hosts2,046
classB
ipcalc 172.16.0.0/21
address10101100.00010000.00000000.00000000
subnet mask11111111.11111111.11111000.00000000
network10101100.00010000.00000000.00000000
broadcast10101100.00010000.00000111.11111111
green = network part, grey = host part
hex0xac100000
decimal2886729728
reverse dns0.0.16.172.in-addr.arpa
ipv4-mapped::ffff:ac10:0
/21 split into /26 · 32 subnets
close ×| # | network | host range | broadcast |
|---|---|---|---|
| 1 | 172.16.0.0/26 | 172.16.0.1 – 172.16.0.62 | 172.16.0.63 |
| 2 | 172.16.0.64/26 | 172.16.0.65 – 172.16.0.126 | 172.16.0.127 |
| 3 | 172.16.0.128/26 | 172.16.0.129 – 172.16.0.190 | 172.16.0.191 |
| 4 | 172.16.0.192/26 | 172.16.0.193 – 172.16.0.254 | 172.16.0.255 |
| 5 | 172.16.1.0/26 | 172.16.1.1 – 172.16.1.62 | 172.16.1.63 |
| 6 | 172.16.1.64/26 | 172.16.1.65 – 172.16.1.126 | 172.16.1.127 |
| 7 | 172.16.1.128/26 | 172.16.1.129 – 172.16.1.190 | 172.16.1.191 |
| 8 | 172.16.1.192/26 | 172.16.1.193 – 172.16.1.254 | 172.16.1.255 |
| 9 | 172.16.2.0/26 | 172.16.2.1 – 172.16.2.62 | 172.16.2.63 |
| 10 | 172.16.2.64/26 | 172.16.2.65 – 172.16.2.126 | 172.16.2.127 |
| 11 | 172.16.2.128/26 | 172.16.2.129 – 172.16.2.190 | 172.16.2.191 |
| 12 | 172.16.2.192/26 | 172.16.2.193 – 172.16.2.254 | 172.16.2.255 |
| 13 | 172.16.3.0/26 | 172.16.3.1 – 172.16.3.62 | 172.16.3.63 |
| 14 | 172.16.3.64/26 | 172.16.3.65 – 172.16.3.126 | 172.16.3.127 |
| 15 | 172.16.3.128/26 | 172.16.3.129 – 172.16.3.190 | 172.16.3.191 |
| 16 | 172.16.3.192/26 | 172.16.3.193 – 172.16.3.254 | 172.16.3.255 |
| 17 | 172.16.4.0/26 | 172.16.4.1 – 172.16.4.62 | 172.16.4.63 |
| 18 | 172.16.4.64/26 | 172.16.4.65 – 172.16.4.126 | 172.16.4.127 |
| 19 | 172.16.4.128/26 | 172.16.4.129 – 172.16.4.190 | 172.16.4.191 |
| 20 | 172.16.4.192/26 | 172.16.4.193 – 172.16.4.254 | 172.16.4.255 |
| 21 | 172.16.5.0/26 | 172.16.5.1 – 172.16.5.62 | 172.16.5.63 |
| 22 | 172.16.5.64/26 | 172.16.5.65 – 172.16.5.126 | 172.16.5.127 |
| 23 | 172.16.5.128/26 | 172.16.5.129 – 172.16.5.190 | 172.16.5.191 |
| 24 | 172.16.5.192/26 | 172.16.5.193 – 172.16.5.254 | 172.16.5.255 |
| 25 | 172.16.6.0/26 | 172.16.6.1 – 172.16.6.62 | 172.16.6.63 |
| 26 | 172.16.6.64/26 | 172.16.6.65 – 172.16.6.126 | 172.16.6.127 |
| 27 | 172.16.6.128/26 | 172.16.6.129 – 172.16.6.190 | 172.16.6.191 |
| 28 | 172.16.6.192/26 | 172.16.6.193 – 172.16.6.254 | 172.16.6.255 |
| 29 | 172.16.7.0/26 | 172.16.7.1 – 172.16.7.62 | 172.16.7.63 |
| 30 | 172.16.7.64/26 | 172.16.7.65 – 172.16.7.126 | 172.16.7.127 |
| 31 | 172.16.7.128/26 | 172.16.7.129 – 172.16.7.190 | 172.16.7.191 |
| 32 | 172.16.7.192/26 | 172.16.7.193 – 172.16.7.254 | 172.16.7.255 |
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.