/12 Subnet
1 million IPs — the 172.16/12 range
A /12 block holds just over 1 million addresses. The 172.16.0.0/12 RFC 1918 range is a /12, covering 172.16.0.0 through 172.31.255.255.
Common Use Cases
- → RFC 1918 Class B private range (172.16.0.0/12)
- → Large enterprise segments
Example /12 Networks
| CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|
| 10.0.0.0/12 | 10.0.0.0 | 10.0.0.1 | 10.15.255.254 | 10.15.255.255 | 1,048,574 |
| 172.16.0.0/12 | 172.16.0.0 | 172.16.0.1 | 172.31.255.254 | 172.31.255.255 | 1,048,574 |
| 172.16.0.0/12 | 172.16.0.0 | 172.16.0.1 | 172.31.255.254 | 172.31.255.255 | 1,048,574 |
| 192.160.0.0/12 | 192.160.0.0 | 192.160.0.1 | 192.175.255.254 | 192.175.255.255 | 1,048,574 |
| 192.160.0.0/12 | 192.160.0.0 | 192.160.0.1 | 192.175.255.254 | 192.175.255.255 | 1,048,574 |
| 10.0.0.0/12 | 10.0.0.0 | 10.0.0.1 | 10.15.255.254 | 10.15.255.255 | 1,048,574 |
How /12 Compares
| Prefix | Total IPs | Usable Hosts | Subnet Mask | Typical Use |
|---|---|---|---|---|
| /9 | 8,388,608 | 8,388,606 | 255.128.0.0 | Large regional allocations |
| /10 | 4,194,304 | 4,194,302 | 255.192.0.0 | Enterprise regional segment |
| /11 | 2,097,152 | 2,097,150 | 255.224.0.0 | — |
| /12 ◀ | 1,048,576 | 1,048,574 | 255.240.0.0 | RFC 1918 Class B range |
| /13 | 524,288 | 524,286 | 255.248.0.0 | — |
| /14 | 262,144 | 262,142 | 255.252.0.0 | — |
| /15 | 131,072 | 131,070 | 255.254.0.0 | — |
Frequently Asked Questions
How many IPs are in a /12?
A /12 subnet contains 1,048,576 total IP addresses and 1,048,574 usable host addresses. The network address (first IP) and broadcast address (last IP) are reserved and cannot be assigned to hosts.
What is the subnet mask for /12?
The subnet mask for a /12 is 255.240.0.0.
In CIDR notation, the prefix length /12 means
the first 12 bits of the address are the network portion.
The wildcard (inverse) mask is 0.15.255.255.
How many /12 subnets fit in a /11?
Exactly 2 — a /11 can be split into two /12 subnets of equal size.