/3 Subnet: Mask 224.0.0.0, 536,870,910 Usable Hosts
A /3 subnet has a subnet mask of 224.0.0.0 and contains 536,870,912 total IP addresses, of which 536,870,910 are usable host addresses (the network and broadcast addresses are reserved). A /3 contains 2,097,152 /24 networks.
| CIDR notation | /3 |
|---|---|
| Subnet mask | 224.0.0.0 |
| Wildcard mask | 31.255.255.255 |
| Mask in binary | 11100000.00000000.00000000.00000000 |
| Total addresses | 536,870,912 (2^29) |
| Usable hosts | 536,870,910 |
| Host bits | 29 |
Usable hosts in a /3 by platform
Cloud providers reserve more than the usual two addresses per subnet, so the same /3 gives you fewer usable IPs in the cloud than on a standard LAN.
| Platform | Reserved IPs | Usable hosts |
|---|---|---|
| Standard (network + broadcast) | 2 | 536,870,910 |
| AWS VPC | 5 | 536,870,907 |
| Microsoft Azure VNet | 5 | 536,870,907 |
| Google Cloud VPC | 4 | 536,870,908 |
| Oracle Cloud VCN | 3 | 536,870,909 |
Good to know
A /3 subnet has a 224.0.0.0 mask and 536,870,912 total addresses (536,870,910 usable). Each step from /3 to /4 halves the block; each step back to /2 doubles it.
How a /3 is calculated
- The /3 means the first 3 bits are the network portion, leaving 29 host bits.
- Total addresses = 2^(32 - 3) = 2^29 = 536,870,912.
- Usable hosts (standard) = 536,870,912 - 2 (network + broadcast) = 536,870,910.
- Subnet mask = 224.0.0.0; wildcard mask = 31.255.255.255.
Want to split a /3 into smaller subnets, see every address range, or plan a VLSM layout? Open the free subnet calculator →