The /5 subnet
A /5 subnet uses the mask 248.0.0.0 and holds 134,217,728 addresses, 134,217,726 of them usable.
A /5 is a very large IPv4 block. Its mask is 248.0.0.0 and it holds 134,217,728 addresses, which puts it at the scale of a regional allocation or an entire private supernet rather than a single LAN.
Networks this size are almost always carved into smaller subnets before use. You will see a /5 as an aggregate route or a private-address supernet such as 10.0.0.0/8, not as a single broadcast domain.
Below you can see the exact network, broadcast, and host range for any /5 you enter, calculated instantly in your browser.
Calculate a /5 network
Accepts CIDR (192.0.2.0/24), IP + mask (192.0.2.0 255.255.255.0), or a bare IP (defaults to /24).
00001010.00000000.00000000.0000000011111000.00000000.00000000.00000000Example: 10.0.0.0/5
Taking 10.0.0.0/5 as a worked example, the block breaks down like this:
| Network address | 8.0.0.0 |
|---|---|
| Usable range | 8.0.0.1 - 15.255.255.254 |
| Broadcast address | 15.255.255.255 |
| Total addresses | 134,217,728 |
| Usable hosts | 134,217,726 |
| Size | 8 class A blocks |
Frequently asked questions
What is the subnet mask for a /5?
A /5 uses the subnet mask 248.0.0.0. Its wildcard mask, used in access lists, is 7.255.255.255.
How many hosts are in a /5 subnet?
A /5 has 134,217,728 total addresses and 134,217,726 usable hosts (the total minus the network and broadcast addresses, except for /31 and /32).
What is a /5 used for?
Very large network. It is equivalent to 8 class A blocks.
How do I calculate a /5 network?
Set the host bits to zero for the network address and to one for the broadcast address. The calculator on this page does it for any /5 block you enter.