/8 Subnet Mask: 255.0.0.0 (16,777,214 Usable Hosts)

A /8 subnet mask is 255.0.0.0, with 16,777,216 addresses and 16,777,214 usable hosts.

CIDR prefix	/8
Subnet mask	255.0.0.0
Subnet mask (binary)	`11111111.00000000.00000000.00000000`
Wildcard mask	0.255.255.255
Network bits / host bits	8 / 24
Total addresses	16,777,216
Usable hosts	16,777,214

The mask ends exactly on an octet boundary, so every address in a /8 block shares its first 1 octet. The size of the classic Class A block, and of the 10.0.0.0/8 private range. Far too large for a single broadcast domain, so it is carved into smaller subnets.

Try it with an address

Example /8 subnets in 10.0.0.0/8

Network	First usable host	Last usable host	Broadcast
10.0.0.0/8	10.0.0.1	10.255.255.254	10.255.255.255

Frequently asked questions

What is the subnet mask for /8?

A /8 subnet mask is 255.0.0.0. In binary that is 11111111.00000000.00000000.00000000: 8 network bits followed by 24 host bits. The wildcard mask is 0.255.255.255.

How many usable hosts are in a /8?

A /8 holds 16,777,216 addresses in total. Subtracting the network and broadcast addresses leaves 16,777,214 usable hosts.

Other prefix lengths

Calculate this over HTTP: curl https://networkcalc.com/api/ip/192.168.1.0/8. See the Subnet Calculator API.