Last reviewed: May 2026
A /8 subnet uses 8 bits for the network portion of an IPv4 address, leaving 24 bits for host addressing. This produces 16,777,216 total IP addresses — enough to number every device in a large ISP, cloud region, or global enterprise. Historically called a "Class A" network, the /8 is most commonly encountered as 10.0.0.0/8, the largest RFC 1918 private address range.
Calculate any /8 subnet instantly →| Property | Value |
|---|---|
| Prefix length | /8 |
| Subnet mask | 255.0.0.0 |
| Wildcard mask | 0.255.255.255 |
| Total addresses | 16,777,216 |
| Usable host addresses | 16,777,214 |
| Network address | x.0.0.0 |
| Broadcast address | x.255.255.255 |
| Binary mask | 11111111.00000000.00000000.00000000 |
10.0.0.0/8 is the largest private IP range defined in RFC 1918. With over 16 million addresses, it is the standard starting block for large enterprises and cloud environments. A single 10.x.x.x space can contain 65,536 separate /24 subnets or 256 /16 VPCs — far more than any organisation needs.
| Block | Type | Description |
|---|---|---|
| 10.0.0.0/8 | RFC 1918 private | Largest private range; standard for enterprises and cloud VPCs |
| 127.0.0.0/8 | Loopback | Reserved for localhost (127.0.0.1 is the standard loopback address) |
| 100.64.0.0/10 | Shared address space (RFC 6598) | Used by ISPs for carrier-grade NAT — not a /8, but worth noting |
| Subnet Size | Number in a /8 | Usable Hosts Each |
|---|---|---|
| /16 | 256 | 65,534 |
| /20 | 4,096 | 4,094 |
| /24 | 65,536 | 254 |
| /26 | 262,144 | 62 |
| /28 | 1,048,576 | 14 |
In classful networking (used before 1993), a "Class A" network was any IPv4 address starting with a 0-bit, giving it an automatic /8 mask. With CIDR (RFC 4632), prefix lengths are explicit — /8 simply means 8 network bits, with no implicit class. Modern routers use CIDR exclusively; the Class A/B/C distinction is a legacy concept still taught in CCNA but not used in practice.
| CIDR | Subnet Mask | Total IPs | Typical Use |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 | RFC 1918 10.x.x.x, ISP allocations |
| /12 | 255.240.0.0 | 1,048,576 | 172.16.0.0/12 RFC 1918 block |
| /16 | 255.255.0.0 | 65,536 | VPC root CIDR, campus network |
| /24 | 255.255.255.0 | 256 | Standard workload subnet |