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 |
A /8 subnet contains 16,777,216 total IP addresses and 16,777,214 usable host addresses. The subnet mask is 255.0.0.0, leaving 24 bits for host addressing (2^24 = 16,777,216).
10.0.0.0/8 is an RFC 1918 private address range — the largest private IP block available. It contains over 16 million addresses, making it the standard choice for large enterprise networks, cloud VPC addressing, and any environment that needs to avoid running out of private IPs.
In classful networking (pre-CIDR), a Class A network was any network where the first bit was 0, giving it a /8 mask by default. Today, CIDR (Classless Inter-Domain Routing) replaces classful networking, so /8 simply means 8 bits for the network prefix — the class designation is no longer used in modern routing.