The /13 subnet, explained
Everything about a /13 CIDR block — mask, address count, usable hosts and where a /13 fits in real network plans.
| Prefix length | /13 — 13 network bits, 19 host bits |
| Subnet mask | 255.248.0.0 |
| Wildcard (ACL) mask | 0.7.255.255 |
| Binary mask | 11111111.11111000.00000000.00000000 |
| Total addresses | 2^19 = 524,288 |
| Usable hosts | 524,286 (total − network − broadcast) |
| Contains | 2,048 × /24 subnets |
| Example block | 10.0.0.0/13 |
Notes
A /13 prefix means the first 13 bits of the 32-bit IPv4 address identify the network and the remaining 19 bits identify hosts — giving 2^19 = 524,288 addresses. The first address (network) and the last (broadcast) are not assignable in a standard subnet.
Cloud sizing: a /13 is larger than the maximum AWS VPC (/16). Blocks this size are carved into multiple VPCs or used in on-prem/enterprise addressing plans.
Adjacent sizes: /8 · /9 · /10 · /11 · /12 · /14 · /15 · /16 · /17 · /18 · /19 · /20 · /21 · /22 · /23 · /24 · /25 · /26 · /27 · /28 · /29 · /30 · /31 · /32
Frequently asked questions
How many IP addresses are in a /13?
524,288 total addresses, of which 524,286 are usable hosts (network and broadcast addresses are reserved).
What is the subnet mask for /13?
255.248.0.0 (wildcard mask 0.7.255.255).
What does /13 mean in an IP address?
The /13 suffix is CIDR notation: the first 13 bits are the network part, the last 19 bits are the host part.