IPRangeExplorer

/9 vs /13 — Subnet Comparison

A /9 subnet is 16× larger than a /13. Every additional bit in the prefix halves the address space — the 4-bit difference between these two means /9 has 24 = 16 times as many addresses.

/9

8.3 million IPs — half a /8

Full reference →
Total IPs 8,388,608
Usable Hosts 8,388,606
Subnet Mask 255.128.0.0
Wildcard Mask 0.127.255.255

Typical Uses

  • →Large regional ISP allocation
  • →Half of a Class A block
  • →Aggregated routing prefix
/13
Full reference →
Total IPs 524,288
Usable Hosts 524,286
Subnet Mask 255.248.0.0
Wildcard Mask 0.7.255.255

Key Differences

16×
more IPs in /9 than /13
16
/13 subnets fit inside one /9
4
bits of difference in prefix length

How 16 /13 Subnets Divide a /9

Example using 10.0.0.0/9 as the parent block.

# CIDR Network First Usable Last Usable Broadcast Hosts
1 10.0.0.0/13 10.0.0.0 10.0.0.1 10.7.255.254 10.7.255.255 524,286
2 10.8.0.0/13 10.8.0.0 10.8.0.1 10.15.255.254 10.15.255.255 524,286
3 10.16.0.0/13 10.16.0.0 10.16.0.1 10.23.255.254 10.23.255.255 524,286
4 10.24.0.0/13 10.24.0.0 10.24.0.1 10.31.255.254 10.31.255.255 524,286
5 10.32.0.0/13 10.32.0.0 10.32.0.1 10.39.255.254 10.39.255.255 524,286
6 10.40.0.0/13 10.40.0.0 10.40.0.1 10.47.255.254 10.47.255.255 524,286
7 10.48.0.0/13 10.48.0.0 10.48.0.1 10.55.255.254 10.55.255.255 524,286
8 10.56.0.0/13 10.56.0.0 10.56.0.1 10.63.255.254 10.63.255.255 524,286
9 10.64.0.0/13 10.64.0.0 10.64.0.1 10.71.255.254 10.71.255.255 524,286
10 10.72.0.0/13 10.72.0.0 10.72.0.1 10.79.255.254 10.79.255.255 524,286
11 10.80.0.0/13 10.80.0.0 10.80.0.1 10.87.255.254 10.87.255.255 524,286
12 10.88.0.0/13 10.88.0.0 10.88.0.1 10.95.255.254 10.95.255.255 524,286
13 10.96.0.0/13 10.96.0.0 10.96.0.1 10.103.255.254 10.103.255.255 524,286
14 10.104.0.0/13 10.104.0.0 10.104.0.1 10.111.255.254 10.111.255.255 524,286
15 10.112.0.0/13 10.112.0.0 10.112.0.1 10.119.255.254 10.119.255.255 524,286
16 10.120.0.0/13 10.120.0.0 10.120.0.1 10.127.255.254 10.127.255.255 524,286

FAQ

What is the difference between /9 and /13?

A /9 has 8,388,606 usable hosts and a /13 has 524,286. The subnet masks differ: /9 uses 255.128.0.0 while /13 uses 255.248.0.0. Every additional bit in the prefix halves the number of addresses — so the 4-bit gap means /9 is exactly 16× larger.

How many /13 subnets fit in a /9?

Exactly 16 /13 subnets fit perfectly inside one /9 with no wasted space. To split a /9 into /13s, just increment the last 4 bits of the network address for each new subnet.

Which should I choose?

Choose based on how many hosts you need. Use the hosts → prefix calculator on the homepage to find the right size for your requirements.