/13 vs /17 — Subnet Comparison
A /13 subnet is 16× larger than a /17. Every additional bit in the prefix halves the address space — the 4-bit difference between these two means /13 has 24 = 16 times as many addresses.
32K IPs — half a /16
Typical Uses
- →Half of a /16 VPC split public/private
- →Large campus segment
Key Differences
How 16 /17 Subnets Divide a /13
Example using 10.0.0.0/13 as the parent block.
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 10.0.0.0/17 | 10.0.0.0 | 10.0.0.1 | 10.0.127.254 | 10.0.127.255 | 32,766 |
| 2 | 10.0.128.0/17 | 10.0.128.0 | 10.0.128.1 | 10.0.255.254 | 10.0.255.255 | 32,766 |
| 3 | 10.1.0.0/17 | 10.1.0.0 | 10.1.0.1 | 10.1.127.254 | 10.1.127.255 | 32,766 |
| 4 | 10.1.128.0/17 | 10.1.128.0 | 10.1.128.1 | 10.1.255.254 | 10.1.255.255 | 32,766 |
| 5 | 10.2.0.0/17 | 10.2.0.0 | 10.2.0.1 | 10.2.127.254 | 10.2.127.255 | 32,766 |
| 6 | 10.2.128.0/17 | 10.2.128.0 | 10.2.128.1 | 10.2.255.254 | 10.2.255.255 | 32,766 |
| 7 | 10.3.0.0/17 | 10.3.0.0 | 10.3.0.1 | 10.3.127.254 | 10.3.127.255 | 32,766 |
| 8 | 10.3.128.0/17 | 10.3.128.0 | 10.3.128.1 | 10.3.255.254 | 10.3.255.255 | 32,766 |
| 9 | 10.4.0.0/17 | 10.4.0.0 | 10.4.0.1 | 10.4.127.254 | 10.4.127.255 | 32,766 |
| 10 | 10.4.128.0/17 | 10.4.128.0 | 10.4.128.1 | 10.4.255.254 | 10.4.255.255 | 32,766 |
| 11 | 10.5.0.0/17 | 10.5.0.0 | 10.5.0.1 | 10.5.127.254 | 10.5.127.255 | 32,766 |
| 12 | 10.5.128.0/17 | 10.5.128.0 | 10.5.128.1 | 10.5.255.254 | 10.5.255.255 | 32,766 |
| 13 | 10.6.0.0/17 | 10.6.0.0 | 10.6.0.1 | 10.6.127.254 | 10.6.127.255 | 32,766 |
| 14 | 10.6.128.0/17 | 10.6.128.0 | 10.6.128.1 | 10.6.255.254 | 10.6.255.255 | 32,766 |
| 15 | 10.7.0.0/17 | 10.7.0.0 | 10.7.0.1 | 10.7.127.254 | 10.7.127.255 | 32,766 |
| 16 | 10.7.128.0/17 | 10.7.128.0 | 10.7.128.1 | 10.7.255.254 | 10.7.255.255 | 32,766 |
FAQ
What is the difference between /13 and /17?
A /13 has 524,286 usable hosts
and a /17 has 32,766.
The subnet masks differ: /13 uses 255.248.0.0
while /17 uses 255.255.128.0.
Every additional bit in the prefix halves the number of addresses — so the 4-bit gap means
/13 is exactly 16× larger.
How many /17 subnets fit in a /13?
Exactly 16 /17 subnets fit perfectly inside one /13 with no wasted space. To split a /13 into /17s, 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.