/13 vs /15 — Subnet Comparison
A /13 subnet is 4× larger than a /15. Every additional bit in the prefix halves the address space — the 2-bit difference between these two means /13 has 22 = 4 times as many addresses.
Key Differences
How 4 /15 Subnets Divide a /13
Example using 10.0.0.0/13 as the parent block.
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 10.0.0.0/15 | 10.0.0.0 | 10.0.0.1 | 10.1.255.254 | 10.1.255.255 | 131,070 |
| 2 | 10.2.0.0/15 | 10.2.0.0 | 10.2.0.1 | 10.3.255.254 | 10.3.255.255 | 131,070 |
| 3 | 10.4.0.0/15 | 10.4.0.0 | 10.4.0.1 | 10.5.255.254 | 10.5.255.255 | 131,070 |
| 4 | 10.6.0.0/15 | 10.6.0.0 | 10.6.0.1 | 10.7.255.254 | 10.7.255.255 | 131,070 |
FAQ
What is the difference between /13 and /15?
A /13 has 524,286 usable hosts
and a /15 has 131,070.
The subnet masks differ: /13 uses 255.248.0.0
while /15 uses 255.254.0.0.
Every additional bit in the prefix halves the number of addresses — so the 2-bit gap means
/13 is exactly 4× larger.
How many /15 subnets fit in a /13?
Exactly 4 /15 subnets fit perfectly inside one /13 with no wasted space. To split a /13 into /15s, just increment the last 2 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.