/4 vs /5 — Subnet Comparison
A /4 subnet is 2× larger than a /5. Every additional bit in the prefix halves the address space — the 1-bit difference between these two means /4 has 21 = 2 times as many addresses.
Key Differences
How 2 /5 Subnets Divide a /4
Example using 10.0.0.0/4 as the parent block.
FAQ
What is the difference between /4 and /5?
A /4 has 268,435,454 usable hosts
and a /5 has 134,217,726.
The subnet masks differ: /4 uses 240.0.0.0
while /5 uses 248.0.0.0.
Every additional bit in the prefix halves the number of addresses — so the 1-bit gap means
/4 is exactly 2× larger.
How many /5 subnets fit in a /4?
Exactly 2 /5 subnets fit perfectly inside one /4 with no wasted space. To split a /4 into /5s, just increment the last 1 bit 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.