/2 vs /4 — Subnet Comparison
A /2 subnet is 4× larger than a /4. Every additional bit in the prefix halves the address space — the 2-bit difference between these two means /2 has 22 = 4 times as many addresses.
Key Differences
How 4 /4 Subnets Divide a /2
Example using 10.0.0.0/2 as the parent block.
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 0.0.0.0/4 | 0.0.0.0 | 0.0.0.1 | 15.255.255.254 | 15.255.255.255 | 268,435,454 |
| 2 | 16.0.0.0/4 | 16.0.0.0 | 16.0.0.1 | 31.255.255.254 | 31.255.255.255 | 268,435,454 |
| 3 | 32.0.0.0/4 | 32.0.0.0 | 32.0.0.1 | 47.255.255.254 | 47.255.255.255 | 268,435,454 |
| 4 | 48.0.0.0/4 | 48.0.0.0 | 48.0.0.1 | 63.255.255.254 | 63.255.255.255 | 268,435,454 |
FAQ
What is the difference between /2 and /4?
A /2 has 1,073,741,822 usable hosts
and a /4 has 268,435,454.
The subnet masks differ: /2 uses 192.0.0.0
while /4 uses 240.0.0.0.
Every additional bit in the prefix halves the number of addresses — so the 2-bit gap means
/2 is exactly 4× larger.
How many /4 subnets fit in a /2?
Exactly 4 /4 subnets fit perfectly inside one /2 with no wasted space. To split a /2 into /4s, 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.