/2 vs /3 — Subnet Comparison
A /2 subnet is 2× larger than a /3. Every additional bit in the prefix halves the address space — the 1-bit difference between these two means /2 has 21 = 2 times as many addresses.
Key Differences
How 2 /3 Subnets Divide a /2
Example using 10.0.0.0/2 as the parent block.
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 0.0.0.0/3 | 0.0.0.0 | 0.0.0.1 | 31.255.255.254 | 31.255.255.255 | 536,870,910 |
| 2 | 32.0.0.0/3 | 32.0.0.0 | 32.0.0.1 | 63.255.255.254 | 63.255.255.255 | 536,870,910 |
FAQ
What is the difference between /2 and /3?
A /2 has 1,073,741,822 usable hosts
and a /3 has 536,870,910.
The subnet masks differ: /2 uses 192.0.0.0
while /3 uses 224.0.0.0.
Every additional bit in the prefix halves the number of addresses — so the 1-bit gap means
/2 is exactly 2× larger.
How many /3 subnets fit in a /2?
Exactly 2 /3 subnets fit perfectly inside one /2 with no wasted space. To split a /2 into /3s, 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.