/1 vs /2 — Subnet Comparison
A /1 subnet is 2× larger than a /2. Every additional bit in the prefix halves the address space — the 1-bit difference between these two means /1 has 21 = 2 times as many addresses.
Key Differences
How 2 /2 Subnets Divide a /1
Example using 10.0.0.0/1 as the parent block.
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 0.0.0.0/2 | 0.0.0.0 | 0.0.0.1 | 63.255.255.254 | 63.255.255.255 | 1,073,741,822 |
| 2 | 64.0.0.0/2 | 64.0.0.0 | 64.0.0.1 | 127.255.255.254 | 127.255.255.255 | 1,073,741,822 |
FAQ
What is the difference between /1 and /2?
A /1 has 2,147,483,646 usable hosts
and a /2 has 1,073,741,822.
The subnet masks differ: /1 uses 128.0.0.0
while /2 uses 192.0.0.0.
Every additional bit in the prefix halves the number of addresses — so the 1-bit gap means
/1 is exactly 2× larger.
How many /2 subnets fit in a /1?
Exactly 2 /2 subnets fit perfectly inside one /1 with no wasted space. To split a /1 into /2s, 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.