/4 vs /8 — Subnet Comparison
A /4 subnet is 16× larger than a /8. Every additional bit in the prefix halves the address space — the 4-bit difference between these two means /4 has 24 = 16 times as many addresses.
16 million IPs — Class A network
Typical Uses
- →Entire Class A private range (10.0.0.0/8)
- →Large ISP or carrier allocations
- →Enterprise-wide addressing plan
Key Differences
How 16 /8 Subnets Divide a /4
Example using 10.0.0.0/4 as the parent block.
| # | CIDR | Network | First Usable | Last Usable | Broadcast | Hosts |
|---|---|---|---|---|---|---|
| 1 | 0.0.0.0/8 | 0.0.0.0 | 0.0.0.1 | 0.255.255.254 | 0.255.255.255 | 16,777,214 |
| 2 | 1.0.0.0/8 | 1.0.0.0 | 1.0.0.1 | 1.255.255.254 | 1.255.255.255 | 16,777,214 |
| 3 | 2.0.0.0/8 | 2.0.0.0 | 2.0.0.1 | 2.255.255.254 | 2.255.255.255 | 16,777,214 |
| 4 | 3.0.0.0/8 | 3.0.0.0 | 3.0.0.1 | 3.255.255.254 | 3.255.255.255 | 16,777,214 |
| 5 | 4.0.0.0/8 | 4.0.0.0 | 4.0.0.1 | 4.255.255.254 | 4.255.255.255 | 16,777,214 |
| 6 | 5.0.0.0/8 | 5.0.0.0 | 5.0.0.1 | 5.255.255.254 | 5.255.255.255 | 16,777,214 |
| 7 | 6.0.0.0/8 | 6.0.0.0 | 6.0.0.1 | 6.255.255.254 | 6.255.255.255 | 16,777,214 |
| 8 | 7.0.0.0/8 | 7.0.0.0 | 7.0.0.1 | 7.255.255.254 | 7.255.255.255 | 16,777,214 |
| 9 | 8.0.0.0/8 | 8.0.0.0 | 8.0.0.1 | 8.255.255.254 | 8.255.255.255 | 16,777,214 |
| 10 | 9.0.0.0/8 | 9.0.0.0 | 9.0.0.1 | 9.255.255.254 | 9.255.255.255 | 16,777,214 |
| 11 | 10.0.0.0/8 | 10.0.0.0 | 10.0.0.1 | 10.255.255.254 | 10.255.255.255 | 16,777,214 |
| 12 | 11.0.0.0/8 | 11.0.0.0 | 11.0.0.1 | 11.255.255.254 | 11.255.255.255 | 16,777,214 |
| 13 | 12.0.0.0/8 | 12.0.0.0 | 12.0.0.1 | 12.255.255.254 | 12.255.255.255 | 16,777,214 |
| 14 | 13.0.0.0/8 | 13.0.0.0 | 13.0.0.1 | 13.255.255.254 | 13.255.255.255 | 16,777,214 |
| 15 | 14.0.0.0/8 | 14.0.0.0 | 14.0.0.1 | 14.255.255.254 | 14.255.255.255 | 16,777,214 |
| 16 | 15.0.0.0/8 | 15.0.0.0 | 15.0.0.1 | 15.255.255.254 | 15.255.255.255 | 16,777,214 |
FAQ
What is the difference between /4 and /8?
A /4 has 268,435,454 usable hosts
and a /8 has 16,777,214.
The subnet masks differ: /4 uses 240.0.0.0
while /8 uses 255.0.0.0.
Every additional bit in the prefix halves the number of addresses — so the 4-bit gap means
/4 is exactly 16× larger.
How many /8 subnets fit in a /4?
Exactly 16 /8 subnets fit perfectly inside one /4 with no wasted space. To split a /4 into /8s, just increment the last 4 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.