IPRangeExplorer

/12 vs /13 — Subnet Comparison

A /12 subnet is 2× larger than a /13. Every additional bit in the prefix halves the address space — the 1-bit difference between these two means /12 has 21 = 2 times as many addresses.

/12

1 million IPs — the 172.16/12 range

Full reference →
Total IPs 1,048,576
Usable Hosts 1,048,574
Subnet Mask 255.240.0.0
Wildcard Mask 0.15.255.255

Typical Uses

  • →RFC 1918 Class B private range (172.16.0.0/12)
  • →Large enterprise segments
/13
Full reference →
Total IPs 524,288
Usable Hosts 524,286
Subnet Mask 255.248.0.0
Wildcard Mask 0.7.255.255

Key Differences

2×
more IPs in /12 than /13
2
/13 subnets fit inside one /12
1
bit of difference in prefix length

How 2 /13 Subnets Divide a /12

Example using 10.0.0.0/12 as the parent block.

# CIDR Network First Usable Last Usable Broadcast Hosts
1 10.0.0.0/13 10.0.0.0 10.0.0.1 10.7.255.254 10.7.255.255 524,286
2 10.8.0.0/13 10.8.0.0 10.8.0.1 10.15.255.254 10.15.255.255 524,286

FAQ

What is the difference between /12 and /13?

A /12 has 1,048,574 usable hosts and a /13 has 524,286. The subnet masks differ: /12 uses 255.240.0.0 while /13 uses 255.248.0.0. Every additional bit in the prefix halves the number of addresses — so the 1-bit gap means /12 is exactly 2× larger.

How many /13 subnets fit in a /12?

Exactly 2 /13 subnets fit perfectly inside one /12 with no wasted space. To split a /12 into /13s, 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.