IPRangeExplorer

/23 vs /27 — Subnet Comparison

A /23 subnet is 16× larger than a /27. Every additional bit in the prefix halves the address space — the 4-bit difference between these two means /23 has 24 = 16 times as many addresses.

/23

512 IPs — two /24s combined

Full reference →
Total IPs 512
Usable Hosts 510
Subnet Mask 255.255.254.0
Wildcard Mask 0.0.1.255

Typical Uses

  • →Two-floor office network
  • →Expanded department VLAN
  • →Route aggregation of two /24s
/27

30 usable hosts — small workgroup

Full reference →
Total IPs 32
Usable Hosts 30
Subnet Mask 255.255.255.224
Wildcard Mask 0.0.0.31

Typical Uses

  • →Small workgroup LAN
  • →Network device management subnet
  • →Cloud NAT gateway subnet

Key Differences

16×
more IPs in /23 than /27
16
/27 subnets fit inside one /23
4
bits of difference in prefix length

How 16 /27 Subnets Divide a /23

Example using 10.0.0.0/23 as the parent block.

# CIDR Network First Usable Last Usable Broadcast Hosts
1 10.0.0.0/27 10.0.0.0 10.0.0.1 10.0.0.30 10.0.0.31 30
2 10.0.0.32/27 10.0.0.32 10.0.0.33 10.0.0.62 10.0.0.63 30
3 10.0.0.64/27 10.0.0.64 10.0.0.65 10.0.0.94 10.0.0.95 30
4 10.0.0.96/27 10.0.0.96 10.0.0.97 10.0.0.126 10.0.0.127 30
5 10.0.0.128/27 10.0.0.128 10.0.0.129 10.0.0.158 10.0.0.159 30
6 10.0.0.160/27 10.0.0.160 10.0.0.161 10.0.0.190 10.0.0.191 30
7 10.0.0.192/27 10.0.0.192 10.0.0.193 10.0.0.222 10.0.0.223 30
8 10.0.0.224/27 10.0.0.224 10.0.0.225 10.0.0.254 10.0.0.255 30
9 10.0.1.0/27 10.0.1.0 10.0.1.1 10.0.1.30 10.0.1.31 30
10 10.0.1.32/27 10.0.1.32 10.0.1.33 10.0.1.62 10.0.1.63 30
11 10.0.1.64/27 10.0.1.64 10.0.1.65 10.0.1.94 10.0.1.95 30
12 10.0.1.96/27 10.0.1.96 10.0.1.97 10.0.1.126 10.0.1.127 30
13 10.0.1.128/27 10.0.1.128 10.0.1.129 10.0.1.158 10.0.1.159 30
14 10.0.1.160/27 10.0.1.160 10.0.1.161 10.0.1.190 10.0.1.191 30
15 10.0.1.192/27 10.0.1.192 10.0.1.193 10.0.1.222 10.0.1.223 30
16 10.0.1.224/27 10.0.1.224 10.0.1.225 10.0.1.254 10.0.1.255 30

FAQ

What is the difference between /23 and /27?

A /23 has 510 usable hosts and a /27 has 30. The subnet masks differ: /23 uses 255.255.254.0 while /27 uses 255.255.255.224. Every additional bit in the prefix halves the number of addresses — so the 4-bit gap means /23 is exactly 16× larger.

How many /27 subnets fit in a /23?

Exactly 16 /27 subnets fit perfectly inside one /23 with no wasted space. To split a /23 into /27s, just increment the last 4 bits of the network address for each new subnet.

Which should I choose?

/23 is typically used for: Aggregated /24 pair. /27 is better for: Small workgroup / management subnet. Choose the smallest prefix that comfortably fits your host count — over-allocating wastes address space, but under-allocating means painful renumbering later.

Related Comparisons

/24 vs /27 /26 vs /27 /27 vs /28 /23 vs /24